LIBRARY, A 8c M COLLEGE, E CAMPUS. TEXAS AGRICULTURAL EXPERIMENT STATIUN A. B. CONNER, DIRECTOR MARCH 1939 BULLETIN NO. 5'71 DIVISION OF CHEMISTRY The Utilization of the Energy of Feed by Growing Chickens AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS T. O. WALTON, President [Blank Page in Original Bulletin] The productive energy of a feed is its value for furnishing energy to an animal after all losses due to undigested material, metabolic products, and chemical changes of the material have been deducted. To say that a feed has a productive energy of 1.90 calories per gram means that the quantity of feed fed in addition to a ration already suflicient to maintain the chickens produced 1.90 calories in the fat and flesh gained for each gram of feed eaten over main- tenance requirements. The exact estimation of the productive energy of a feed mixture has been determined as a basis with which to compare other feeds. Such comparisons will enable the productive energy of chicken feeds to be com- pared and determined. Eleven experiments were made, involving 256 chicks. .Analyses of the chicks and of the feed, digestion experiments with the feed, and other data were se- cured. Appreciable differences were found in both the weights and composition of some of the chicks fed the same feed for the same period of time, especially in the fat. Maintenance requirements and productive energy calculated on the assumption that maintenance requirements vary according to the weight were found to vary less and to be more in accord with the previous results of other workers than those calculated on the assumption that the maintenance requirements vary according to the surface of the animal. The weight basis was therefore adopted. Individual chickens were found to differ both in their capacity to grow and to utilize feed so that maintenance requirements and productive energy values cal- culated from results from only 2 or 3 animals might not be correct. The use of the average weight by periods gave more concordant results than the average of the first and last weights. Differences in environment, probably temperature, apparently caused differ- ences in maintenance requirements for chickens on the same feed in different experiments. Maintenance requirements for chicks up ‘to the age of about 28 and 42 days averaged, per day per kilogram live weight, 74.8 grams of total feed or 63.3 grams of effective organic constituents, or 48.7 grams of effective digestible nutrients, or 134 calories of productive energy or 200 calories of metabolizable energy. The productive energy of the mixture averaged 1.79 calories per gram for the 10 experiments. The average productive energy of the effective organic con- stituents was 2.14 calories per gram, of the effective digestible nutrients 2.78 calories per gram, and 67.6 per cent of the metabolizable energy was productive energy. On an average, 74.2 per cent of the limited ration was used for main- tenance, and 25.8 was stored as gain of protein and fat, while 42.1 per cent of the full feed ration was used for gain and 57.9 per cent for maintenance. As an average of all the 11 experiments, 40.0% of the total protein eaten was stored by the chicks on full feed and 37.3% by those on limited feed. Of the digestible protein, 56.9% was stored by those on full feed and 52.9 by those on limited feed. The estimated productive value of the digestible protein averaged 71%. The average productive protein required for maintenance was 0.27 gm a day per 100 gm weight. Digestible protein required for maintenance averaged 0.37 gm per day per 100 gm of chicks, while total protein averaged 0.53 gm per day per 100 gm. The experiments indicate that the protein of cereal feeds may have a higher biological value than it has been supposed to have. TABLE OF CONTENTS A Page Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 Productive Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Productive Energy of Chicken Feeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7 Object of the Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7 Method of Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7 Details and Data of the Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8 Variations in the Composition of the Chickens . . . . . . . . . . . . . . . . . . . . .. 18 Basis for Method of Calculating Distribution of Energy between Maintenance and Productive Purposes . . . . . . . . . . . . . . . . . . . . . . . . . .. 19 Calculation of Corrected Maintenance Requirements from the Data. . . . . 25 Corrected Maintenance Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 26 Corrected Productive Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 31 Utilization of the Ration for Maintenance and for Gain . . . . . . . . . . . . . 37 -Utilization of Protein . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 37 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 BULLETIN NO. 571 MARCH 1939 THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS G. S. FRAPS, Chief, and E. G. CARLYLE, Assistant Chemist Division of Chemistry Exact methods for estimating the feeding values of feeds are needed for agricultural and commercial purposes. For agricultural purposes, they are needed in formulating standards for feeding animals, in deciding on rations to be used for feeding purposes, and in studies of the relative economy of various feeding stuffs. For commercial purposes, they are needed for aid in comparing the values of different lots of the same feed or different kinds of feeds with one another, for compounding commercial mixed feeds of the highest possible nutritive value at the lowest possible cost, and for comparing different kinds of commercial mixed feeds with one another. A number of factors affect the value of a feed for animal production. These include the productive energy, the digestible protein, the constitu- ents of the proteins, the various vitamins, chiefly A, D, and G, the minerals, especially lime and phosphoric acid, and in case of ruminants, the bulk, or volume, which helps to satisfy the appetite of the animal. The palatability also appears to be an important factor in inducing the animal to eat liberally of the mixture. The relative importance of these factors in the individual feed depends upon the kind of feed, the kind of animal, and the possible deficiency of ‘the ration to be fed (16). For chickens, productive energy and digestible protein are the most important factors. For ruminants, the bulk or volume must also be considered. In judging the commercial value of unmixed feeds, other factors are con- sidered which are presumably closely related to their feeding values, but perhaps sometimes assigned commercial significance out of proportion to their feeding value. The only one of the factors mentioned above which will be discussed in this bulletin is the productive energy. Productive Energy It was formerly assumed that one pound of the digestible nutrients of one feed was as good as one pound of any other; thus, one pound of digestible nutrients in straw was assumed to be equal in feeding value to one pound of digestible nutrients in corn. It has been shown by Kellner (19), Armsby (1), Forbes and others, that this assumption is not correct. The energy losses consequent to digestion are much greater for each unit of digestible nutrients in straw than in corn, so that the net energy which the animal could secure from a pound of digestible material in corn is much greater than that which it could secure from a pound of digestible 6 BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION material in straw. The ,value of the digestible energy of one kind of feed might be diiferent from that of another kind. Kellner (19) determined the quantities of fat which could be put on by a fattening steer, fed on a slightly fattening ration, by feeding additional quantities of protein, of fat, of starch, of crude fiber, and of sugar. Using the energy values so secured, he calculated the energy values of certain feeds from the digestible constituents and compared the calculated value with the actual quantity of fat put on a fattening steer by additions of these feeds to the ration. With cottonseed meal, peanut oil meal, palm oil meal, and linseed oil meal, he found that the experimental values were prac- tically the same as those calculated, but with other feeds the values found by actual test were decidedly below that calculated. The net energy of Wheat straw was about 20 per cent of that calculated on the assumption that digestible nutrients were equally valuable in all feeds, 63 per cent of that calculated for meadow hay, 69 per cent of that for clover hay, and 77 per cent of that for wheat bran. To put it another way, the assumption of equal value for digestible nutrients would give five times the actual value found by experiment with the Wheat straw, nearly 1.5 times the actual value of meadow hay or clover hay, and 1.3 times the actual value of wheat bran. After establishing the differences in the feeding value of the digestible nutrients of different classes of feeds, Kellner (19) devised methods for estimating and for calculating the productive energy of feeds, and pro- posed feeding standards based upon them. Kellner expressed productive energy in terms of starch. Armsby (1) also proposed standards and devised methods for estimating the productive energy of feeds, expressing the value as therms, a therm being 1,000 large calories. Forbes and associates have continued the Work of Armsby. Kellner’s system has been extensively used in Europe. However, the old system based on the incor- rect assumption that one pound of digestible nutrients in one feed has‘ the same value as one pound in any other feed is still used to a great extent in this country (26). Some deficiencies in the ration may affect its utilization and so decrease the productive energy of feeds, as pointed out by Mitchell (21). Defi- ciencies which may result in a lower productive energy of the ration include sodium chloride for chicks and rats, according to Mitchell and Carman (25); protein for fattening sheep, according to Fraps (14); protein for dairy cows, according to Mollgard as cited by Mitchell (21); protein for rats, according to Mitchell (21); phosphorus for beef heifers, according to Kleiber, Goss, and Guilbert (20); iron and copper for rats, as found by Black et al., (4); sodium for rats, as found by Kahlenberg, Black, and Forbes (18); vitamin G for rats, as found by Braman et al., (5); and lime for sheep, asfound by Jones and Stangel (17). On the other hand, no effect on the productive energy of the ration was indicated by a deficiency of phosphorus in a ration for rats as reported by Forbes (9), or by a deficiency of vitamin A and vitamin B in a ration for rats as reported by Braman et al., (5). THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS 7 Productive Energy of Chicken Feeds The term productive energy, as used in this bulletin, is the same as the calories of energy gained by the chicken for one gram of the feed fed over the maintenance requirements. To say that a feed has a pro- ductive energy of 1.90 calories per gram means that one gram of this ‘ feed, fed in addition to the requirements for maintenance, has produced flesh or fat or other body material containing 1.90 calories. Few data are available upon which to base the absolute productive energy values of chicken feeds. Mitchell and Haines (22) calculated from respiration experiments that the net energy of corn fed to hens was 2.83 calories per gram. Southgate (27) calculated a net energy of 1.8 calories _ per gram for 13 parts ground oats and 3 parts whole dried milk fed cockerels, on the basis of the gain of energy. Fraps (12) has estimated the productive energy of some chicken feeds and given factors to use in calculating the productive energy from the chemical composition, but the data on which these figures are based are very limited. Energy pro- duction coefiicients for ruminants have been published by Fraps (11, 13, 14, 15). Object of the Work The exact determination of the productive energy of some standard samples or mixtures is needed to serve as a basis for the determination and correction of productive energy values of chicken feeds. When the productive energy of a few feeds or mixtures has been determined exactly, other feeds may be compared with them by appropriate methods and a system built up for comparing the ‘productive energy of various chicken feeds. It is much simpler to compare a feed against a standard feed (alone or in a mixture) in order to determine its relative productive energy than to make a direct determination of the productive energy of such feed or mixture. The work presented here has for its object the determination of the productive energy of a mixture of well-known feeds, so that similar mixtures could be used for purposes of comparison with other chicken feeds, and thereby furnish data to ascertain more exactly their productive energy values. Method of Procedure The plan of work is similar to that used by Mitchell (23) with pigs and by Southgate with chickens (27). The procedure was to feed two groups of chickens upon the same feed, one on full feed and the other on limited feed for the same period of time and under the same conditions, ascertain the gain of energy on the two levels of feeding, and from the results to calculate the productive energy of the mixture. The general procedure was as follows: Day-old chickens were placed upon the feed to be tested for a period of about a week. The chickens were then weighed and divided into four groups, three being approximately equal in weight. One group (usually 4) of representative chickens of average weight were killed for analysis. Another group was placed upon full feed, generally ad libitum, 8 BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION and a third group was placed on limited feed, the quantity fed being about half that fed those on full feed and the amount fed daily being based upon previous experience. A fourth group, consisting of the chicks left over after equalizing the other groups, was used for digestion experiments. The chickens were fed individually in battery brooders, each compartment being divided by screen Wire to furnish two spaces each to contain one chicken. The chickens were weighed every week. The feed was Weighed into fruit jars, and weighed quantities fed daily. At the end of the experiment, the weight of the feed remaining served as a check upon the total of the daily weights fed. At the end of the desired period of time, the chickens were killed and analyzed. Digestion experiments were made on the mixtures fed. Several methods of preparing the chickens for analysis were tried. One method consisted in drying the entire chicken and grinding it through a Wiley mill. Any fat which came out was dissolved from the vessel in which the chicken was dried and weighed separately. The dried chicken was found to be so hygroscopic as to take up moisture during the process of grinding and analysis, and in this respect the method was not satis- factory, since several corrections were necessary. Extracting the chicken with ether and then drying and grinding the residue was tried and found to be complicated and liable to error on account of changes in moisture. The method finally adopted was to grind the entire chicken as finely as possible through a meat chopper, with the addition of about 1 per cent boric acid. The sample was left in cold storage and the analysis made by three different analysts as quickly as possible. There was some difii- culty due to liquid settling out after three or four days. This method has since been improved by the addition of ground filter paper at the time of preparation, which not only enables the sample to be ground more finely, but also prevents liquid from settling out. This improvement had not been devised at the time the work here reported was completed. Nitrogen was determined by the Kjeldahl-Gunning method on 3.5 gm portions. In all the analyses, protein was considered to be nitrogen x 6.25. Fat was determined on 4 gm portions by extraction with ether after drying under reduced pressure at 100°C. and grinding in a mortar. Calories were calculated by multiplying protein by 5.66 and ether extract by 9.35. Details and Data of the Experiments The results of eleven experiments are reported. In the first four experiments, 4 chickens were used in each of the two lots; in 5 experi- ments, 10 chickens were used in each lot; and in 2 experiments, 8 chickens were used per lot. Including the preliminary chicks used to ascertain their composition at the beginning of the experiment, the total number of chicks killed was 256. The mixtures used in all the experiments were similar, but since the experiments were carried on over a period of several years, it was necessary to use several different lots of the same kind of feed. Table 1 shows the ingredients of mixtures used. The analyses of the feeds used for each THE UTILIZATION OF THE ENERGY OF FEED BY GROWING GHICKENS 9 mixture are given in Table 2. The composition of the mixtures was ascertained both by calculation from the data in Tables 1 and 2 and by analysis of the mixtures, and these are compared in Table 3. On the whole, the agreement is satisfactory. Table 1. Ingredients of the mixtures, in per cent. Laboratory Mixture Mixture Mixture Mixture Mixture Mixture number Name of feed 14 18 22 23 24 25 33918 Yellow corn meal. . . . . 51.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37338 Yellow corn meal . . . . . . . . . . . . . . . . . . . . . 51 .0 51 .0 . . . . . . . . . . . . . . . . 39146 Yellow corn meal... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 .0 . . . . . . . . 39393 Yellow corn meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 .0 35916 Yellow corn feed meal. . . . . . . . . 51 .0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35673 Wheat gray shorts. . . . 19.0 19.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37336 Wheat gray shorts. . . . . . . . . . . . . . . . . . . . 19.0 19.0 . . . . . . . . . . . . . . . . 39145 Wheat gray shorts... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.0 19.0 33972 Dried buttermilk. . . . . 10.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35917 Dried buttermilk . . . . . . . . . . . . . 10.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37340 Dried buttermilk . . . . . . . . . . . . . . . . . . . . . 10.0 10.0 10.0 . . . . . . . . 39396 Dried buttermilk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.0 35675 Cottonseed meal. . . . . 6.0 6.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37337 Cottonseed meal . . . . . . . . . . . . . . . . . . . . . 6.0 . . . . . . . . . . . . . . . . . . . . . . . . 37509 Cottonseed meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.0 6.0 . . . . . . . . 39412 Cottonseed meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.0 33973 Alfalfa leaf meal . . . . . . 5 .0 5. 5.0 5.0 . . . . . . . . . . . . . . . . 37641 Alfalfa leaf meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.0 5.0 32790 Tankage............. 4.0 4. 4.0 4.0 4.0 . . . . . . .. 39395 Tankage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.0 33303 Bone meal . . . . . . . . .. 2.0 2. 2.0 2.0 2.0 2.0 33304 Oyster shell . . . . . . . . . 2.0 2.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37339 Oyster shell . . . . . . . . . . . . . . . . . . . . . . . . . 2.0‘ 2.0 2.0 2.0 Salt . . . . . . . . . . . . . . .. 1.0 1.0 1.0 1.0 1.0 1.0 Cod liver oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0. 1 Table 2. Percentage composition of ingredients of mixtures. Laboratory _ Ether Crude Nitro- number Name of feed Protein extract fibre gen free NVater Ash extract 33918 Yellow corn meal... . . 10.20 4.40 2.64 72.07 9.43 1.26 37338 Yellow corn meal... . . 9.86 4.10 1.82 73.89 9.19 1.14 39146 Yellow corn meal... . . 10.05 4.12 2.21 70.75 11.69 1 .18 39393 Yellow corn meal... . . 9.62 3.49 2.50 70.59 12.29 1.51 35916 Yellow corn feed meal. 9 .86 4.21 2 .02- 71.04 11.58 1 .29 35673 Wheat gray shorts... . 18.25 4.52 6.77 55.45 10.38 4.63 37336 Wheat gray shorts... . 20.08 4.88 6.45 53.34 10.68 4.57 39145 Wheat gray shorts... . 19.32. 4.91 5.81 55.23 10.31 4.42 33972 Dried buttermilk. . . . . 47 .33 8.60 .18 31.55 5.97 6.37 35917 Dried buttermilk. . . . . 33.44 5.23 .76 38.69 11.03 10.85 37340 Dried buttermilk. . . . . 37.10 6.06 .69 27 .85 13.51 14.79 39396 Dried buttermilk. . . . . 34.78 5.72 .22 42.13 6.39 10. 76 35675 Cottonseed meal. . . . . 42.47 7.50 10.16 27.32 6.68 5.87 37337 Cottonseed meal. . . . . 46 .34 7.87 9.98 23.81 5.72 6.28 37509 Cottonseed meal. . . . . 47.33 6.21 9.70 24.20 6.40 6.16 39412 Cottonseed meal . . . . 45.35 7.72 10.70 24.53 5.74 5.96 33973 Alfalfa leaf meal . . . . . . 20.68 2.34 16.67 42.56 7.41 10.34 37641 Alfalfa leaf meal . . . . .. 21.79 3.17 17.27 40.71 5.70 11.36 32790 Tankage . . . . . . . . . . .. 51.89 9 .20 1.59 3.15 5 .21 28. 96 39395 Tankage . . . . . . . . . . . . 59.21 8.36 1 .54 2 .46 5.88 22.55 33303 Bone meal . . . . . . . . .. 25.56 1.73 0 4.51 6.37 61 .83 The effective organic constituents are also given in Table 3. These consist of the sum of the protein, the ether extract multiplied by 2.25, and the nitrogen-free extract. The ash, water, and crude fiber are con~_ sidered to have no value as sources of energy in chicken feeds. 10 BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION Table 3. Percentage composition of mixtures as calculated from the ingredients and analyses in Tables l and 2 and as found by analysis, and efiective organic constituents. Effective Mix. _ _ Ether Crude Nitro- organic N0. Protein extract fibre gen free Water Ash constit- extract uents Found . . . . . . . . . .. 14 19.65 5.05 4.00 55.56 8.30 7.44 86.6 Calculated . . . . . . . . 14 19.56 4.93 4.16 55 .31 8.49 7.55 . . . . . . . . Found . . . . . . . . . .. 18 18.55 4.64 3.90 56.18 8.93 7.80 . . . . . . .. Found . . . . . . . . . .. 18 18.56 4.70, 3.79 55.78 9.17 8.00 . . . . . . .. Found.. . . . . . . . .. 18 18.77 4.66 3.72 56.55 8.31 7.99 . . . . . . .. Found . . . . . . . . . .. 18 18.83 4.62 3.84 56.32 8.58 7.81 . . . . . . .. Average (4) . . . . . . . . . . . .. 18.68 4.66 3.81 56.21 8.75 7.90 85.4 Calculated........ 18 18.01 4.50 3.90 55.43 10.07 8.09 . . . . . . .. Found . . . . . . . . . .. 22 19 22 4.42 3.79 55.13 9.10 8.34 . . . . . . .. Found . . . . . . . . . .. 22 19.64 4.60 3.73 55.37 7.97 8.69 . . . . . . .. Average (2) . . . . . . . . . . . .. 19.43 4.51 3.76 55.25 8.54 8.52 84.8 Calculated . . . . . . . . 22 18.96 4.62 3.72 54.98 9.31 8.43 . . . . . . . . Found . . . . . . . . . .. 23 19.31 4.51 3.85 55 35 8.37 8.61 84.8 Calculated . . . . . . . . 23 19.02 4.52 3.70 55 00 9.36 8.42 . . . . . . . . Found . . . . . . . . . .. 24 18.75 4.43 3.99 53.24 10 53 9.06 82.0 Calculated. . .. . . .. 24 19.03 4.57 3.80 53.67 10 48 8.45 . . . . . . .. Found . . . . . . . . . .. 25 18.90 4.50 3.92 55.39 8.69 8.60 84.4 Calculated . . . . . . . . 25 18.75 4.26 3.96 55.00 10.07 7.96 . . . . . . . . The digestion coeflicients of the mixtures, as found by digestion experi- ments similar to those used in the other parts of this work, are given in Table 4. This table also contains the digestibility calculated from the constituents of the mixtures and digestion coeflicients (also given in Table 5) taken from Texas Bulletin 3'72 (12). The digestibility of the protein and nitrogen-free extract of the mixtures as found by experi- ment are appreciably lower than the digestibility calculated by use of the coeflicients in Table 5. Part of these differences may be due to the fact that the coeflicients of digestibility in Bulletin 372 are averages of individual experiments, which vary; and some deviation of an individual experiment from the average is to be expected. It is also possible that young chickens digest somewhat differently from the older ones used to secure the coefficients of digestibility employed in the calculations. Table 4 also contains the effective digestible nutrients,- which are the digestible protein, plus the digestible ether extract multiplied by 2.25, and the digestible nitrogen-free extract. The digestible crude fiber is not considered to be of value as a source of energy for chickens. The live weight, empty weight, weight after preparation, the percentage of protein and fat, and the calories per 100 gm calculated from the composition are given for each chicken in Table 6. The empty weight is the weight of the chicken after the contents of the intestinal tract have been removed. There is always some loss in preparation of the sample, due to adhesion to the feed chopper and other things with which the sample comes into contact during the preparation, and also possibly due, in small part, to evaporation of water. The percentage of protein and fat are on the original basis, after correction has been made for the THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS 11 Table 4. Digestion coefficients as found by experiment and as calculated from assumed digestibility of the ingredients as given in Table 5, effective digestible nutrients and estimated metabolizable energy. Estimated _ Effective metaboliz- Ether Crude Nitrogen digestible able Mix Protein extract fibre free nutrients, energy, extract per cent calories of feed per gram D. E. 96 . . . . .. 14 72.72 87.58 5.91 74.94 65.8 2.70 Calculated. . . . . . . . .. 77.56 86.04 11.30 81.90 . . . . . . . . . . . . . . . . . . . . Difference . . . . . . . . . . . —4.84 +1 .54 ———5.39 —6.96 . . . . . . . . . . . . . . . . . . . . D. E. 98 . . . . .. 18 73.53 89.29 12.01 76.31 . . . . . . . . . . . . . . . . . . .. D. E. 99 . . . . .. 18 71.78 90.32 13.16 78.32 . . . . . . . . . . . . . . . . . . .. D. E. 100.. 18 66.34 86.24 0 73.08 . . . . . . . . . . . . . . . . . . .. D. E. 101... 18 66.39 86.31 2.34 75.09 . . . . . . . . . . . . . . . . . . .. Average (4) . .. . . . . .. 69.51 88.04 6.88 75.70 64.8 2.66 Calculated. . .. . . . . .. 77.29 86.22 11.02 81.91 . . . . . . . . . . . . . . . . . . . . Difference . . . . . . . . . .. ——7.78 +1.82 ——4. 14 ~—6.21 . . . . . . . . . . . . . . . . . . . . D. E. 102..... 22 73.88 95 54 15.34 76.32 . . . . . . . . . . . . . . . . . . .. D. E. 103..... 22 3.37 93 23 16.62 77.50 . . . . . . . . . . . . . . . . . . .. D. E. 104..... 22 71.80 94 14 12.56 77.79 . . . . . . . . . . . . . . . . . . .. D. E. 105..... 22 72 45 93 29 6.95 76.08 . . . . . . . . . . . . . . . . . . .. Average (4). . . . . . . . . 72 88 94 05 12.87 76.92 66.2 2.71 Calculated. . . . . . . . . . 75 26 81 80 10.22 83.89 . . . . . . . . . . . . . . . . . . . . Difference. . . . . . . . . . ——2 38 12 25 2.65 —-6.97 . . . . . . . . . . . . . . . . . . . . D. E. 106..... 23 69.07 93 74 17.89 78.75 . . . . . . . . . . . . . . . . . . .. D. E. 107..... 23 71.36 92 97 12.80 78.38 . . . . . . . . . . . . . . . . . . .. Average (2). . . . . . . . . 70.22 93 36 15.35 78.57 66.5 2.73 Calculated. . . . . . . . . . 75.24 86 73 10.27 83.89 . . . . . . . . . . . . . . . . . . . . Difference . . . . . . . . . . . -—5 02 6 63 5.08 —5 .32 . . . . . . . . . . . . . . . . . . . . D. E. 108..... 24 70.33 95 19 19.87 77.00 . . . . . . . . . . . . . . . . . . .. D. E. 109..... 24 66.56 89 19 21.62 76.11 . . . . . . . . . . . . . . . . . . .. Average (2). .. . . . . .. 68.45 92 19 20.75 76.56 62.8 2.58 Calculated. . .. . . . . . . 75 20 85 78 10.66 83.64 . . . . . . . . . . . . . . . . . . . . Difference . . . . . . . . . . . —6 75 6 41 10.09 —7.08 . . . . . . . . . . . . . . . . . . . . D. E.110..... 25 65 76 85 70 11.57 78.58 66.5 2.73 Calculated. . . . . . . . . . 75 31 85 68 10.61 83.60 . . . . . . . . . . . . . . . . . . . . Difference . . . . . . . . . . . ——9 55 02 .96 —5.02 . . . . . . . . . . . . . . . . . . . . Table 5. Digestion coefficients used for the individual feed (from Texas Bul. 372). Nitrogen Protein Ether Crude free extract fibre extract Corn feed meal . . . . . . . . . . . . . . . . . . . . . . . . . .. 71.8 91 .6 15.2 91.9 Dried buttermilk . . . . . . . . . . . . . . . . . . . . . . . . . . 81 .6 78.6 . . . . . . . . . . 81 . 1 43% Protein cottonseed meal . . . . . . . . . . . . . . . 76. 1 86.2 11 .9 85 .7 Alfalfa meal . . . . . . . . . . . . . . . . . . . . . . . . . .. '. .. 63.4 21.8 1.4 34.4 Wheat gray shorts . . . . . . . . . . . . . . . . . . . . . . . . 69.2 85.2 13.0 71.0 Tankage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 85.3 95.9 4.0 43.5 Bone meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 86.7 93.1 24.0 34.0 quantity of boric acid added. Small percentages of nitrogen-free extract are sometimes present, if estimated by difference, but this is not given or considered. In averaging the calories per gram of the preliminary 12 BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION chicks, occasionally one of the chicks is omitted, on account of it deviating too far from the others. Those omitted are marked in the tables. The calorie contents of the chicks at the beginning are calculated from the analyses of the preliminary chicks. The average calorie content of these chicks is multiplied by the average empty Weight and this is divided by the live weight to secure the average calorie content per gram of live weight. The calorie content of the other chicks at the beginning of the experiment is calculated by multiplying the live Weight at the beginning by the calorie content per gram of live Weight of the preliminary chicks. The average data of the experiments are summarized in Tables 10 and 11. These data are used to calculate the average maintenance require- ments of the chicks and the average productive energy of the feed. Detailed data are given in Tables 6, 15, and 18. Table 6. Composition, weights and calories per 100 grams for individual chickens. Live Live Empty Per cent Weight Calories, weight weight weight empty after Protein Fat per 100 Series and Laboratory at be- at end at end weight prepara- per cent per cent gm. num er ginning gm. gm. of live tion empty gm. weight gm. weight Series 50 Preliminary 35686 56 1 49.5 88.24 47 3 17.80 7.25 175.5 35687 . . . . . . . . . . . . . . . . .. 50 0 41.7 83.40 40 5 17.36 6.59 165.3 35688 . . . . . . . .. 55 1 49.0 88.93 46 1 16.65 7.44 172.4 35689 49 8 44 1 88.55 42 5 17.33 6.16 159.5 Average . . . . . . . . . . . . . . . . .. 52.8 6 1 88.57 . . . . . . . .. 17.29 6.86 171.1 Calories per 100 grams . . . . . . . . . . . . . 151.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Full feed 35715 . . . . . . . . . . . . . . . . .. 49 7 144.1 136.5 94.73 134 3 20 00 10.31 211.5 35716 . . . . . . . . . . . . . . . . .. 56 8 174.5 165.1 94.61 161 3 19 82 11.77 227.5 35717 . . . . . . . . . . . . . . . . .. 52_.4 152.5 141.0 92.46 138.5 20.74 8.99 206.3 35718 . . . . . . . . . . . . . . . . .. 59.8 188.9 182.8 96.77 175.0 20.00 10.41 219.8 Average . . . . . . . . . . . . . . . . .. 54.7 165.0 156.4 94.64 . . . . . . . .. 20.14 10.37 216.3 Limited feed . 35719 . . . . . . . . . . . . . . . . .. 55.8 117.5 112.1 95.40 110.0 19.61 7.27 184.6 35720 . . . . . . . . . . . . . . . . .. 53 2 114 1 103.4 90.62 102 2 20 31 7 00 186 4 35721 . . . . . . . . . . . . . . . . .. 52.2 110.0 103.5 94.09 102.9 19.15 5. 171.1 35722 . . . . . . . . . . . . . . . . .. 54.5 112.1 101.5 90.54 95.5 20.81 5.48 176.0 Average . . . . . . . . . . . . . . . . .. 53.9 113.4 105.1 92.66 . . . . . . . .. 19.97 6.32 179.5 Series 51 Preliminary 35738 . . . . . . . . . . . . . . . . . . . . . . . . . .. 60.5 53.6 88.60 51 3 17.75 7.80 179.0 35739 . . . . . . . . . . . . . . . . . . . . . . . . . .. 52.3 46.8 89.48 45 6 18.08 6.57 166.8 35740 . . . . . . . . . . . . . . . . . . . . . . . . . .. 62.1 56.5 90.98 53 2 17.12 9.16 187 6 35741 . . . . . . . . . . . . . . . . . . . . . . . . . .. 59.5 53.6 90.08 52.4 18.37 7.24 171.7 Average . . . . . . . . . . . . . . . . . . . . . . . . . . . 58.6 52. 6 89.79 . . . . . . . . . 17.83 7.69 176.3 Caliiriesdper 100 grams . . . . . . . . . . . . . 158.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . e 53.3 171 9 156.5 91.04 150 9 19.86 8.57 197.0 62.3 202 1 172.4 85.30 170 5 19.71 9.06 199.9 56.0 185 9 174.0 93.60 173 0 20.67 10.18 212.6 64.6 185 8 172.0 92.57 8 20.33 9.22 202.2 59.1 186 4 168.7 90.63 . . . . . . . .. 20.14 9.26 202.9 61.6 124 5 106.1 85.22 104 3 20.84 4.63 169.2 57.4 118 2 103.6 87.65 102 1 20.78 4.85 167.6 59.8 132 4 121.1 91.47 117 6 20.29 4.22 162.6 53.3 113.9 104.5 91.75 100 2 20.29 3.89 160.7 Average . . . . . . . . . . . . . . . . . . 58.0 122 .3 108.8 89 .02 . . . . . . . . . 20.55 4.40 165.0 THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS 13 Table 6-—continued. Composition, weights and calories per 100 grams for individual chickens. Live Live Empty Per cent Weight _ Calories, weight weight weight empty after Protein Fat per 100 Series and Laboratory at be- at end at end weight prepara- per cent per cent gm. number ginning gm. gm. of _l1ve tion empty gm. weight gm. weight Series 52 Preliminary 35935 . . . . . . . . . . . . . . . . . . . . . . . . . .. 51.0 45.7 89.61 42.4 16.53 6.53 154.6 35936 . . . . . . . . . . . . . . . . . . . . . . . . . .. 48.0 43.5 90.63 42.3 16.98 6.40 156.0 35937 . . . . . . . . . . . . . . . . . . . . . . . . . .. 40.7 37.2 91.40 34.7 16.65 5.39 144.6* 35938 . . . . . . . . . . . . . . . . . . . . . . . . . .. 49.2 45.8 93.09 44.2 16.99 6.73 160.0 Average . . . . . . . . . . . . . . . . . . . . . . . . . . . 47.2 43.1 91.18 . . . . . . . .. 16.79 6.26 156.6 Calories per 100 grams . . . . . . . . . 142.7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Full feed 36083 . . . . . . . . . . . . . . . . .. 50.5 377.0 352.4 93.47 342.0 21.20 9.10 205.1 36084 . . . . . . . . . . . . . . . . .. 49.0 320.6 299.8 93.51 291.0 21.82 10.16 218.5 36085 . . . . . . . . . . . . . . . . . . 45.4 372.1 356.5 95.81 347.2 21.52 8.34 199.8 36086 . . . . . . . . . . . . . . . . .. 45.7 303.1 288.5 95.18 283.5 21.88 5.85 178.5 Average . . . . . . . . . . . . . . . . . . 47.7 343.2 324.3 94.49 . . . . . . . . . 21 61 8.36 200.5 Limited feed 36095 . . . . . . . . . . . . . . . . . . 49.6 194.5 170.0 87.40 166.2 23.00 3.51 163 .0 36096 . . . . . . . . . . . . . . . . .. 49.0 214.7 191.8 89:33 _ 186.5 22.02 5.44 175.5 36097 . . . . . . . . . . . . . . . . .. 41.8 168.5 156.1 92.64 152.0 22.90 2.44 152.4 36098 . . . . . . . . . . . . . . . . .. 47.1 191.7 179.2 93.48 174.0 23.07 2.64 155.3 Average . . . . . . . . . . . . . . . .. 46.9 192.4 174.3 90.71 . . . . . . . .. 22.75 3 .51 161.5 68 0 17.51 8.99 183.2 64.9 18.49 7.05 170.6‘ 74.1 18.77 8.85 189.0 67.6 18.07 8.71 183.7 Average . . . . . . . . . . . . . . . . . . 68.7 18.21 8.40 185.3 Calories per 100 grams . . . . . . . . . . . . . 165.7 . . . . . . . . . . . . . . . . . . . . . . . . . . . l Feed 36262 . . . . . . . . . . . . . . . . . . 72.6 361.5 347.0 95.99 337.8 21.45 9.93 214.3 36264 . . . . . . . . . . . . . . . . .. 62 7 355.0 333.0 93.80 327.8 21.34 10.18 216.0 36265 . . . . . . . . . . . . . . . . . . 71 1 311.0 294.2 94.60 296.5 22.38 6.90 191.2 36266 . . . . . . . . . . . . . . . . . . 64.9 368.0 350.2 95.16 342.3 21.39 11.73 230.8 Average . . . . . . . . . . . . . . . . .. 67.8 348.9 331.1 94.89 . . . . . . . .. 21.64 9.69 213.0 Limited feed 362 . . . . . . . . . . . . . . . . .. 70.0 211.3 188.0 88.97 183.2 21.83 3.96 160.6 936276 . . . . . . . . . . . . . . . . .. 67.1 214.5 191.5 89.28 187.4 22.75 3.70 163.4 36277 . . . . . . . . . . . . . . . . .. 70.0 197.8 174.5 88.22 169.2 21.80 2.84 149.9 36278 . . . . . . . . . . . . . . . . . . 63.0 194.3 183.8 94.60 184.0 22.11 3.83 161.0 Average . . . . . . . . . . . . . . . . . . 67.5 204.5 184.5 90.27 . . . . . . . . . 22.12 3 .58 158.7 Series 55 Preliminary 37354 . . . . . . . . . . . . . . . . . . . . . . . . . .. 50.2 45.4 90.44 42.1 17.80 8.41 179.4 49.4 43.5 88.06 41.2 17.44 6.29 157.5 53.4 46.5 87.08 44 2 17.26 7.04 163.5 45.4 39.4 86.78 37.2 16.25 6.03 148.4 49.6 43.7 88.09 . . . . . . . .. 17.19 6.94 162.2 143.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ull feed 37372 . . . . .. . . . . . . . . . . .. 56.4 195.0 181.9 93 .28 172.2 20.85 9.33 205.3 37373 . . . . . . . . . . . . . . . . .. 51.3 225.5 205.7 91.22 201.7 20.18 13.58 241.2 37374 . . . . . . . . . . . . . . . . . . 54.0 216.2 199.5 92.28 194.5 20.75 9.62 207.4 37375 . . . . . . . . . . . . . . . . . . 58.4 234.2 220.8 94.28 213 .5 19.46 12.10 223.3 37376 . . . . . . . . . . . . . . . . . . 47.1 190.5 181.2 95.12 175.9 20.58 11.39 223.0 37377 . . . . . . . . . . . . . . . . . . 55.5 240.7 223.0 92.65 213.7 20.73 10.95 219.7 37378 . . . . . . . . . . . . . . . . .. 42.6 162.7 153.2 94.16 151.5 20.87 11.67 227.2 37379 . . . . . . . . . . . . . . . . .. 41.2 173.7 165.5 95.28 161.7 19.52 12.53 227.6 37380 . . . . . . . . . . . . . . . . .. 54.8 214.5 201.7 94.03 194.3 21.00 11.57 227.0 37381 . . . . . . . . . . . . . . . . . . 56.5 193.9 182.7 94.22 176.9 21.43 10.91 223.3 Average . . . . . . . . . . . . . . . . . . 51.8 204.7 191.5 93.65 . . . . . . . . . 20.54 11.37 222.5 Limited feed 37382 . . . . . . . . . . . . . . . . .. 56.2 121.2 108.5 89.52 105.2 21.03 7.27 187.0 37383 . . . . . . . . . . . . . . . . . . 50.3 121.8 108.2 88.83 105.5 20.50 4.85 161.4 37384 . . . . . . . . . . . . . . . . .. 54.2 114.7 103.0 89.80 99 .3 20.95 3.98 155.8 37385 . . . . . . . . . . . . . . . . .. 58.9 112.9 101.5 89.90 97.8 20.85 3.08 146.8 ‘Omitted from average. 14 BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION Table 6-—continued. Composition, weights and calories per 100 grams for individual chickens. Live Live Empty Per cent Weight Calories, weight weight weight ernpty after Protein Fat per 100 Series and Laboratory qt at end at end weight prepara- per cent per cent gm. number ginning gm. gm. of _l1ve t1on empty gm. weight gm. weight Limited feed—continued 37386 . . . . . . . . . . . . . . . . .. 47.0 126.7 112.5 88.79 106.2 21.25 4.47 162.1 37387 . . . . . . . . . . . . . . . . .. 55.5 106.3 96.5 90.78 91.8 21.38 3.82 156.7 37388 . . . . . . . . . . . . . . . . .. 41.4 113.7 101.2 89.01 95.5 20.40 6.44 175.7 37389 . . . . . . . . . . . . . . . . . . 41.4 123.5 102.5 83.00 99.1 20.60 6.45 176.9 37390 . . . . . . . . . . . . . . . . . . 56.2 119 2 105.2 88.26 99.2 21.24 4156 162.9 37391 . . . . . . . . . . . . . . . . .. 56.2 111 8 104.8 93.74 100.7 21.31 3.47 153.1 Average . . . . . . . . . . . . . . . . .. 51.7 117 2 104.4 93.65 . . . . . . . .. 20.95 4.84 163.8 Series 56 Preliminary 37448 . . . . . . . . . . . . . . . . . . . . . . . . . .. 43.7 40.0 91.53 37.3 15.44 7.38 156.4 37449 . . . . . . . . . . . . . . . . . . . . . . . . . .. 47.7 41.9 87.84 39.8 17.57 6.85 163.5 37450 . . . . . . . . . . . . . . . . . . . . . . . . . .. 51.5 47.5 92.23 45.5 16.64 8.28 171.6 37451 . . . . . . . . . . . . . . . . . . . . . . . . . . . 46.6 41.5 89.06 39.5 16.86 7.21 162.8 Average . . . . . . . . . . . . . . . . . . . . . . . . . . . 47.4 42.7 90.17 . . . . . . . .. 16.63 7.43 163.6 Calories per 100 grams . . .1 . . . . . . . . . . 147. 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Full feed 45.0 169.6 166.5 98.17 159.3 20.40 10.58 214.4 44.9 ‘ 199.5 188.5 94.49 181.5 20.18 9.19 200.2 51.5 235.2 217.0 92.26 210.4 19.74 9.90 204.3 49.4 201.1 186.3 92.64 181.0 20.56 10.47 214.3 52.9 166.7 153 .‘5 92.08 146.4 22.39 8.58 207.0 48.2 210.2 196.9 93.67 186.6 21.21 10.94 222.3 45.4 187.4 175.5 93.65 167.4 20.68 8.24 194.1 51.0 183.8 170.5 92.76 161.5 20.78 8.34 195.6 49.5 201.8 190.7 94.50 181.6 20.55 9.71 207.1 42.3 196.2 185.8 94.70 176.9 21.35 10.36 217.3 48.0 195 2 183.1 . . . . . . . . . . . . . . . . .. 20.78 9.63 207.7 45.3 114.7 99.0 86.31 95.3 21.02 5.11 166.8 45.4 113.6 98.5 86.71 93.5 20.66 4.50 159.0 51.0 104.7 93.0 88.83 89.5 21.77 3.35 154.5 48.2 113.0 103.2 91.33 98.9 20.89 5.07 165.6 52.2 105.7 94.7 89.59 91.5 21.50 3.45 154.0 48.4" 100.2 90.2 90.02 87.5 21.90 3.31 154.9 52.2 116.2 103.2 88.81 97.3 20.47 4.32 156.3 50.0 109.8 98.2 89.44 89.9 20.51 5.26 165.3 49.5 119.8 106.5 88.90 100.4 20.88 3.80 153.7 42.8 106.3 93.7 88.15 88.1 21.66 2.80 148.8 Average . . . . . . . . . . . . . . . .. 48.5 110.4 98.0 . . . . . . . . . . . . . . . . .. 21.13 4.10 157.9 Series 57 Preliminary 37568 . . . . . . . . . . . . . . . . . . . . . . . . . .. 56.5 49.1 86.90 48.0 16.79 8.56 175.1 50.8 44.7 87.99 42.3 16.98 8.44 175.0 52.5 49.0 93.33 46.2 17.76 9.39 188.3 55.4 50.1 90.43 47.0 17.97 8.57 181.8 Average . . . . . . . . . . . . . . . . . . . . . . . . . .. 53 .8 48.2 89.66 . . . . . . . .. 17.38 8.74 180.1 Calories per 100 grams . . . . . . . . . . . . . 161.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Full feed 37620 . . . . . . . . . . . . . . . . .. 51.1 448.0 426.5 95.20 404.2 23.00 9.67 220.6 37621 . . . . . . . . . . . . . . . . .. 52.1 375.5 359.6 95.77 339.5 22.97 11.40 236.6 37622 . . . . . . . . . . . . . . . . .. 54.0 434.5 400.7 92.22 380.0 23.10 7.48 200.7 37623 . . . . . . . . . . . . . . . . .. 53.0 464.2 440.0 94.79 418.7 22.31 11.72 235.9 37624 . . . . . . . . . . . . . . . . .. 56.5 431.0 400.7 92.97 382.3 22.40 9.79 218.3 37625 . . . . . . . . . . . . . . . . .. 52.4 402.5 356.5 88.57 346.5 23.60 7.84 206 .9 37626 . . . . . . . . . . . . . . . . .. 49.4 391.5 370.2 94.56 354.2 23.28 9.40 219.7 37627 . . . . . . . . . . . . . . . . . . 50.0 534.0 492.1 92.15 469 .3 22.01 10.99 227.3 37628 . . . . . . . . . . . . . . . . .. 54.6 464.5 394.5 84.93 376.7 21.57 7.87 195.7 37629 . . . . . . . . . . . . . . . .. 52.5 438.0 406.7 92.85 393.6 21.56 12.77 241.4 Average . . . . . . . . . . . . . . . . . . 52.6 438.4 404.8 92.40 . . . . . . . . . 22.58 9.89 220.3 Limited feed 37630 . . . . . . . . . . . . . . . . .. 51.8 147.1 135.5 92.11 129.7 22.30 3.27 156.8 37631 . . . . . . . . . . . . . . . . .. 52.1 173.0 158.5 91.62 153.1 22.43 3.95 163.9 37632 . . . . . . . . . . . . . . . . .. 54.0 157.2 142.5 90.65 135.8 23 .55 3.20 163.2 37633.1 . . . . . . . . . . . . .. 50.0 139.1 128.2 92.16 127.0 22.06 3.08 153.7 37634 . . . . . . . . . . . . . . . . . . 56.6 181.2 172.5 95.20 168.6 22.42 2.98 154.8 37635 . . . . . . . . . . . . . . . . . 52.4 155.5 145.2 93.38 139.3 22.51 2.47 150.5 THE UT1LIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS 15 Table 6—continued. Composition, weights and calories per 100 grams for individual chickens. Live Empty Weight Calories, weight weight after Protein Fat per 100 Series and Laboratory at end at end prepara- per cent per cent gm. num i r gm. gin. tion empty gm. gm. weight Limited Ieed-—continued 37636 . . . . . . . . . . . . . . . .. 205.5 193.0 191.3 22.85 3 .67 163.6 167.3 158.2 153.6 23.18 2.97 159.0 173.9 161.0 155.4 22.18 3.74 160.5 176.2 167.5 162.0 22.27 4.08 164.2 167.6 156.2 . . . . . . .. 22.58 3.34 159.0 689 . . . . . . . . . . . . . . . . .. 65.5 57.8 88.24 50.1 18.49 8.80 186.9 37690 . . . . . . . . . . . . . . . . .. 68.5 60.8 88.76 56.3 18.57 8.76 186.6 37691 . . . . . . . . . . . . . . . . .. 64.2 57.5 89.56 53.1 18.23 11.10 207.0* 37692 . . . . . . . . . . . . . . . . .. 66.5 63.5 95.49* 58.7 18.72 8.65 186.8 Average. . . . . . . . . . . . . . . . . 66.2 59.9 88.85 . . . . - . . .. 18.50 9.36 186.8 Calories per 100 grams . . . . . . 166.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Full feed 37702 . . . . . . . . . . . . . . . . .. 65.0 223.7 211.1 94.37 204.3 20.02 10.26 209.2 37703 . . . . . . . . . . . . . . . .. 68 2 220.8 211.5 95.79 204.3 20.86 10.18 213 3 37704 . . . . . . . . . . . . . . . . .. 62.5 201.5 188.8 93.70 178.9 20.88 9.96 211.3 37705 . . . . . . . . . . . . . . . . .. 66.8 163.0 158.7 97.36 154.5 23 .84 6.96 200.0 37706 . . . . . . . . . . . . . . . . .. 65.8 243.2 226.5 93 13 221.4 20.98 8.07 194.2 37707 . . . . . . . . . . . . . . . . .. 62.5 204.5 192.1 93 .94 190.5 20.06 9.03 198.0 37708 . . . . . . . . . . . . . . . . .. 68.5 233.0 228.5 98.07 225.0 21.06 10.20 215.3 37709 . . . . . . . . . . . . . . . . .. 61.9 209.5 200.5 95.70 196.8 20.80 9.40 205.6 37710 . . . . . . . . . . . . . . . . .. 64.0 186.5 170.5 91.42 165.2 21.55 6.64 184.1 37711 . . . . . . . . . . . . . . . . .. 66.5 221.0 208.7 94.43 204.5 20.98 8.32 196.5 Average . . . . . . . . . . . . . . . .. 65.2 210.7 209 7 94.79 . . . . . . .. 21.10 8.91 202.8 Limited feed 37712 . . . . . . . . . . . . . . . . .. 64.8 113.3 101.5 89.59 96.8 21.56 3.51 154.9 37713 . . . . . . . . . . . . . . . . .. 68.5 113.5 99.1 87.31 97.3 22.06 2.58 149.0 37714 . . . . . . . . . . . . . . . . .. 61.6 106.2 94.6 89.08 92.4 21.42 3.57 154.6 37715 . . . . . . . . . . . . . . . .. 67.4 96.5 86.2 89.33 83.8 22.15 1.53 139.7 37716 . . . . . . . . . . . . . . . . .. 65.8 105.7 94.1 89.03 92.4 21.95 3.33 155.4 37717 . . . . . . . . . . . . . . . . .. 63.0 117.0 105.1 89.83 101.1 21.60 2.67 147.2 37718 . . . . . . . . . . . . . . . . .. 67.0 99.3 87 8 88.42 83.2 21.72 1.71 138.9 37719 . . . . . . . . . . . . . . . . .. 60.0 105.2 97.0 92.21 94.4 21.88 2.68 148.9 37720 . . . . . . . . . . . . . . . . .. 64.5 111.4 96.6 86.71 94.8 21.40 3.33 152.3 37721 . . . . . . . . . . . . . . . . .. 66.5 117.7 103.0 87.51 100.1 21.58 2.73 147.7 Average . . . . . . . . . . . . . . . . .. 64.9 108.6 96.5 88.90 . . . . . . .. 21.73 2.76 148.9 Series 59 Preliminary 39222 . . . . . . . . . . . . . . . . .. 57.2 50.8 46.0 16.59 6.90 148.4 39223 . . . . . . . . . . . . . . . . .. 54.0 47.7 43.7 16.39 7.29 160.9 39224 . . . . . . . . . . . . . . . . .. 50.2 44.7 41.5 17.57 7.22 167.0 39225 . . . . . . . . . . . . . . . . .. 52.2 46.5 42.5 17.27 5.40 148.2 Average . . . . . . . . . . . . . . . .. 53.4 47.4 . . . . . . .. 16.96 6.70 156.1 Calories per 100 grams . . . . 138.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Full feed 52.0 479.1 442.2 92.30 432.3 21.25 11.17 224.7 49.9 411.2 383.0 93.14 374.7 22.43 7.97 201.5 54.9 500.1 464.2 92.82 451.6 22.55 10.59 226.7 51.2 550.1 507.8 92.31 495.0 22.02 7.55 195.2 53.5 529.5 485.5 91.69 470.0 22.49 6.60 189.0 58.0 574.2 544.2 94.78 527.6 21.52 9.20 208.6 52.7 504.2 468.2 92.86 455.5 22.59 7.80 200.8 55.3 534.5 495.5 92.70 482.8 21.82 9.21 209.6 56.9 531.0 491.7 92.60 477.8 22.41 10.40 224.1 51.8 463.3 430.0 92.81 421.0 21.90 10.09 218.3 53.6 507.7 471.2 92 80 . . . . . . .. 22.10 9.07 209.8 Limited feed ~ 39382 . . . . . . . . . . . . . . . . .. 52.5 199.7 183.2 91.74 178.3 22.50 4.00 164.8 39383 . . . . . . . . . . . . . . . . .. 50.0 204.2 189.5 92.80 180.7 23.03 2.57 154.4 39384 . . . . . . . . . . . . . . . . .. 54.4 188.5 176.2 93.47 170.0 23.13 3.20 160.8 39385 . . . . . . . . . . . . . . . . .. 51.3 212.0 193.7 91.37 187.4 24.22 3.10 166.1 39386 . . . . . . . . . . . . . . . . .. 53.6 187.0 170.1 90.96 164.3 23.21 2.40 153.8 39387 . . . . . . . . . . . . . . . . .. 53.6 183.7 172.5 93.90 167.6 23 .53 2 68 158.2 ‘Omitted from average. 02422 66H63H 059778326 190514621 ..... 890464004 239409890 T3L28 59H8LH 652061690 642051009 HHHHH 89 702383 0LT5049.3 45755 56 .56. 887900889 466744585 . . . .. 74 900112 6986898 8 t . . \ . n \ H H 6 H 0 5 9 mm .2522 m 5%. 55520235. 52552255.... 5.3%. 533583 53.12.92.555 FM 22422 67 .67 . 875899888 244623284 6767 . 8H9676898 255246564 p u t H H U mm 44305 68 .84 . 881044041 558914844 6884 . 918852828 218197706 We 11412.1 9.7. H7.8 H 9.6.4.11467.0 2366913167. 97.7.8. H 8916882418 152413832. 0r 23333 57 .66 . 891000990 110910190 5766 . 324335333 444444344 EN. 22222 11 .11 . 112222112 222122212 1111 . 222222222 222222222 . . U .. U H H H H Mum“. . 85.32 . 32 .5 . . 001570.45 . 515020.05. . 3.25. . 65.0.0.0.2.02 . 91305555 . Qtwbm 3442. 98.5.. 28666114. 8727916. 9 5.. 82932862. 43686816H 6M e108 8765 . 34 .3 . . 72254303 . 8888888 . 3 3 . . 40812770 . 35393049 . W W. 1111 U U U U 11111121 U U .. U 880778w7 U 9044904443 . t . . U nYtet 53448 71H85H 316874940 610265215 7185. 295811965 316335494 wm@m@ 60262 19.17. 381090058 425874556 1912. 797720336 311363549 .1 .1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . e e 34372 08 .30.. 012323442 778466348 0830 . 6555 654 3 30 0 uqumwrmw 99989 98 .99 . 999999999 888888.998 9899 . 9999 999 7%%99mm%9 WMM. 72185 35H6HH 525501609 578518529 35fiHH 054515556 555655551 Dkem 81188 10.9.. 720125 24 600513919 10 .. 771403654 6622921 4 metg 88757 45 .3 . . 733653 45 899899898 45 . . 721370133 46.53426 4 EWa 111111 . . U 111111211 O08777|Ovn78 344444444 5mm. 000505155 5554.5. 11.00.50.554 555505407 V86 842058561 5 286 62369.0.2 2.T.6...6 Ufltm 900000990 4 444 06460fl7m7 7B0%9MM%8 Wa 11111 1 1 987789H78 455444544 emwmm H H H H u 255252550 588027228 V8. 69191764 .HHHH 24231486. 4408387. Urwwamg 44545453 . . . . . 44555453 4554453 E BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STAT1ON Series and Laboratory number 16 Table 6-—continued. Composition, weights and calories per 100 grams for individua chickens. . . . . . . . .. H .m ......... ......... . . . . . . . .. .. .8 .....H.HH HHHHHHHHH . . . . . . . . . . . .r . . . . . . . . . . . . . . . . . . H H H H H H H H H H H E H H H . . . . . . . . . . . . . . . . . . . . . . .. .. 0 ...HHHHHH HHHHHHHHH . . . . . . . . . . . m . . . . . . . . . . . . . . . . . . . . . . 1d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Iléfluuunuuun yI ruu..u...nw........u . . . . . . . . . r. . . 8 . . . . . . . .6 . . . . . . . . . . . . . . . . . . 0% . . pd . . H H H H H H .1 H H H H .. H H .. . 2 4567 6 7 06 9 8 fi4%4444@Wg 1i2%3E%%%%%%W%%%gMmW%M%%M%g t55555555a 6m444aflf8oo888888at88888888a m99999999fl Sfi999HUn99999999fli99999999H 1 . 133333333V ..&m-..w.333vau33333333ym33333333v L A M ACF AL A S THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS 17 The calories per gram of chicken were calculated from the analyses by multiplying the grams of protein by 5.66 and the grams of ether extract by 9.35. This method of calculation was checked on 15 samples of dried chickens by comparing the calories calculated with those found by use of the Emerson adiabatic oxygen bomb calorimeter (Table 7). All the figures given are averages of two or more determinations. Table 7 shows that on an average the calculated values are only one per cent lower than the values actually found by means of the calorimeter. On account of the small quantity of material used in the calorimeter and the much larger quantities used in the chemical analyses, we consider the method of calculating the calories from the analyses to be more accurate than the direct calorimetric determinations. Table 7. Heat of combustion of dried chicken calculated from analyses and found by com- bustion in calories per gram. Analysis Heat of Combustion Diflcrence between Laboratory number Protein Fat Calculated Found calculaled per cent per cent Cal/gm. CaL/gm. and found 34005 . . . . . . . . . . . . . . . . . . . . . . .. 61.52 21 72 5.51 5.59 U8 34006 . . . . . . . . . . . . . . . . . . . . . . .. 56.26 26 97 5.71 5 83 12 34009 . . . . . . . . . . . . . . . . . . . . . . .. 59.59 25 16 5.73 5 85 12 34010 . . . . . . . . . . . . . . . . . . . . . . .. 62.27 20 93 5.48 5 63 15 34011 . . . . . . . . . . . . . . . . . . . . . . .. 61. 3 2O 66 5.43 5 48 1m 34012 . . . . . . . . . . . . . . . . . . . . . . .. 69.59 12 19 5.08 5 23 .15 34013 . . . . . . . . . . . . . . . . . . . . . . .. 66.33 14 87 5.14 5 30 .16 36176 . . . . . . . . . . . . . . . . . . . . . . .. 59.91 23 32 5.57 5 51 —».06 37410 . . . . . . . . . . . . . . . . . . . . . . .. 50.77 33 51 6.01 6 11 10 37411 . . . . . . . . . . . . . . . . . . . . . . .. 58.51 26 74 5.81 5 83 .02 37413 . . . . . . . . . . . . . . . . . . . . . . .. 55.61 29 71 5.92 5 94 .02 37412 . . . . . . . . . . . . . . . . . . . . . . .. 55.48 30 58 6.00 5 95 -—-.05 37414 . . . . . . . . . . . . . . . . . . . . . . .. 56.42 29 36 5.94 5 93 1 —.O1 37415 . . . . . . . . . . . . . . . . . . . . . . .. 66.90 14 60 5.15 5 19 .04 37416 . . . . . . . . . . . . . . . . . . . . . . .. 65.26 15 81 5.17 5 16 —.O1 Average (15) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5.58 ’ 64 06 ~The chickens were weighed weekly. The average weight may be taken to be the average of the first and last weighings, or it may be taken to be the average for each period. These two methods are compared, the first being termed “Average of first and last” weights and the second “Average weight by periods.” The average weight for each week is the weight at the beginning and at the end of the week divided by two. If the weekly weighings for 3 weeks are designated by the letters a, b, c, d, the average weight for the first week would be a + b, for the second, 2 b + c, and for the third, c + d. The average for the three weeks would be 2 2 a + 2b + 2c + d, and not a + b + c + d. The average weights by 6 4 periods are calculated by this procedure. The surface area was calculated for each weight of each chicken by the formula of Southgate (27), S:9.3W2/3. The average surface by periods is calculated in the same Way as the average weight by periods. 18 BULLETIN 'NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION Variations in the Composition of the Chickens As seen in Table 6, there are some differences in the rate of growth and the composition of the chickens fed on the same feed at the same time. There are also ‘some differences in the composition of the chickens killed at the beginning of the experiment. Such variations are to be expected. A summary of the differences in composition of the chickens is given in Tables 8 and 9. The differences between the live weights of some of the chickens at the end of the same experiment are grater than is desirable, even though the chickens used were selected from a larger group. These differences are probably due to variation in the growth intensity due to the heredity of the animals and cannot be avoided. Some differences occur with the percentage of protein, but the differences in this respect between individual chickens of the same lot are comparatively small. Table 8. Variations in energy content (calories) and live weights of chicks. Calories per 100 grams Live weight at end-grams Series Number Standard Standard Maximum Minimum Average Maximum Minimum Average deviation error grams grams grams Preliminary 55 179.4 148.4 162.2 13.043 6.521 53.4 45.4 49.6 . 156.4 163.6 6.234 3.117 51.5 43.7 47.4 175.0 180.1 6.369 3.185 56.5 50.8 53.8 186.6 186.8 .149 .086 68.5 64.2 66.2 148.2 156.1 9.346 4.673 57.2 50.2 53.4 146.8 163.8 12.173 3.850 126.7 106.3 117.2 148.8 157.9 6.084 1.924 119.8 100.2 110.4 150.5 159.0 4.889 1.546 205.5 139.1 167.6 138.9 148.9 5.870 1.856 117.7 96.5 108.6 147.0 158.2 7.506 2.374 212.0 181.2 193.4 205 .3 222 .5 10.293 3 .255 240.7 162 .7 204.7 194.1 207.7 9.405 2.974 235.2 166.7 195.2 195.7 220.3 15.561 4.921 534.0 375.5 438.4 184.1 202.8 9.908 3.133 243.2 163.0 210.7 189.0 209.8 13.249 4.190 574.2 411.2 507.7 ‘Excluded from average. The greatest differences between the individual chickens in the same group are found in the fat content. The differences are greater with the chickens fed on limited feed than with those fed on full feed or with the preliminary chickens. For example, the fat content of chickens on limited feed ranges from 2.53 to 6.13 per cent in Series 61, 1.53 to 3.57. per cent in Series 58, and 2.68 to 8.02 per cent in Series 60. For those on full feed, the range was from 6.60 to 11.17 per cent in Series 59, 6.90 to 11.73 in Series 53 and 5.85 to 10.16 per cent in Series 52. Evi- dently there are considerable differences in the ability of individual chickens to store fat. While there are appreciable differences in calorie content (Table 8) between the chickens in the same group, these differences are not as THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS 19 wide as might be expected from the variations in fat content. The protein is usually 10w when the fat is- high, thus tending to reduce the diiference in calories. A variation of 2% from an average of 20% protein is not as great a percentage variation as a variation of 2% on 8% of fat. The percentage of protein is thus relatively constant. In many groups the differences between the maximum and minimum calorie con- tent are less than 15 per cent of the average, and in some groups the Table 9. Variations in protein and fat content of chicks. Protein Fat Series Number Max- Min- Aver- Standard Standard Max- Min- Aver- Standard Standard imum imum age devia- error imum imum age devia- error % % % tion % % % tion Preliminary 55 . . . . . . . . . .. 17.80 16 25 17.19 .66 .33 8.41 6.03 6.94 1.07 .53 56 . . . . . . . . . .. 17.57 15 44 16.63 .89 .44 8.28 6.85 7.43 .61 .30 57 . . . . . . . . .. 17.97 16 79 17.38 .58 .29 9.37 8 44 8.74 .44 .22 58 . . . . . . . . . .. 18.72 18 23 18.50 .21 .10 11.10 8 65 9.32 1.18 59 59 . . . . . . . . . .. 17.57 16 39 16.96 .56 .28 7.29 5 40 6.70 .89 44 Limited feed 55 . . . . . . . . . .. 21.38 20.40 20.95 .36 11 7.27 3.08 4.84 1.42 .45 56 . . . . . . . . . .. 2110 20.47 21.13 .54 17 5.26 2.80 4 10 .88 .28 57 . . . . . . . . . .. 23.55 22.06 22.58 .48 15 4.08 2.47 3.34 .51 .16 58 . . . . . . . . . .. 22.15 21.40 21.73 .27 08 3.57 1.53 2.76 .71 .22 59 . . . . . . . . . .. 24 22 22.14 3.15 .56 18 4 15 2.23 2.90 .70 .22 Full feed 55 . . . . . . . . . .. 21 43 19 46 20.54 .64 20 13 58 9 3 11.37 1.27 40 56 . . . . . . . . . .. 22 39 19 74 20.78 .73 23 10 94 8 24 9.63 .99 31 57 . . . . . . . . . .. 23 60 21 56 22.58 .72 23 12 77 7 48 9.89 1.81 57 58 . . . . . . . . .. 23 84 20 02 21.10 1.06 34 10 26 6 64 8.91 1.35 43 59 . . . . . . . .. 22 59 21 25 22.10 .47 15 11 17 6 60 9.07 1.52 48 differences are only about 10 per cent. There are a few other groups, however, in which the differences between the maximum and minimum calories are more than 15 per cent. In Series 61, in which the chickens were on full feed 84 or 85 days, the calories range from 197.4 to 278.7 per 100 grams, a difference of over 40 per cent. It is unfortunate that chickens vary so much, but this variation is natural and cannot be pre- vented at the present time. Basis for Method of Calculating Distribution of Energy Between Maintenance and Productive Purposes The productive energy of feed eaten by the chickens was used partly for maintenance and partly for gain. In order to calculate the productive energy of the feed, it is necessary to ascertain the distribution of the feed between maintenance requirements and gain. The maintenance requirements should be related to the basal metabolism. The basal metab- olism of animals is generally considered to be in proportion to their surface area, or an exponential function of their weight. Mitchell et al. (24) state that “It is a matter of considerable significance that, for the cockerels and pullets, the basal heat production per square meter of body 20 BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION surface was remarkably constant for all age groups, except the youngest cockerels, while the basal heat production per kilogram of body weight decreased continuously with ‘advancing age. This fact constitutes a formidable argument in favor of the body surface as a unit of reference for basal metabolism as opposed to the body weight.” Whether the maintenance requirements are likewise in proportion to the body weight or to the surface is a question not yet decided, though it is frequently assumed that the latter is the case, as was done by Southgate (27) in experiments similar to these here reported. Mitchell and Hamilton (23) (p. 514), however, found that estimates of the maintenance requirements for swine were more satisfactory by the weight ratio than by the surface ratio, since by the surface ratio the maintenance requirements per 100 pounds of older pigs were greater than those for younger pigs, the opposite of what might reasonably be expected. As it was not possible to tell in advance whether the surface ratio or the weight ratio should be used in calculating the maintenance requirements of the chicks used in this work, both methods were tried. Preliminary calculations of the productive energy from the average results were made by an algebraic method similar to that of Southgate (27) in which no assumptions were made regarding the productive energy of the feed consumed. These preliminary calculations were made from the average data in Tables 10 and 11. The chief assumption is that the maintenance requirements vary according to the weight or to the surface area for both lots in each experiment. " The equations used were (1) WM-l-GIFX; (2) VM+H:DX. In these equations, W equals weight or surface of chick on limited feed; V is weight or surface of chick, full feed; G is gain of energy in calories, limited feed; _ H is gain of energy in calories, full feed; F is feed eaten, limited feed; D is feed eaten, full feed; . M is maintenance requirements for the period of the experiment per unit of weight or surface, in calories, and X is productive energy of the feed in calories. Solving for X and M: X: XG—WH M:FX—G or DX—H VF—~WD W V The maintenance requirements per day (N) would be M/K, if K is the number of days of the experiment. The productive energy values in calories per gram of the feed mixtures, as calculated by use of the above equations, with use of the weight basis and of the surface basis, are given in Table 14. We must here point out again that the chickens in each experiment were fed the same feed for the same period of time under the same conditions, the only difference being in the quantities of feed fed the two lots. THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS 21 The data in Table 12 show that the productive energy calculated by the Weight basis for maintenance is much higher than that calculated by the surface basis. The average productive energy for the 10 experiments calculated on the weight basis is 1.80 calories per gram of feed, while on the surface basis it is 1.33, a difference of 0.47 calories per gram. The difference is 26 per cent of the productive energy calculated on the weight basis. Table 10. Summary of data from feeding tests, chicks on limited feed. Average Average Average Average Feed Days weight by of first surface of first Gain of Feed Series Number Mix. of periods and last by and last energy eaten No. Exp. gm. weights periods surfaces cal. gm. gm. cm- cm. 14 21 77.7 83.5 168.2 175.3 107.2 152.4 14 21 81.4 90.2 173.3 184.2 87.7 163.7 22 21 75.9 84.5 165.0 175.8 97 0 164.7 22 21 71.7 79.5 158.9 168.4 83.3 165.7 23 21 83.6 86.8 177.1 180.9 36.0 167.6 24 21 69.9 74.9 156.6 162.5 72.3 171.0 18 42 114.9 119.7 216.3 215.3 215.6 460.3 18 42 122.0 136.0 225.9 238.5 181.2 476 8 23 42 104.4 110.2 203.6 206.5 163.6 430.8 24 42 112.1 123.3 211.9 221.1 208.9 488.7 25 84.5 214.2 268.5 318.8 348.8 723.3 1560.7 Table 11. Summary of data from feeding tests, chicks on full feed. Average Average Average Average Feed Days weight by oi first surface of first Gain of Feed Series Number Mix. of periods and last by and last energy eaten No. Exp. gm. weights perio surfaces cal. gm. gm. cm. cm. 14 21 108 0 109.9 207.4 206.7 256 4 272 1 14 21 112.6 122 8 211.2 222.2 249 2 307 7 22 21 121.8 128 3 223.8 225.8 351 9 361 5 22 21 114.0 121 6 214 2 217.7 309 7 360 9 23 21 136.3 137 9 242.6 239.7 297 5 411 4 24 21 99.8 107 4 196 2 201.5 225 2 316 8 18 42 168.9 195 5 274 6 288.8 583 3 849 9 18 42 198.7 208 4 309.6 307.6 595 9 933 2 23 42 212.9 245 5 319.6 333.3 808 2 1120 9 24 42 242.0 280.7 347.4 361.8 913.7 1291.0 25 84.5 400.5 460.2 478.6 484.9 1730.6 3066.8 An examination of the data in Table 12 shows that the productive energy calculated by the surface basis averaged 1.42 calories per gram when the period of experiment was 21 days, 1.21 calories per gram when the experiment was 42 days, and 0.89 calories per gram when the experi- ment lasted 84.5 days. Thus widely different values of the productive value of practically the same feed were secured when the surface basis for maintenance was used in the calculations. The surface basis in this respect is not a satisfactory basis for calculation of the productive energy. Similar data secured by the weight basis of calculating maintenance are much more concordant. The average calories of productive energy per 22 BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION gram of the feed for the chickens on experiment 21 days is 1.77, nearly the same as 1.85, the figure for those on experiment 42 days. The value for the single 84.5 day experiment is much higher, being 2.54 calories per gram, but not nearly so different from the others as the correspond- ing value secured from this experiment by use of the surface basis for maintenance. The weight basis for figuring maintenance gives practically the same productive energy for the same feed when the chicks were fed 21 days and 42 days, while the surface basis gives an appreciably lower value for the same feed when the chicks were fed 42 days. The weight basis therefore seems to give more reasonable results in the calculations than the surface basis. Table 12. Preliminary comparison of productive energy of feed and maintenance requirements of chicks calculated by the weight basis and by the surface basis. Productive energy calories per gram, calculated by Maintenance requirements Series No. Number Average and days on Feed of chicks weight of _ Energy Weight Surface experiment Mix. No. per lot chicks gm. Weight Surface production basis, basis, basis area coefficients calories per calories per basis (corrected) kilogram sq. meter per day per day 21 days 50 14 4 77.7 1.78 1.48 1.49 101 340 51 . . . . . .. 14 4 81.4 1.57 1.31 1.49 99 350 55. . . 22 10 75.9 2 .02 1.60 1.50 148 480 56 . . . . . . . 22 10 71.7 1.82 1.44 1.50 145 470 58 . . . . . . . 23 10 83.6 1.73 1.37 1 51 145 520 60 . . . . . .. 24 8 67.7 1.68 1.31 1.46 146 460 Average (6).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1.77 1.42 1.49 131 440 42 days 52 . . . . . .. 18 4 114.9 1.54 1.17 1.45 102 340 53 . . . . . .. 18 4 122.0 1.92 1.24 1 45 143 430 57. . 23 10 104.4 1.96 1 .24 1. 51 155 430 59 . . . . . . . 24 10 112. 1.96 1.17 1.46 159 410 Average (4). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.85 1.21 1.47 140 400 84.5 days 61 25 8 . . . . . . . . .. 2.54 .89 1 46 179 250 Average (ex- cept 61) (10) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.80 1.33 1 48 134 423 There are appreciable differences in the productive energy of the same mixture measured by different individual experiments, for example 1.78 in Exp. 50 and 1.57 in Exp. 51 for mixture 14. As will be shown later, these differences are, in part, caused by the method of calculation, since the algebraic method of calculation tends to increase the effect of small differences. The higher average value for productive energy of the mixture obtained by use of the weight basis for calculating maintenance, 1.80 calories per gram, is in better accord with the productive value of 2.83 calories per gram for corn,_ obtained by Mitchell and Haines (22) in respiration experi- ments with hens, than the lower average value of 1.33 calories per gram calculated by the surface basis. These higher values secured on the weight basis are also in better accord than the lower values secured on the surface basis with the net energy values of 1.98 to 3.55 calories per THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS 23 gram of dry matter secured with various foods by Forbes, Swift, and Black (10) on experiments with rats. The higher value obtained on the Weight basis is also in better accord with the productive energy of 1.8 calories per gram for a mixture of dried whole milk and ground oats, calculated by Southgate (27) from experiments with fattening chickens similar to those described. The above considerations indicate clearly that the weight basis for calculating maintenance is more nearly correct than the surface basis for the purposes of this work, when the results for the productive energy of the mixtures are considered. We next need to consider the maintenance requirements as secured by use of the surface basis and the weight basis. The maintenance require- ments corresponding to the productive energy values just discussed and calculated by the method already described, are given in Table 12. These values are not exactly correct, since the algebraic method of calculation gives different productive energy values to the same feed when used in different tests, but corrections for this will be made later. The maintenance requirements are here discussed in order to ascertain whether the weight basis or the surface basis should be used in calculating the maintenance requirements of the chicks and the productive energy of the feeds in the work here reported. From the data in Table 12, it is seen that the average maintenance requirements of the 6 sets of chicks fed 21 days, calculated on the weight basis, are 131 calories of productive energy per kilogram for chicks weighing 69.9 to 83.6 grams. The average for the 4 sets on experiment for 42 days with average weights of from 104.4 to 122.0 gm is 140 calories per kilogram. These averages differ only 7 per cent. The average maintenance requirement calculated on the surface basis is 440 calories per square meter per day for the 21 day experiment and 400 calories for the 42 day experiment. Table 13. Basal heat production of chickens, from Mitchell, et al (22). Heat produced daily Number of birds Age Weight Per ki10- Per square gram body meter body weight surface Days Gm. Cals. Cal's. Chicks: 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 t0 6 33 146 575 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 25 169 669 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-17 31 207 832 Cockerels: 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 283 166 1 ,441 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 683 96 8 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 1 ,324 81 864 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 1 ,928 71 859 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 2,705 63 864 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 ,728 62 856 These results may be compared with the basal heat production, reported by Mitchell et al. (20), part of which is given in Table 13. We must 24 BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION remember that our results in Table 12 are in terms of calories of pro- ductive energy of the feed, while those of Mitchell are in terms of calories of total energy of the body material. The average of 423 calories of productive energy per kilogram per day for maintenance found by the surface basis of calculation can be compared with the much higher value of 830 calories of basal metabolism obtained by Mitchell or 778 calories for mature hens reported by others (8). The 134 calories per kilogram (Table 12), found by the weight basis, can be compared with about 166 calories by Mitchell (Table 13) for small chicks or the 120 calories of basal metabolism per kilogram reported by Barrot and others (3) for Rhode Island Red chickens weighing 100 grams and being 20 days old. The average of 134 calories of productive energy per kilogram is equal to 74.4 grams per day of the feed mixture, which may be compared with the maintenance requirement of 42 grams of feed per day per kilogram as calculated from the results reported by Titus (28) for laying White Leghorn pullets, or the 46.5 gm per 1000 gm calculated from work of Brody, Fork, and Kempster (6) for laying hens. The pullets could be expected to have a lower maintenance requirement than the young chickens, as can be seen by the work of Mitchell in Table 13, already cited. The quantity of feed used for maintenance is in accord with what could be expected from previous work. Here again the calculations on the weight basis are more nearly in accord with previously recorded data than are those on the surface basis. Table 14. Maintenance requirements per day per kilogram of weight. Productive energy Calories Efiective Effective Metab- Feed by _ by Total organic digestible olizable Series Number Mix. by first and individual feed constit- nutrients energy No. periods last chicks, grams uents grams Calories weights weights by grams periods 50 . . . . . . . . . . . . . . . . . 14 102 95 103 57.0 49.4 37.5 _ 154 51 . . . . . . . . . . . . . . . . . 14 121 109 122 67.5 58.5 44.4 182 55 . . . . . . . . . . . . . . . . . 22 127 114 128 70.1 59.4 46.4 190 56 . . . . . . . . . . . . . . . .. 22 145 131 145 79.7 67.6 52.8 217 58 . . . . . . . . . . . . . . . . . 23 154 148 154 84.4 71.6 56.1 230 60 . . . . . . . . . . . . . . . . . 24 157 147 157 88 .5 72.6 55.6 228 Average (6) . . . . . . . . . . . . . . . . . . 135 124 135 74.5 63 .2 48 8 200 52 . . . . . . . . . . . . . . . .. 18 122 117 123 70.0 59.8 45.4 186 53 . . . . . . . . . . . . . . . . . 18 128 115 128 72.9 62.3 47.2 194 57 . . . . . . . . . . . . . . . . . 23 143 135 144 78.4 66 5 52.1 214 59 . . . . . . . . . . . . . . . . . 24 137 125 137 78.5 64.4 49.3 202 Average (4) . . . . . . . . . . . . . . . .. 133 123 133 75.0 63.3 48.5 199 61 . . . . . . . . . . . . . . . . . 25 113 90 113 63 9 53.9 42.5 174 Average except 61 (10) . . . . . . . . . . . . . . . . . . . . . 134 124 134 74. 8 63 .3 48.7 200 In the attempt to separate the quantity of food used for maintenance from that used for growth, it has been necessary to assume that the maintenance requirements vary in proportion to the surface (a function of the weight) or in direct proportion to the weight. It is possible that the maintenance requirements of the chicks on restricted food intake THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS 25 are lower than the maintenance requirements of the chicks on full feed or that the quantity of feed fed affects its digestibility and utilization, but we have at present no method of testing this possibility. It is also possible that the maintenance requirements of the chickens on experiment for 42 days are lower than those for the 21 days experiment. However, neither the average maintenance requirements by the Weight basis nor the surface basis indicate such a difference, and at present we can think of no other method of testing this possibility. The correction for differ- ences in body weight may introduce errors, but ‘such correction cannot be avoided in Work of the kind here presented. Everything considered, use of the weight basis for calculating the productive energy of feeds and maintenance requirements of chicks from our experiments gives more consistent results and results much more nearly in accord with our present knowledge than use of the surface basis. For this reason, in subsequent discussion the weight basis alone will be used. If better methods of calculation are discovered, this work can be recalculated, since the data are given. It is a peculiar fact that while the basal metabolism of chickens is more nearly in proportion to the calculated surface area (24) than to the weight, on the other hand maintenance requirements seem to be more nearly in proportion to the weight than to the calculated surface area. It is also peculiar that the maintenance requirements, in terms of pro- ductive energy, do not appear to be widely different from the basal metabolism, although somewhat lower. Calculation of Corrected Maintenance Requirements from the Data Having decided that the weight basis of calculation gives the more probable values for productive energy, we will now confine the discussion of the productive energy and maintenance requirements to the results found by this method of calculation. As previously shown, different energy values are secured for the same feed when the algebraic method is used, so that the preliminary calcula- tions of maintenance requirements need correction so as to use the same productive energy for the same feed. The productive energy values of the mixtures calculated from the production coefficients given for chickens in Texas Bulletin 372, as given in Table 12 of this bulletin, are on an average 21 per cent lower than the values secured in the work here pre- sented, when allowance was made for the difference in digestibility. The productive energy of the mixtures calculated from the production coeffi- cients, as given in Table 12, were multiplied by 1.21 to give the corrected values now to be used in the final calculations, and these are given in Table 17, as calories per gram calculated by corrected energy production coefficients. Another method of calculating the productive energy of the mixtures to be used in the final calculations is from the effective digestible nutrients. From the total percentage of effective digestible nutrients given in Table 4 and the productive energy found by the weight by period basis (Table 26 BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION 12), the average productive energy of one gram of effective digestible nutrients was calculated to be 2.76 calories per gram (N0. 61 excluded). The corrected productive energy was calculated for the different mix- tures by multiplying their content of effective digestible nutrients (energy) by 2.76. The average productive energy of the mixtures (1.76) so cal- culated Was about .03 calories lower than the values secured by the use of production coefficients already referred to (1.79), which differences did not appear to be large enough to require recalculation of the calculations already made with the use of the slightly higher values secured by the use of the production coefficients. These corrected values given in Table 17 were used to calculate the energy maintenance requirements and the corrected productive energy, the calculations being based on the average data given in Tables 1O and 11 and the data for the individual chicks. The method of calculation is different from the algebraic method used in the preliminary work. (See Table 15 for examples.) The total gain in energy (calories) of the chicks on limited feed (Table 10) is divided by the corrected productive energy in calories per gram of the feed eaten (Table 17). The dividend is the grams of feed required for the gain, and when this is subtracted from the total feed eaten, the difference is the feed used for maintenance during the experiment. This quantity of feed divided by the average weight of the chicken gives the grams of feed required for maintenance of one gram of chicken for the period of the experiment. The average weight of the chicks on full feed (Table 11) is multiplied by the grams of feed required for maintenance of 1 gram of chicken, and the product is the feed used for maintenance by the chicks on full feed. The total feed less the maintenance requirements is the quantity of feed available for gain, and the calories of gain divided by this figure gives productive energy of the feed in calories per gram of feed. This is the desired productive energy of the feed. See Table 18 for examples. The grams of feed required for maintenance of 1 gram of chicken, divided by the number of days of the experiment, gives the feed require- ment per day. This multiplied by the productive energy of the feed and by 1000, gives the maintenance requirements per kilogram per day in terms of calories of productive energy of the feed. Corrected Maintenance Requirements The maintenance requirements as calculated from the data are pre- sented in several forms in Table 14. The productive energy in calories was calculated (a) from the average data in Tables 11 and 12, with weights by periods, (b) from average data and the average of the first and last weights of the chicks, and (c) by individual chicks (Table 15) and the averages of the individual calculations. When (a) the average weights by periods were used, the results were more uniform than (b) when first and last weights were used; so the use of the average weight by periods is better. The maintenance requirements calculated from the average data (a) are identical with the averages (c) of the calculations 27- THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS ¢¢.-.-.-n 00-01-000! curl-cunt! ¢--¢.-.- nu--nfio%a 00.0: 00v 55.0.5 00.NN: 0.00 0.00: 0.av 0.00: 0.00 N.0v .........:§m 00.N: 0a.0 @035 0N0: a.av :40: v.0a 0:: 0 00 a.0v .. Itloamvm $5 00.0 NWO: a0.aa 0.v0 0.00: 0.NN: 0:0: 0.a0 :.a0 .........a00v0 0a.: N:.v $.12: 03:0: :00 0.00: 0.0: 0.vv: 1% v.v0 ........000v0 0a.: 0N.0 vNNv: 0a.0N: 0am 0.00: v.:v N.:0: 0.av N.0v .........v00v0 2.: 0T0 a0.aN: 00.00: N00 N.v0: a0: 0N0: 0~v0 0.00 .........000v0 00.0: 00v 00.00: 00.55 0.00. v.00: 0.00 0.2; 0.00 0.0v .........000v0 00.: 00.v 00.03 00.0: 0.00 0N0: v.N0 0.00: v vv a.0v ........$mvm 0v.N: 2x0 v0.0: a0.0: 0.00 0.2: 0N0: 0.0: :.Nv 0.vv .........000v0 8.2 m0 0 v0.0: 00.00: N.v0 v.v0: 0.NN: a.NON 0.00 0.av .........m00v0 NN 000m 00 00500 .- ¢ p». --||¢-.- ¢---=- -@-o|u-n n~u.nuu%¢% 00.0: 00v a0.N:0 53m :5 00$ 0.5: 0.0aN 0 00: N.v: ..0vN00 070: N0.v N005 v0.0v0 N00 0.5:. v.0: v.:0N 0.0: a.a: .........vvN00 a0.N: 0N.v NN.N00 0N.0v0 N0: 0.50. véoN a.N:m NA: 0.0: .........0vN00 QNN: 00.v Nv.0aN 0N.:v0 N00: 0.vv¢ a.00: 0.5.0 0.0: 0.0: .........mvN00 . 0: 08m 00 @0500 00-» --- nvu u 0 o Ilbiul 00: o~o|n-|- nnn-cnu%q& NvN: vN.v 00.000 N:.N00 0.0N: v.Nv0 0.:N N.0vN N.v0 0.0: .........0a000 N00: v0.v aaANO 00.50 0.5: 0.2% 00v: a.v0N v.a0 a.v0: .........va000 3.2 :0 0v.v0N N:.N:0 0N0: 0.000 v.00N 0.000 a.a0 7:: .........0a00m 2N: 0a.0 0v.NaN 0a.000 a.v: 0.000 m.00N :5 0.0v :0: .........ma00m 0: 000m N0 @0500 IIIQI u ~ uc- -¢ - Inocnill Icnnlntoa n-n-¢¢-%¢& 00.: aa.0 N00: av.00: 0.00 N00: 0.00 a.v0: 0.00 50v .........0av00 00.: $0 0N0: v0.0: 0.00 adv: 0N0: 0.2: véa v.00 ....a0v00 00.0: 00v 00.00: :00: 0.00 0.2: 0.N0 0.0: a.0a 0.00 00v00 2.: :N.0 N000: 00.0: 0.00 N.a0: 0.N0 0.av: 0.va N.v0 .. ......v0v00 3 08m J0 @0060 Qulnlvunu n: Danna. occnolucll n-ouo-n - ->u-a-u%v% 00.: 00.0 vNNm: 00.N0: 0.00 0.00: N.0a v.0: 0N0 v.vv ..........NNv00 $5 00.0 00.vN: 000a 0.00 0.00: 0.0a it; 0.av 00v ..:Nv00 00.0: 00.0 N0.0N: a0.0a 0N0 a.v0: N.N: v.Na: 0.00 v.vv ..........0Nv00 0N.0 $4. 000a aa.0v 0.00 0.0: ENN: a.00N 0.00 a.av ........a:v00 w: 08m 00 000000 .50 .50 .50 .50 00: 505 00: 505 00: .65 .50 00500 .50 .30 400 000 .50 >00 $5 >00 50m 02:5 50m 130m. 005050 0o 50000 005050 0.53500 0500500 002.500 002200 050103500 000m 0o 500G 000050 00505.0 > E0003 5 005050 . 00.010 005E R35: 0 050>< 0050005»: 0050500505 .52 000m 6500-050 1500205. .50 0000-50-00 0050505150.. 005050552 .0: 0.000. 28 BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION . ....> . . . . . . . . . . . . . .. . . . . . . . . ...-.w...... .-....-.-.-A¢§Q Q@N.MQ>< :h.w: ww.w mm ow: wh :w: w mm w.wh: w.:w :.mw: w o:: w.ww . .:Nhhw www: hw w aw w: hwow: w :N w m: o.ow :.hw: :.ho: h.ww ..............omhhw :w.w: mw w :: 2: wwww: w wm o ww: w.ww w.ww: h.ww h.ow ..............m:hhw hmw: ww w ww ww: wwhw: w w w ww: h.o: o.ww: w.::: :.@h ..............w:hhw mww: hw h w: ww: wwww: w hm N. wh: :.ow h.ww: wwo: w.ww ..............h:hhw wmw: ah h hw ww: wwww: mom o hw: w.ww w.ww: wwo: w.ww .. . . ......w:hhw www: ww m aw ww: wmzww: ww o ww: w.w wow: o.m:: h.wh ......w:hhw hw.w: :w w ww wh: ww.ww: o.ww w ww: o.ww w.ww: Q8: w.:w . ..w:hhw ow.w: :w w oh wh: omww: ww: h wh: w.ww w.hw: ww:: w.ww . ...........m:hhw www: ww h ohww: wwww: :.hm w uh: w.ww mhw: who: w.hw .. ..........m:hhw mm :59: .ww mzbm h -u-n- 0 ¢ . - - . - .>-a¢u-¢ 1-4 n-n-n uqa-:.n%o?& ww.w: No w hwwww :h.www w wo: o www wow: owhm w.ww o.wo: ..............:..wwhw m:.w: :h h mm wmw mwwww w mm h wmw :2: wwwm w.ww w.ww: ..............wwwhw 3.2 wmh wh wow wwhww : 5 w wmw h.ww: w.:w w.ww w.o:: ..............hwwhw mww: mm h mm how No.:ww : ww: : www wwwm w.ww w.:w o.w:: .. Ziwwwhw oww: :w h w: wmw wo www : wh N wow w.ww: w w:m h.ww w :o: . wwwhw N:.w: mh h o:.wmw oo.:ww w wm a www w.wh: o hwm w :w w.ww: . . . Iwwwhw wow: wm w aw www :w.wmw w ww o www ww:: o ha: w.ow o.ww . . . . . . .. wwwhw wow: 2a wwwww owwww w wh o wmw w.ww: w mmm w.hw w oo: . .. . . Nwwhw wo w: hw.h owfimw h:.www a wo : :ww w.wh: w mwm w.ww N o:: . .. .......:wwhw ww w: www omwww wwhww w.oh o wow h.ww: mafia h.ww w.ww ..............owwhw Ea». mm :59: .hw masw . n---~. 0 - - . . - - - h - --¢uo n - Isl-O .-.-uv~o--@o%% w: w: www Nhww: mowm: m.:w o oh: w.wh w aw: : ww w.ww ..............o:..whw $ w: mwh hmhw: 8.2: w.ww : ow: h.ww h ww: o wh w.wh ..............wwwhw w: w: hh h h:.ww: ww.w:: h.ww w ww: w.ww w ww: w wh o.:h . . . wwwhw ow w: No w hwww: :w.wm: w.ww w :h: w.ww w :w: o hh w.wh . . Zhwwhw ow w: ww w wwhh: 3am: w.hw w ow: w.ww h.ww: w :h w.ww . .. . Iwwwhw mm w: on w :N.Nh: 2am: whw m ww: w.ww w ww: o hh w.oh . . wwwhw mo w: w:.h :w.ow: wowo: w.ww m ww: w.ww m oh: : :h w.wh wwwhw ww w: wh w wwww: hwow: w.hw m ww: w.ww h ww: N mh N.:h wwwhw wmw: ww h owww: ww.h:: w.ww N hw: h.ww w.ww: o hw h.:h .............mmwwhw oo w: w: h :o.ow: :h.ho: o.ww h :w: w.ww : ww: w ww w.:h :.wwhw mm woon: ww wasw 8cm ém éw éw oo: 5.: oo: 5Q oo: 5Q 4mm 85% 4cm :5 .13 .13 4mm >3 5:: >2. 5n: v2.5a 5n: :w:c.:. >326 :0 c525 >955 @355 i538 wuoivm moiimo 355335 uvvm: we Emmy >955. >525 h :56; c: >355 :53: 125: RUE: o w5>< ozwuswob: oucwcvfiawfi 5w :55»: ionntzanvlmnoxfiau Euoviws: 5.: wofiiaoiu munoEohi-vou ounanofliuw»: w: o_nn,:. 29 THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS . . ........ . . . ..-. ..-.Awv UwNH®>< fir: Ea mwdB mwmm: 2Q mmvmH 50E. mmmm ma...“ P2: ambH $5 3...? mmmm: .\..@3. o...,wm_ >5? mmnm m mm mmmm nmmmm 2.: 3a mmmmm 8mm: ca? 0.52 mmmh mmmw 9E $4.5m ...H..@mw@m 2 I Ra mhmmm mhmw: ms? 0.3x: 9w? mmow m E Alma mmmmm 8Q mmm 8am»... Chimm wmmm msvfi fifia i2... Wm» m 2N . . . wmmmm ~54: mam mmmom $.82 ommw mflwmfi 2E mdmm m om m.omm . Iimmwmm 8.2 Ram wHsMa. wflfi: H83. n55“ Nflmmm mmmw 9% mmmm . mmmmm Qflfi 2:. $.26 mwmm: a mhm mafia :5. ommm :6 N53 . 4.23m mm wwvm .5 35w -.- ... . . ... .-<.... ..1..... m.mmmm..m-.-a%w mvmflhmw>< 2.3 0M3.“ $1.3 3.4;: in. M22 mm: m 9: m om m mm . .. Iimvmmm 2&2 8a $42: @592 5mm 2x: mmm wefi mmm wmw . zzwfiam $4.; mmm 3.9: 5.9.: 0mm 3.2 #2 3w»; m mm mmm . . 5.2m 2.2 mam $.22 31$; 5mm m6: Q3 6N2 was wmh . . . . “v2.3 3.2 2.0 mama wmmmfi 6:. mm: 9Q. W8; Wm» 9% . . . . mvmmm SE2 .85 $4.2 22.3: m2. mm: “ME. 55$ ma» mfmm 3a....“ amfi i; .33: mowfl W? wA: my? $5.3 fin» 9E . mwmmm mmmfi mom 2.9: mmdmm mmm mmmfi mmm w wfi fi mm o am Iimwmam wm wmsm .2 35w . - - . - . n - - . - - -¢. .-.<-.u -»i--4 3E wmm modmm 3.5m 0mm “Qt. mA: m 3N 50h m >2 . .. 1.3m?“ M32 i: mmdmm mwsfi... Q2: n48. wmflm mmmm P2. .m~mo~ .. .. . ......ommmm 3.2 £5 3.6mm ofiwwm ma: imam mmom mmhhm dflmh. bk: mmmmm 3.2 9:. vommm mwgwm Aim: ~52. Ywi w Rm 0.2. m m: . . . .....mwmmm Q92 mmB vmmmm Cimmm mm: Q05. .22: omhm m i. 2W2 . . . . . . . swmam 3.3 3w mmmmm oommm ~82 oafi. mun: mlmm mmfi. 062 . . mwmmm wwfi was awe?” owmmm mm: 9Q... mbmm hQmm 7Q m Hmfi . . Illmwmmm 3Y2 2: mmAmm Ewswm mm: wafi. o.mcm Fmww w? N9: . . . vmmmm 8.: 5w wmmmm momhm 9R" mmom m.mmm wmmm mbm m}: 3.2 2: Zmmm Sam». $52 95a. w mmm m 8m w N... w o2 . mmmmm fim vfii m... 82$ 4cm 6cm Em Aim oofi 5n o2 3Q o2 SQ Aiw v2.8» gum .13 .13 . .13 4mm >3. 5Q >3. pom v2.5a Em 730M. $65 mo cofiwo >m~o=o Hcomcoo ucomcoo 2.26m @2813 . Eoiwznvo uovh mo c120 >326 ~mNh®CO > Qswww? E %w.~®fi0 vwoh 12th $31G o 39/4 ofidoswopm wocmcottwfi pom wowh JuQS-Cwiénvimiwlumiu ESUTZHZC uQw “$125073 QeGOEQuI-vwu oonaaoizss .5 v35. 30 BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION for individual chicks in 5 experiments, and differ less than 1 per cent from the other six. The laborious calculation by individuals gives prac- tically the same results as the easier method of using the average data. The grams of total feed used for maintenance are given in Table 14 and are average values for individual chicks. The average figure of 74.8 gms is higher than the 42 gms from data of Titus (28) and 46.5 from calculations of Brody et al. (6) for laying hens. However, young growing chicks can be expected to have higher maintenance requirements than laying hens. The effective organic nutrients required for maintenance also are given in Table 14. The term “effective organic nutrient” is used to specify the sum of the protein, the fat multiplied by 2.25, and the nitrogen-free extract. The term “effective organic constituents” is used to distinguish it from the total organic constituents, which would include crude fiber also. The effective digestible nutrients required for maintenance are also given in Table 14. The term “effective digestible nutrients” is used to signify the digestible protein plus the digestible fat multiplied by 2.25 and plus the digestible nitrogen-free extract. The digestible crude fiber is not included, and the term “effective digestible nutrients” is used to distinguish it from the total digestible nutrients, which include the crude fiber. Metabolizable energy requirements for the maintenance are also given in Table 14.. Since direct determinations of metabolizable energy were not made, the metabolizable energy was calculated on the assumption that the effective digestible constituents have a metabolizable energy of 4.1 calories per gram, which is Rubner’s figure as quoted by Armsby (1). This is naturally only an estimate, which will be corrected by work now in progress. The average metabolizable energy of 200 is higher than the basal metabolism of 166 for chicks of approximately the same size as reported by Mitchell (22). The wide differences in the maintenance requirements calculated from some of the experiments require discussion. Variations are shown in Table 16. In Experiment 50 (Table 14), the maintenance requirement is 102, while in Experiment 6O it is 157 calories per day per kilogram, a difference of nearly 50 per cent. There are no corresponding differences in the productive energy calculated from the data of these experiments, since in Experiment 50 the productive energy is 1.79 calories per gram and in Experiment 60 it is 1.72. The productive energy is calculated from data from chickens on limited feed and corresponding chickens on full feed. Since there is little difference in the productive energy, the factors which caused a high maintenance requirement in Experiment 60 and a low maintenance requirement in Experiment 50 must have affected the chickens on full feed and those on limited feed in the particular experi- ment in a similar way. Therefore the average differences in maintenance requirements between the two experiments were due to environmental conditions, which affected both lots of chickens in the same way. Possibly THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS 31 the temperature of the room in which the chickens were kept was lower, part of the time, in one experiment than in the other. Table 16. Average maintenance requirements in productive energy, calories per kilogram per day, calculated from individual chickens, with standard deviation and standard error. Maintenance requirements, Series Feed Number calories per kilogram Standard Standard Number No. 0f deviation error chickens Average Maximum Minimum 21 days 5 . . . . . .. 14 4 102 6 113.4 82.6 13.7 6.9 51 . . . . . .. 14 4 1215 131.5 111.7 8.9 4.4 55 22 10 127 6 149.3 109.7 11.3 3.6 56 . . . . . .. 22 10 145 1 161.8 130.0 11.1 3.5 58 . . . . . .. 23 10 154 4 169.8 142.6 8.5 2.7 60 . . . . . .. 24 8 156 7 164.1 141 3 7.2 2.5 Average (6) . . . . . . .. 8 134 7 148.3 119 7 10.1 3.9 42 days 5 . . . . . .. 18 4 122 5 134 2 107 4 11.4 5.7 53 . . . . . .. 18 127 6 131 6 122 4 4.2 2.1 57 . . . . . .. 23 10 143 5 154 3 133 2 7.0 2.2 59 . . . . . .. 24 10 137 4 149 8 126 8 6.6 2.1 Average (4) . . . . . . .. 7 132 8 142 5 122 5 7.3 3.0 84 5 days 61 . . . . . .. 25 8 113.1 123.7 103.0 8.4 3.0 Average (all) (11) . . . . . . . . . . . . .. 7 132.0 144.0 119.1 8.9 3.5 In the different experiments, there was more variation in the average maintenance requirements of the chickens fed for 21 days than in the requirements of those fed for 42 days. It appears possible that younger chickens may be more sensitive to environment than the older ones. The kind and amount of feathers may have something to do with this. The maintenance requirements were calculated for each individual chick on limited feed, as detailed in Table 15. The results are summarized in Table 16. There are some wide differences in the average maintenance require- ments between the several experiments. The standard deviation is greater with the younger chickens than with the older ones. The average standard deviation is 10.1 for the younger chicks and 7.3 for those on experiment 42 days. The standard error is quite low. The standard error, as could be expected, is lower where 10 chicks were used per lot, than where only 4 were used. It is evident that individual chickens differ appreciably in their power to use the energy of food. Consideration of these data leads to the conclusion that the use of only a few individuals may give incorrect results. The basal metabolism varies considerably, even on the same individual, as shown by Barott et al. (3). Corrected Productive Energy The corrected productive energy of the mixtures is given in several terms in Table 17. The productive energy of the mixture, in calories per 32 BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION gram, was calculated from (a) the average data in Tables 13 and 14, using average weights by periods, (b) the same data using averages of the first and last Weights, (c) individual chicks records in Table 18, the averages being given in Table 17, and (d) from the corrected energy production coefficients. When the average weights per period were used, the results were more uniform than when the averages of the first and last weight were used, showing that the use of weights by periods is better. The productive energy calculated from the average data is only slightly different from the average by individual chickens, indicating that the shorter method might be as good as the longer method. The effective organic constituents have an average productive energy of 2.14 calories per gram. The efiective digestible nutrients have an average value of 2.73 calories per gram for the chickens on 21 days experiment and 2.84 for chickens on 42 days, with an average of 2.78 calories per gram for all experiments. It appears that these averages could be used in calculating the productive energy of feeds similar to these used in this experiment; but the fact that the digestible nutrients of one kind of feed may have a different productive energy from those of another kind of feed must not be forgotten in connection with such calculations. They can be used for preliminary calculations, until differ- ences in different kinds of feed have been ascertained by experimental work. The calories of productive energy are on an average 67.6 per cent of the estimated metabolizable energy, or one calorie of productive energy requires 1.48 calories of metabolizable energy. The average productive energy calculated from the energy production coefficients given in Bulletin 372 is 1.48. If we use the productive energy of 1.80, the results secured are 122% of the assumed values used in Bulletin 372. The mixture used consists of 51% of yellow corn meal, 19% wheat gray shorts, 10% dried buttermilk, 6% cottonseed meal, 4% tankage, 2% bone meal, 2% oyster shell, and 1% salt. On an average, the factors for productive energy of the feeds used. in the mixture, as given in Texas Bulletin 372, should be multiplied by 1.22 to bring them in accord with the results secured; but it is possible that the individual feeds require to be multiplied by figures a little higher or lower than 1.22. This can be ascertained only by further comparison of the relative productive energy of the different feeds which enter into the mixture. Application of the correction to the energy coefficients given in Bulletin 372 will be delayed until more information is- available regarding the productive energy of the individual feeds. The productive energy of the mixture here reported gives abasis for estimating the productive energy of chicken feeds more accurately than has previously been the case. The differences in the corrected productive energy given in Table 17 are not as great between the different experiments as in the preliminary 33 THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS $5. $4 Ra 3a $4 $4 2Q 2.4 . . . . . . . . . . . . . . 13C 3 “Qvoxo 2w. we omw$>< wflw $4 wvm 2d Nwé 9: a: . . . . . . . . . .. . . . . . .. 1.35 ___VJQ%SQ>< 06m Q; 5N 3N 3A wm fi 2: R; mm . . . . . I5 was. mew N? Q4 3g 3N i: S; $4 NBA . . . . . . .. . . . . 2A3 owm$>< o i. £4 ~55 mwem 2w; 8a £4 RA X . . . . . . . . . . . 1mm “.2 $4 8a 3N m: 3N 2: £4 mm . . . . . . . . 1B 9% 3N4 3a hfim mm: £4 Q: E; M: 4 . . . . . . . . . . 1mm Yaw a: 8a QmA ma; ma; 2; m»; wfi . ...m@ 3% Nw 9% B; m§~ :.N 2.4 m»; w»; 5A . . . . . . . . . . ISV omw$>< m? $4 §.N 8a 2.4 m»; N»; Rkfi fi . . . . . . . :8 m3 £4 3N 8a wh; $4 m“; mm: mm . . . . . . . . . . . Iwm Q5 $4 Ema 24.. Q: E4 $4 Nwé mm . . . . . . . . . . . 1mm NAN. 3A NQN wWN Q: £4 Q: Q: mm . .. . . . . 1mm m? ma; 8a Q: EA mm: £4 2: 3 . . . . . . . . . . . I5 :5 on; flaw wow a: Em“ a»; 2: El . . . . . . . :8 n52. S hmuocv 82w .6.» EmLm 3Q H623 “on ficfiofiooo >505 ofiaoswoha wuiofio wwioiwo Bammo? mEmMQB GOUQSUOuQ ‘Enmwsonmwofi Ho oioEo dfinzbsc dwcwsfigwnoo dxoEo $2 mwoion >925 dZ Ho i6“. SQ E 2.5 .5“ Bfifiwmflw 06%.. iwswr/smz: wcw 3E wn wofioioo .52 @215 YE woiom mtwfioofio 5 o>fioobw 5 3 >5 3 wooh uobfldg >526 “XQNNSOQQQQE @2530 ENQM MQQ $1.513 ~U0®w _NwOw Gm uofla-iflmo Gama MO an: dEovrfi-fl oifiumvumw ofiuooho 05a .M .26..» Q-fiflflm-Ofidavi fiuo-Smifloo OmGNUhQ Q>SUPUQ 05w 6.00.“ fiNeOu 0-: M9 MNhQEQ oiwonflofm .2 ~52. 34 BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION values for productive energy given in Table 14. This is probably due partly to the method of calculation, since the algebraic method used for the results in Table 14 may magnify small diiferences in the data. The productive energy was likewise calculated for ‘each individual chicken by use of the average maintenance requirements from Table 14, and the data for each chick on full feed in the corresponding experiment. The details are given in Table 18 and the results summarized in Table 19. These are also compared in Table 17. The standard deviation averages .18 calories for chicks 21 days on experiment and .26 for chicks 42 days on experiment. The standard error averages .07 calories for chicks 21 days on experiment and 0.10 for chicks 42 days on experiment. Table 18. Productive energy of feeds calculated for individual chickens Average g Feed Feed Prod. weight Initial Final Gain of Feed for above energy Laboratory by energy energy energy, eaten, main- main- of feed, Number periods, content, content, cal. gm. tenance, tenance, cal/gm. gm. cal. \ cal. gm. gm. Series 5O 35715 . . . . .. 92.0 75.3 288.7 213 5 234.9 110.1 124.8 1.71 35716 . . . . .. 113.4 86.0 375.6 289 5 277.1 135.7 141.4 2.05 35717 . . . . .. 101.4 79.3 290.8 211 5 246.3 121 4 124.9 1.69 35718 . . . . .. 125.2 90.5 401.7 311 2 330.1 149.9 180.3 1.73 Average (4) . . . . 108.0 . . . . . . . . . . . . . . . . 256 4 272 1 . . . . . . . . . . . . . . . . 1‘. 79 Series 51 35771 . . . . .. 98 5 84.4 308.3 223 9 263 8 139 6 124 2 1.80 35772 . . . . .. 121 7 98.6 344.7 246 0 351 5 172 5 179 0 1.37 35773 . . . . .. 112 8 88.7 369.9 281.3 316 7 159 9 156 9 1.79 35774 . . . . .. 117 2 102.3 347.9 245.6 298 6 166 1 132 5 1.85 Average (4) . . . . . . . . . . . . . . . . . . . . . . . . . . .. 249.2 307 7 . . . . . . . . . . . . . . .. 1.71 Series 52 36083 . . . . .. 181.3 72.1 722.7 650 6 879.3 533.9 345.5 1.88 36084 . . . . .. 162.6 69.9 655.1 585 1 814.8 478 8 336.0 1.74 36085 . . . . .. 178.7 64.8 712.2 647 4 894.7 526 2 368.5 1.76 36086 . . . . .. 153.1 65.2 515.1 449 9 810.8 450 8 360.0 1.25 Average (4). . . . . . . . . . . . . . . . . . . . . . . . . . . . 583 3 849.9 . . . . . . . . . . . . . . . . 1.66 Series 53 ' 36262 . . . . .. 202 7 120.3 743 5 623 2 915 6 620.6 295 0 2.11 36264 . . . . .. 198 7 103.9 719 2 615 3 969 6 608.3 361 3 1.70 36265 . . . . .. 200 6 117.8 562 5 444 7 858 0 614.2 243 8 1.82 36266 . . . . .. 192 9 107.5 808 1 700 6 989 6 590.6 399.0 1.76 Average (4). . . . . . . . . . . . . . . . . . . . . . . . . . . . 595 9 933 2 . . . . . . . . . . . . . . . . 1.85 Series 55 372 . . . . .. 120.2 80.9 373.4 292 5 336.8 176 9 155 9 1.88 37373 . . . . .. 128.9 73.6 496.1 422 5 381.8 189 7 192 1 2.20 37374 . . . . .. 128.4 77.4 413.8 336 3 374.2 189 0 185 2 1.82 37375 . . . . .. 138.0 83.8 493.0 409 3 385.0 203 1 181 9 2.25 37376 . . . . .. 110.8 67.5 404.0 336 5 337.9 163 1 174 8 1.92 37377 . . . . .. 139.0 79.6 490.0 410 4 411.9 204 6 207 3 1.98 37378 . . . . .. 106.2 61.1 348.1 287 0 319.2 156 3 162 9 1.76 37379 . . . . .. 8.8 59.1 376.7 317 7 322.0 145 4 176 6 1.80 37380 . . . . .. 126.2 78.6 457.9 379 4 398.7 185 8 212 9 1.78 37381 . . . . .. 121.9 81.0 408.0 327 0 351.0 179 4 171 6 1.91 Average (10).... 121.8 . . . . . . . . . . . . . . .. 351 9 361.5 . . . . . . . . . . . . . . .. 1.93 Series 56 37471 . . . . .. 106 0 66.4 356.9 290.6 318.0 177.5 140.5 2.07 37472 . . . . .. 104 9 66.2 377.3 311.1 351.7 175.7 176.0 1.77 37473 . . . . .. 130 2 76.0 443 3 367.4 417.5 218.1 199.5 1.84 37474 . . . . .. 121 8 72.9 399 2 326.3 365.0 204.0 161.0 2.03 37475 . . . . .. 114 1 78.0 317 7 239.6 334.4 191.1 143.3 1.67 37476 . . . . .. 121 7 71.1 437 8 366.7 379.7 203.8 175.9 2.08 37477 . . . . .. 102 0 67.0 340 6 273.7 338.9 170.8 168.1 1.63 37478 . . . . .. 105 8 75.2 333 5 258.3 334.3 177.2 157.1 1.64 THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS 35 Table 18. Productive energy of feeds calculated for individual chickens—-—Continued Average _ _ _ _ Feed Feed Prod. weight Initial Final Gain of Feed for above energy Laboratory by energy energy energy, eaten, main- main- of feed, Number periods, content, content, cal. gm. tenance tenance caL/gm. gm. cal cal. gm. gm. Series 56——-Cont. 37479 . . . . .. 118.7 73.0 394.9 321.9 392.8 198.8 194.0 1.66 37480 . . . . .. 115.1 62.4 403 8 341.4 376.9 192.8 184.1 1.85 Average (10).... 114.0 . . . . . . . . . . . . . . .. 309.7 360.9 . . . . . . . . . . . . . . .. 1.82 Series 57 . 37620 . . . . .. 227.7 82.6 940.8 858.2 1118.8 749.7 369.1 2.33 37621 . . . . . . 184.1 84.2 850.8 766.6 1026.9 606.2 420.7 1 .82 37622 . . . . .. 213.3 87.3 804.2 716.9 1086.2 702.3 383.9 1.87 37623 . . . . .. 215.6 85.7 1037.7 952.1 1250.0 709.9 540.1 1.76 37624 . . . . .. 211.3 91.3 874.8 783.5 1110.6 705.6 405.0 1.93 37625 . . . . .. 195.4 84.7 737.5 652.9 1032 .0 643 .4 388.6 1 .68 37626 . . . . .. 187.5 79.8 813.1 733.3 982.8 617.4 365.4 2.01 37627 . . . . .. 237.4 80.8 1118.7 1037.9 1248.0 781.7 466.3 2.23 37628 . . . . .. 225.3 88.2 771.9 683.7 1168.2 741.8 426.4 1.60 37629 . . . . . . 228.4 84.8 981.9 897.1 1185.1 752.0 433.1 2.07 Average (10). . .. 212.9 . . . . . . . . . . . . . . .. 808.2 1120.9 . . . . . . . . . . . . . . .. 1.93 Series 58 37702 . . . . .. 140.4 108.0 441.7 333 .7 430.7 248.7 182.0 1.83 37703 . . . . .. 140.2 113.3 451.0 337.7 428.6 248.4 180.2 1.87 37704 . . . . .. 126.8 103.8 399.0 295.1 371 .5 224.7 146.9 2.01 37705 . . . . .. 131.2 111.0 317.4 206.5 344.5 232.4 112.1 1.84 37706 . . . . .. 152.4 109.3 439.9 330.6 477.9 270.0 207.9 1.59 37707 . . . . .. 125.3 103.8 380.3 276.5 406.3 222.0 184.3 1 .50 37708 . . . . .. 148.1 113.8 492.0 378.2 466.7 262.4 204.3 1.85 37709 . . . . .. 132.0 102.8 412.3 309.5 387.6 233.9 153.7 2.01 37710 . . . . .. 133.3 106.3 313.8 207.5 365.7 236.2 129.5 1.60 37711 . . . . .. 133.6 110.5 410.2 299.7 434.3 236.7 197.6 1.52 Average (10).... 136.3 . . . . . . . . . . . . . . .. 297.5 411.4 . . . . . . . . . . . . . . .. 1.76 Series 59 39372 . . . . . . 235.7 72.1 993.7 921 .6 1120.9 777.2 343.7 2.68 39373 . . . . . . 202.7 69.2 771.6 702.5 1034.6 668.4 366.2 1 .92 39374 . . . . .. 245.2 76.1 1052.1 976.1 1319.5 808.5 511.0 1.91 39375 . . . . .. 257.9 71.0 991.3 920.4 1417.0 850.4 566.6 1.62 39376 . . . . .. 252.4 74.2 917.6 843.5 1322.7 832.2 490.5 1.72 39377 . . . . .. 271.0 80.4 1135.0 1054.7 1632.3 893.6 738.7 1.43 39378 . . . . .. 227.7 73.0 940.1 867.1 1268.8 750.8 518.0 1 .67 39379 . . . . . . 253.5 76.7 1038.6 962.0 1329.6 835.9 493.7 1 .95 39380 . . . . .. 253.2 78.9 1101.8 1022.9 1297.2 834.9 462.3 2.21 39381 . . . . . . 221.1 71 .8 938.7 866.9 1167.3 729.0 438.3 1.98 Average (10).... 242.0 . . . . . . . . . . . . . . .. 913.7 1291.0 . . . . . . . . . . . . . . .. 1 .91 Series 60 3953 . . . . . . 109.9 65.5 330.1 264.6 359.7 204.3 155.4 1.70 39535 . . . . .. 81.9 69.6 245.3 175.7 250.7 152.3 98.4 1.78 39536 . . . . .. 97.3 81.0 225.6 144.6 273.2 180.9 92.3 1.57 39537 . . . . .. 102.5 73.5 308.0 234.5 358.8 190.6 168.2 1.39 39538 . . . . .. 98.2 67.4 314.2 246.9 318.1 182.6 135.5 1.82 39539 . . . . .. 91.6 60.5 280.7 220.2 287.2 170.3 116.9 1.88 39540 . . . . .. 128.0 86.0 388.6 302.6 409.3 238.0 171.3 1.77 39541 . . . . . . 89.0 56.4 268.6 212.2 292.1 165 .5 126.6 1.68 Average (8)..... 99.8 . . . . . . . . . . . . . . .. 225.2 318.6 . . . . . . . . . . . . . . .. 1.70 Series 61 39823 . . . . .. 404.2 62.9 1918.2 1855.3 3070.5 2181.8 888.8 2.09 39824 . . . . . . 404.0 65.6 2068.0 2002.4 3068.0 2180.7 887 .3 2 .26 39825 . . . . . . 368.1 76.9 1614.8 1537.9 2899.0 1986.9 912.1 1.69 39826 . . . . . . 342.5 78.8 1450.1 1371.2 2548.0 1848.7 699 .3 1 .96 39827 . . . . . . 382.0 75.2 1546.3 1471.1 2940.0 2061.9 878.1 1 .68 39828 . . . . . . 446.4 64.8 1829.0 1764.2 3313.0 2409.5 903.5 1.95 39829 . . . . . . 508.6 85.4 2378.3 2292.9 3972.8 2745.3 1227 .5 1.87 39830 . . . . . . 343.1 53.5 1603.5 1550.1 2723.3 1852.0 871.4 1 .78 Average (8)..... 400.5 . . . . . . . . . . . . . . .. 1730.6 3066.8 . . . . . . . . . . . . . . .. 1.91 36 BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION There are some wide deviations between the maximum and minimum for the several experiments. Productive energy calculated from experi- ments on a few animals may thus deviate Widely from the average. Both the standard deviation and the standard error are comparatively lOW, indicating that the averages are substantially accurate, especially when 6 or more chickens were used in a group. Examination of the data shows, however, that there are individual chickens for which the productive energy deviates quite widely from the average. The maximum and minimum values are given in Table 19. In Series 55, the productive energy ranges from 1.76 to 2.25, with an average of 1.93. In Series 57 it ranges from 1.60 to 2.33, with an average of 1.93. It seems clear that experiments on a small number of animals might give too high or too low results, and that the results might be misleading. Evidently the individual chickens differ widely in their ability to utilize the energy of feed. Table 19. Average productive energy of feed calculated from individual chickens. Productive energy of feed Series Feed Number calories per gram Standard Standard Number No. o deviation error chicks Average Maximum Minimum 4 1.80 2.05 1 69 .17 08 4 1.71 1.85 1 37 .22 ll 10 1.93 2.25 1 76 .17 05 10 1.82 2.08 1 63 .18 06 10 1.76 2.01 1 50 .19 06 8 1.70 1.88 1 39 .16 06 8 1.79 2.02 1 56 .18 07 4 1.66 1.88 1 25 .28 14 4 1.85 2.11 1 70 .18 09 10 1.93 2.33 1 6O .23 07 59 10 1.91 2.68 1 43 .35 11 Average (4) . .. . . . . . . . . 7 1.84 2.25 1 50 .26 10 84.5 days 25 191 2.26 168 20 07 Average of all (11) . . . . . . . . . . . . .. 1 82 2 13 1.55 21 08 Average ex- cluding No. 61 . . . . . . . . . . . . . . . . 1.81 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Similar variations in the maintenance requirements have previously been pointed out. In calculating the productive energy, it has been necessary to use average maintenance values. It is possible that some individual chickens on the full feed had higher or lower maintenance requirements than the average used. This difference in maintenance requirements of the individuals, if it could be allowed for, might increase the differences in the productive energy calculated for the individual chickens, or it might decrease the differences and bring the productive energy values closer together. This is a question which requires further study. It is clear, however, that differences in the animals may result in different utilization of the feed by the individuals, so as to result in different productive energy, and that a sufficient number of animals must THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS 37 be used to equalize the individual differences and thereby secure an accurate average value. Utilization of the Ration for Maintenance and for Gain The utilization of the energy of the ration for maintenance and for gain should be of some interest. The quantities of feed calculated as used for maintenance by individual chicks are given in Tables 15 and 18 and are averaged and recalculated for use in Table 20. In the different experiments, the percentages of feed used for maintenance by chicks on limited feed ranges from 60.9 per cent in Experiment 50 to 88.2 in Experi- ment 58, With an average of 74.2 per cent. The corresponding figures for chicks on full feed range from 47.5 per cent in Experiment 50 to 70.4 in Experiment 61, with an average of 57.9 per cent used for main- tenance. The percentage used for gain by chicks on limited feed ranges from 11.8 in Experiment 58 to 39.9 in Experiment 50, with an average of 25.8. The percentage used for gain by chicks on full feed ranges from 29.6 to 52.5, with an average of 42.1. The chicks on experiment 21 days utilized larger proportions of the feed for gain than did those on experi- ment 42 days. Table 20. Utilization of the ration for energy of maintenance and of gain by chicks on limited feed and on full fee . Percentage Percentage Feed eaten per _ for maintenance for gain chick per day Series Feed _ and period No. Limited Limited Limited feed Full feed feed Full feed feed Full feed , gm. gm. 21 days 50..... 14 60 9 47.5 39.1 52.5 7.3 13.0 5l..... 14 70 3 51.8 29.7 48.2 7.8 14.7 55..... 22 67 7 49.6 32.3 50.4 7.8 17.2 56..... 22 724 52.9 27 6 47.1 7.9 17.2 58..... 23 88 2 58.7 11.8 41.3 8.0 19.6 60..... 24 76 1 58.3 23.9 41.7 8.1 15.2 Average (6) . . . . . . .. 72 6 53.1 27.4 46.9 7.8 16.2 42 days 5 18 73 3 58.5 26 7 41.5 11.0 20.2 53..... 18 78 3 65.2 21 7 34.8 11.4 22.2 57..... 23 79 2 62.5 20.8 37.5 10.3 26.7 59..... 24 75.6 61.8 24.4 38.2 11.6 30.7 Average (4) . . . . . . .. 76.6 62.0 23.4 38.0 11.1 25.0 84.5 days 61..... 25 73 8 70.4 26 2 29 6 18.5 36.3 Average (11) . . . . . . .. 74.2 57.9 25.8 42.1 10.0 21.2 Utilization of Protein This work was carried out to ascertain the productive energy of the feed, but since data regarding protein are available, they will be briefly discussed. The data give information regarding the utilization of protein by individual animals, but We will discuss the results only on the basis of the averages. Table 21 gives a summary of the average data. 38 BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION The grams of protein gained divided by the grams of digestible protein fed gives the percentage of the digestible protein stored in the animal, without allowing any protein for maintenance. The average percentages of digestible protein retained are given in Table 22. These averages are remarkably constant. The retention of digestible protein by the growing chicken is high. The protein stored by the chickens in percentage of the total protein fed is given in Table 22. The average percentage stored by the chickens on the 21 day experiment is 39.3 by those on limited feed and 42.5 by those on full feed, while for those fed 42 days, it is 35.1 for the chickens on limited feed and 38.1 for those on full feed. A little higher percentage is stored by the chickens on full feed than by those on limited feed. The percentage of the digestible protein stored averages 54.7 and 54.9 for 21 days feeding and 51.8 and 50.4 for 42 days feeding. Table 21. Average protein gained by chicks and eaten in feed. Protein in chicks Protein in feed Series Number Mix. No. At _ _ _ beginning At end Gain Total Digestible gm. gm. gm. gm. gm. Limited feed 2 days 0 . . . . . . . . . . . . . . .. 14 8 25 20.99 12.74 29 95 21 78 51 . . . . . . . . . . . . . . .. 14 9 29 22.36 13.07 32 17 23 39 55 . . . . . . . . . . . . . . .. 22 7 83 21.87 14.04 32 23 32 56 . . . . . . . . . . . . . . .. 22 7 28 20.71 13.43 32 20 23 47 58 . . . . . . . . . . . . . . . . 23 10 67 20.97 10.30 32 36 22 72 60 . . . . . . . . . . . . . . . . 24 7 38 18.65 11.27 32 06 21 95 Average (6) . . . . . . . . . . . . . . . . . .. 8 45 20.93 12.48 31 79 22 77 42 days 52 . . . . . . . . . . . . . . .. 18 7 18 39.65 32.47 85 98 59 76 53 . . . . . . . . . . . . . . .. 18 11 40.81 29.81 89 07 61 91 57 . . . . . . . . . . . . . . . . 23 8 21 35.27 27.06 83 19 58 42 59 . . . . . . . . . . . . . . .. 24 7 98 41.32 33.34 91 63 62 72 Average (4) . . . . . . . . . . . . . . . . . .. 8 59 39.26 30.67 87 47 60 70 84.5 days 61 . . . . . . . . . . . . . . .. 25 7 30 107 74 100.44 294 97 193 97 Full feed 21 days 50 . . . . . . . . . . . . . . .. 14 8 37 31 50 23.13 53 47 38 88 51 . . . . . . . . . . . . . . .. 14 9 46 33 98 24.52 60 46 43 97 55 . . . . . . . . . . . . . . . . 22 7 84 39 33 31.49 70 24 51 19 56 . . . . . . . . . . . . . . .. 22 7 20 38 05 30.85 70 12 51 10 58 . . . . . . . . . . . . . . .. 23 10 72 44 25 33.53 79 44 55 78 60 . . . . . . . . . . . . . . .. 24 7 30 31 00 23.70 59 40 4O 66 Average (6) . . . . . . . . . . . . . . . . . .. 8 48 36 35 27.87 65 52 46 93 42 days 52 . . . . . . . . . . . . . . .. 18 7 30 70 08 62 78 158 76 110 35 53 . . . . . . . . . . . . . . .. 18 11 04 71 65 60 61 174 32 121 17 57 . . . . . . . . . . . . . . .. 23 8 20 9 40 83 20 216 45 151 99 59 . . . . . . . . . . . . . . .. 24 8 O7 104 14 96 07 242 06 165 69 Average (4) . . . . . . . . . . . . . . . . . .. 8 65 84 32 75 67 197 90 137 30 84.5 days 61 . . . . . . . . . . . . . . .. 25 7 33 199 30 191.97 579 63 381 16 39 THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS R. hm. .2... 0m. mm. mm. 0.0m 0&0 00¢ mam . 122C 2m 2o omw~o>< 0m. mm 0m. mm. 2%.. 8.. :5 0.2m 2.2% 2.2%.. @922. mi” 0m. 0m 0m. 02A 0m. B. 0.2% 98 2.0m 2.3 . .. . . 12$ vmw$>< mm. 8 3. 0m. 0m. mm. 00m ma... 210m v.3 . . . .1329“. 2m. 0m. m? 2. 20. 0h. 2.4a 0.02. 2am 9mm . .. 2b mm 0m. £2 22$ m0. 0m. 0.0m N22“ we.“ 9mm . . . Zmn mm ma. w”. mm 2.. £2 0.0m ma... m? wan . . . . 22mm 25. Nv o ‘.1 - a o - -u.-.u¢~»¢ Ion .1 - p ¢ -vu n nun - 0 o u u n -o-u-|»u u-%wm “m. 3H 5. mm. 2m. 02$ mam hi“ 9Q. 0.0m 1.11.130 wma~o>< 0m. mm 02% 3. 0m. 00 mam m 2m 0 m». mam mm. mm E. ma. 02». 00. 2.00 m? N2. 0.2m 1.1223 2N. mm .8. $1 2m. 2.2% v.00 N22“. 0.2% 2.2. .. . . 20m mm. 02 mm. 0m. m? 0m. 0.20 N00 0.2% 05¢ . . . . 2mm mm. mm. 2%. mm 00. m2“. was 202...... 00¢ 20.0w .. .155 mm. 02. mm. 0m. Q. 0m. 9% m S ma? ma... .. . . . 210m mix. 3 268 2P2 2502 2026.2 2P2 253 2X62 22h 2.32 25o .62 228 .62 25o .62 26o $2 20232822 252E212 2.32512 .258 222,2 .253 62.2 2:2 .268 252822 2.32522 2033:0022 2.3332232 230.2. 2032222272 3Com 253w 002 .62 >2. .62 oocwnufinmE .52 2.32 E382 22am c2 22502 E3022 2.222832 5% E 2.552 c2322 2392. 620220 m: 5029,22 .20 2523x2223 .NN Q55. 40 BULLETIN NO. 5'71, TEXAS AGRICULTURAL EXPERIMENT STATION l The feed nitrogen retained by rats is given at an average of 17.9 to 18.8 per cent in one set of experiments (9) and 20.3 to 24.1 in another (4). The percentage of total protein stored by growing chickens (39 to 42) is much higher than the percentage stored by rats (17.9 to 24.1). How- ever, in experiments with growing rats, Forbes et al., (10) secured some- what higher figures for the retention of nitrogen, ranging from 23 to 41 per cent, but still lower than for the chickens. The productive value of the digestible protein was calculated by an algebraic method similar to that used for productive energy. The values for the productive value of the protein for the individual tests varied widely, being from .55 to .89. The average for the 6 experiments of 21 days was 0.71 and for the 4 experiments of 42 days was 0.73. These two averages have a high measure of agreement. The value of 0.73 was used to calculate the protein maintenance requirements and the productive protein value of digestible protein, in a similar way to that used for FX -— G, in which M _‘W__ is the maintenance requirement per gram of animal, for the entire period; F is the grams of digestible protein eaten; X is the productive coefficient for protein (0.73 here used); G is the grams of protein gained by the animal; and W is the average Weight (by periods). The maintenance requirement given in the table is for a day per 100 grams, which is 100 M divided by 21 days or 42 days. The protein used for maintenance per day per 100 grams of chicken is given in terms of productive protein, of digestible protein (productive protein divided by .73), and of total protein (digestible protein divided by coefficient of digestibility). There are considerable differences between the maintenance values calculated from the different experiments. The average values were 0.51 gm total protein per day per 100 grams for the chickens on full feed 21 days, 0.49 for those on limited feed, and 0.56 gm for the chickens on experi- ment 42 days full feed and 0.57 for those on limited feed. These values agree quite closely. Considerable work has been done on the biological values of proteins, although generally with percentages of protein lower than those used in practical feeding. As summarized by Boas Fixsen (7), the biological value of the proteins of cereals and seeds in a ration containing over 10% protein ranges from 57 to 71, legumes from 38 to 72, tankage at 74, and coconut at 58. This is an expression in percentages of the body nitrogen stored divided by the food nitrogen absorbed minus the metabolic nitrogen of feces and urine. The maximum of biological values is near the average of 73 for productive protein obtained in the work here reported, while the average of the biological values cited would be appreciably below this figure of 73. It appears probable that the protein of cereals may be utilized by animals to a larger extent than has been previously assumed from consideration of the biological values. productive energy. The equation used is M = THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS 41 SUMMARY Eleven experiments involving 256 chicks were made for the purpose of ascertaining the productive energy of a basal mixture of feed, in order to secure fundamental values which could be used as the basis of a system of productive energies of poultry feeds. Representative chicks were analyzed at the beginning of the test. One lot of chicks was fed individually all the mixture they would eat; the other lot was fed individually about half this quantity. All chickens were analyzed for protein and fat at the end of the test. Digestion experiments were made on the feed mixtures used with chicks of similar age. The gains in energy of the chicks, calculated from the protein and fat content of the chicks and the quantity of feed consumed, together with the length of the feeding period, gave data from which to calculate the maintenance requirements of the chicks and the productive energy of the feed. Individual chickens differ in their capacity to grow and to utilize feed. Appreciable variations were found in the weights and composition of the chicks fed the same feed for the same period of time, especially in the fat, which might vary from 2.53 to 6.13 per cent for chicks on limited feed, or from 6.60 to 11.17 per cent for chicks on full feed as between individual chickens in the same experiment. The energy content of the chicks did not vary as much as the fat. The difference between the maximum and minimum calorie content is only 10% of the average with some groups, and less than 15% with many of them. The maintenance requirements of the chicks and the productive energy of the feed were calculated in two ways, first on the assumption that the maintenance requirements vary according to the surface area, and second that they vary according to the weight. The maintenance requirements and the productive energy were lower when calculated on a surface basis than when calculated on the weight basis. The productive energy calculated on the surface basis was appreciably lower for the 42 days experiments than for the 21 days experiments, but when calculated on the weight basis, the results were almost the same for both these periods of experiment. Higher values for productive energy were secured when maintenance requirements were calculated on the weight basis than when calculated on the surface basis. These higher values ‘are much more nearly in accord with the results secured by other workers by means of respiration experiments on chicks fed corn and rats fed mixed feeds; and the weights of the feed required for maintenance are not out of line with work reported by others. ‘ The use of the average weights by periods gives more concordant results than the use of the mean of the initial and final weights of the chicks. The use of the average data gave practically the same results as the longer method of calculating from the data of individual chickens and averaging this data. The productive energy of the mixture was on an average 22% higher than the productive energy calculated from the factors previously given 42 BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION in Texas Bulletin 372. This value can be used to correct productive energy values of chicken feeds previously reported as soon as sufficient data on the relative productive energy of different kinds of feeds are available. The productive energy required for maintenance as calculated from these experiments is lower than the requirements of energy for basal metabolism of chickens, as found by other workers. However, the quantity of feed required for maintenance is higher per day per kilo- gram of Weight than the quantities‘ given by other workers for larger chickens. Appreciable differences in maintenance requirements, with no correspond- ing change in productive energy, were found between different experi- ments on practically the same feed mixtures. These differences in main- tenance requirements are ascribed to differences in environmental condi- tions affecting the chicks. ' While the basal metabolism of chickens as reported by other workers is more nearly in proportion to the calculated surface area than to the weight, the maintenance requirements, as found in the experiments here reported, are more nearly in proportion to the weight than to the surface area. p The maintenance requirements as found, average per day per kilogram, are 74.8 grams of total feed, 63.3 gm of effective organic constituents, 48.7 gm of effective digestible nutrients, 134 calories of productive energy, and 200 calories of metabolizable energy. The effective organic con- stituents are the sum of the protein, the ether extract X 2.25, and the nitrogen-free extract, as the ash, water, and crude fiber are not considered to furnish energy to chickens. The effective digestible nutrients are the sum of the digestible protein, digestible ether extract X 2.25, and digest- ible nitrogen-free extract. - The average, of the standard deviations for the productive energy of the feed mixtures is 0.21 on 1.82 calories of productive energy per gram, or about 11 per cent, while the average of the standard errors is 0.08, or about 5 per cent. If only a few chickens were used, the results secured might deviate appreciably from the actual value. The average maximum_ is 2.13 and the average minimum is 1.55 calories per gram, the difference being 0.58, or 27 per cent of the maximum. The productive energy averaged 1.79 calories per gram of the feed used. The productive energy of the effective organic constituents was 2.14 calories per gram, of the effective digestible nutrients 2.77 calories per gram; and 67.6 per cent of the calculated metabolizable energy, over maintenance‘, was used for productive purposes. The average maintenance requirement for chickens 28 to 50 days old is 132 calories of productive energy per kilogram live weight per day. The average of the standard deviations is 8.9, or about 7%; and the average of the standard error is 3.5, or about 3%. There is less variation in the average maintenance within the experiments than in the productive energy. On an average 25.8 per cent of the limited ration was used for gain in THE UTILIZATION OF THE ENERGY OF FEED BY GROWING CHICKENS 43 weight and 42.1 per cent of the full ration. The remainder was used for maintenance. As an average of all the 11 experiments, 40.0% of the total protein was stored in the chicks 0n full feed and 37.3% in those on limited feed. Of the digestible protein, 56.9% was stored in chicks on full feed and 52.9 in those on limited feed. If the productive value of the protein is calculated by a method similar to that used for productive energy, differences are found between the individual experiments, but the productive value of the digestible protein averages 0.71 for the 21 days period and 0.73 for 42 days. The productive value of the protein so calculated is higher than the usual biological value received for similar foods. It appears possible that the biological value of the protein of cereals is higher than it has been considered from previous work. Using the value 0.73 of the digestible protein for productive protein, the average productive protein required for maintenance was 0.27 gm per 100 gm a day for chicks on limited feed and on full feed. The maintenance re- quirements for digestible protein averaged 0.37 gm per day per 100 gm of chicks and the maintenance requirements for total protein averaged 0.53 per day per 100 gm. ACKNOWLEDGMENT The analytical work required for the work here reported was done by Ralph L. Schwartz, Cecil B. Pounders, S. E. Asbury, Mrs. Velma Graham, Mrs. Jean DeMottier, and other members of the staff. The thanks of the authors are also due to Prof. H. H. Mitchell of the Illinois Agricultural Experiment Station, Prof. F. B. Morrison of the New York (Cornell) Agricultural Experiment Station, Prof. G. E. Ritzman of the New Hampshire Agricultural Experiment Station, and Prof. Max Kriss of the Pennsylvania Experiment Station, all of whose valuable com- ments and suggestions on preliminary copies of the manuscript resulted in considerable changes that appear in the Bulletin here presented. v REFERENCES 1. Armsby, H. P. 1917. The Nutrition of Farm Animals. The Macmillan Company, New York. 2. Barott, H. G., Byerly, T. C., and Pringle, Emma M. 1936. Energy and gaseous metabolism of normal and deutectomized chicks between 10 hours and 100 hours of age. Jour. Nutrition. 11:191. 3. Barott, Herbert G., Fritz, James G., Pringle, Emma M. and Titus, Harry W. 1937. Heat production and gaseous metabolism of young male chickens. Jour. Nutri- tion. 15:145-167. 4. Black, Alex, Kahlenberg, Orme J., Bratzler, John W. and Forbes, E. B. 1937. The utilization of energy producing nutriment and protein as affected by deficiency of iron and copper. Jour. Nutrition. 14:521-533. 5. Braman, W. W., Black, A., Kahlenberg, O. J., Voris, L., Swift, R. W., and Forbes, E. B. 1935. The utilization of energy-producing nutriment and protein in white and yellow corn and in diets deficient in vitamins A, D, and G. J. Agr. Research. 50:1. 6. Brody, Samuel, Fork, E. M., and Kempster, H. L. 1938. Energetic efficiency of egg production and influence of live weight thereon. Research Bul. 278, Missouri Agr. Exp. Station, 59 pages. 7. Fixsen. Margaret A. Boas. 1935. The biological value of protein in nutrition. Nu- trition Abstracts & Reviews. 4:447-459. 8. Dukes. H. H. 1937. Studies on the energy metabolism of the hen. Jour. Nutrition. 14:341-353. 44 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. BULLETIN NO. 571, TEXAS AGRICULTURAL EXPERIMENT STATION Forbes, E. B. 1937. The effects of deficiency of phosphorus on the utilization of food energy and protein. Jour. Nutrition. 14:419-433. Forbes, E. B., Swift, R. W. and Black, Alex. 1937. The measurement of the efficiency of diets. New apparatus and procedures. Jour. Nutrition. 15:321-50. Fraps, G. S. 1925. Energy-production coefficients of American feeding stuifs for ruminants. Texas Agr. Exp. Sta. Bul. 329. Fraps, G. S. 1928. Digestibility and production coefficients of poultry feeds. Texas Agr. Exp. Sta. Bul. 372. Fraps, G. S. 1928. Supplementary energy-production coefiicients of American feeding stuffs fed ruminants. Texas Agr. Exp. Sta. Bul. 402. Fraps, G. S 1931. Productive energy of feeds calculated from feeding experiments with sheep Texas Agr. Exp. Sta. Bul. 436. Fraps, G. S 1932. The composition and utilization of Texas feeding stulfs. Texas Agr. Exp. Sta. Bul. 461. 63 pages. Fraps, G. S. 1937. Practical applications of productive energy values to problems con- cerningzfeeds and feeding. Proc. Am. Soc. An. Production, November 26-28, 1937, pp. 20- 6. Jones, J. M. and Stangel, W. L. 1938. Effect of calcium supplements on gains of lambs fed sorghum fodder or sorghum silage as the roughage portion of the fatten- ing ration. Texas Agr. Exp. Sta. Bul. 563, 47 pages. Kahlenberg, O. J., Black, A., and Forbes, E. B. 1937. The utilization of energy pro- ducing nutriment and protein as affected by sodium deficiency. Jour. Nutrition. 13:97-107. Kellner, O. 1905. Die Ernahrung des landwirtschaftlichen Nutztiere. Kleiber, Max, Goss, Harold, and Guilbert, Harold R. 1936. Phosphorus deficiency metabolism and food utilization in beef heifers. Jour. Nutrition. 12:121-153. Mitchell, H. H. 1937. The importance of the relations between energy, protein, and minerals in measuring the nutritive value of feeds and rations. Proc. Am. Soc. An. Production, November 26-28, 1937:2942. Mitchell, H. H. and Haines, W. T. 1927. The basal metabolism of mature chickens and the net energy value of corn. Jour. Agr. Res. 34:927. ’ Mitchell, H. H. and Hamilton, J. S. 1929. ‘Swine Type Studies. III. The energy and protein requirements of growing swine and the utilization of feed energy in growth. Ill. Agr. Exp. Sta. Bul. 323. Mitchell, H. H., Cord, L. L. and Haines, W. T. 1927. castration on the basal heat production of chickens. Jour. Agr. Res. 34:945. Mitchell, H. H. and Carman, G. G. 1926. Does the addition of sodium chloride in- crease the value of a corn ration for growing animals. Jour. Biol. Chem. 68:165-215. Morrison, F. B. 1936. Feeds and Feeding. Southgate, B. A. 1929. The maintenance requirement of the fattening cockerel with a note on a proposed new method for the determination of the surface area of The effect of age, sex, and birds. Jour. Agr. Science. 20:206-212. Titus, H. W. 1928. The gross maintenance requirement of white Leghorns. Poultry Science. 8 :80-84.