.A. B. CONNER, DIRECTOR, College Station, Texas BULLETIN NO. 663 _ -J.~‘ TEXAS AGRICULTURAL EXPERIMENTLIEIQAEION NOVEMBER, 1944 DIGESTIBILITY OF FEEDS AND HUMAN FOODS BY CHICKENS G. S. FRAPS Division 0f Chemistry AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS GIBB GILCHRIST, President E23-ll44-3M-L130 [Blank Page in Original Bulletin] A knowledge of the digestibility of feeds and foods is necessary in order to ascertain their feeding values. As part of a comprehensive investigation 0f the feeding values of various feeds and foods, a number of digestion experiments were made. This Bulletin presents a summary of 718 digestion experiments made with chickens. The feeds tested include chicken feeds, some human foods and some representa- tives of the nutrients contained in foods, such as albumen and casein to represent proteins, starch to represent carbohydrates and cotton- seed oil to represent fats. Average coefficients of digestibility are given, and also the standard deviations when 4 or more experiments were available for the same feed. The standard deviation gives infor- mation as to the variability of the digestion coefficients. The digest- ibility of the nutrients o-f an entire ration is less variable than the digestibility of the nutrients of corn meal when fed as 50 per cent of the ration. Some work on the determination of uric acid is reported. CONTENTS Page Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 Methods for Determining Uric Acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7 Texas Method for Uric Acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7 Ammonia Nitrogen in Chicken Feces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7 Studies of Other Methods for Correction for Uric Acid . . . . . . . . . . . . .. 7 Results» of Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8 Digestibility of the Feeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..10 Effect of Protein on Digestibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..16 Variations ofiDigestibility of Rations Compared With Digestibility Of the Chief Feed in the Ration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..18 Comparison of Mixtures and Rations . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..18 Discussion 0f Some Individual Feeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 References . . . , . . . . . . . . . . . . . . . . . . . . . . . . 0722 1i DIGESTIBILITY OF FEEDS AND HUMAN FOODS BY CHICKENS By G. S. Fraps Chief, Division of Chemistry The work here presented is a part of a comprehensive investigation of the values of the energy of different kinds of feeds. The nutritive values of feeds and foods depend to a great extent upon their digestibility. Only the nutrients which are digested can be utilized. The utilization of the digested nutrients for the production of fat and flesh by growing chickens and by rats has been discussed in other publications (6, '7, 8). A number of digestion experiments were made for the purpose of the work referred to above, and additional experiments were also made. The work on the utiliza- tion of energy showed that differences in the productive energy of various feeds are due to a greater extent to differences in their content of digestible nutrients than to differences in the energy values per unit of the digested nutrients. This makes a knowledge of the digestibility of feeds of high importance. A summary of 39 foreign experiments and 112 American experiments on the digestibility of poultry feeds was given in Texas Bulletin 372, in 1928 (4). The Bulletin here presented contains a summary of the results of an additional 718 digestion experiments made at this Experiment Sta- tion. A summary of 1'78 experiments made elsewhere with poultry not included in Bulletin 372, is given in addition. As previously shown (5) chickens have high digestive powers for sugars and starch, and low diges- tive powers for proteins and for nitrogen-free extract remaining when sugar and starch have been deducted. The feeds tested include chicken feeds, some human foods, and some representatives of the nutrients contained in foods, such as albumen and casein to represent proteins, starch, sugar to represent carbohydrates or nitrogen-free extract, and cottonseed oil to represent fats. Procedure A few of the experiments were made on single feeds fed alone, but most of them were made on feeds in balanced mixtures and in rations used for productive energy experiments, from which the digestibility of the chief feed was later calculated. The constituents of the rations used in the productive energy experiments have already been published (6, '7, 8). Bal- anced mixtures were prepared, to contain 2.5% calcium carbonate, 1.5% tricalcium phosphate, 1.0% salt and 0.2% cod liver oil concentrate. The balanced mixtures were made to about 18% protein with casein in the case -of low protein feeds, and diluted to the same protein content with corn 6 BULLETIN 663, TEXAS AGRICULTURAL EXPERIMENT STATION meal when high protein feeds were tested. A series of digestion experi- ments were made on mixtures of casein and corn meal so as to obtain their digestion coefiicients which were used in calculating the digestion coefii- cients of the other feeds with which they were used in balanced mixtures. The baby chicks used in many of the experiments were kept in elec- trically heated brooders at 92-94° F until they were about 4 weeks old. Older chickens were also used and were kept at room temperature. The chickens over 8 weeks of age were fed in wire metabolism cages, 24 by 24 by 18 inches made of 2 inch mesh chicken Wire on a galvanized iron frame, supported on legs over a galvanized iron pan. The floor of the cage was of % inch mesh chicken wire which was reinforced by heavy 3/16 inch wire running diagonally from corner to corner of the frame. The younger chicks were fed in groups of four to eight in each cage and the older chicks in groups of two or three. During a preliminary period of 3 days, the chickens were fed only such amounts of food as they would either eat completely or leave only a small amount. At the end of the preliminary period, the wire cage and excrement pans were well cleaned by scraping and washing. The chickens - were then fed slightly smaller amounts of feed for a period of 4 days, dur- ing which the excrement was collected for analysis. The feed was made up in suflicient quantity to last through the entire experiment and at the start of the collection period, was weighed into a glass fruit jar. The quantity of feed to be fed was weighed out daily. At the end of the col- lection period, the jar and its contents was again weighed and the weight of the feed removed from the jar checked against the total of the daily weighings. Any waste feed was carefully separated from the excrement each day and weighed. It was then put into a weighed jar which was again weighed at the end of the collection period to check against the total of the daily weights. The excrement was collected twice daily to avoid decomposition. It was dried at 90° C in an oven equipped with a ventilat- ing fan. The morning and afternoon collections of excrement when dried were weighed separately and put into a weighed jar. At the end of the experiment the wire screen and excrement pans were thoroughly cleaned by scraping and brushing and the excrement collected. The dried excrement in the jar was weighed as a check against the total of the daily weights. All the feed mixtures and excrements were analyzed. Protein (N x 6.25), crude fiber, fat and ash were determined by the A. O. A. C. methods. Fat was determined by extraction with ether. Am- a monia was determined in the excrement by distillation with magnesium oxide, and uric acid by the method given below. Chickens excrete the undigested residues, the solid metabolic products and the urinary products all together. A few investigators have used birds whose urinary and fecal outlets were separated, by surgical operation, but in most of the work which has been reported, the uric acid has been determined in the excrement, and correction made for its presence. The method used for determining the uric acid may affect the results for the DIGESTIBILITY OF FEEDS AND HUMAN FOODS BY CHICKENS 7 digestibility of the protein. In the work here presented the analyses of the excrement were corrected for the uric acid and ammonia present. This does not correct for metabolic products other than uric acid and am- ,monia. The figures obtained, as is usually the case, are for apparent digestibility. Methods for Determining Uric Acid The work here reported extended over a number of years and the method at first used for determination of uric acid was that of Bartlett (4), which is similar to that described below, but the uric acid in Bartlett’s method was dissolved in piperidine instead of sodium hydroxide. Studies of the method were made from time to time and some modifications made in the course of years. The methods for urikkacid and ammonia as finally used are described as follows: Texas Method for Uric Acid Weigh 1.4 grams excrement into a beaker, add 25 cc of ice-cold alcohol and allow the beaker to stand in cold water for 3O minutes. Filter off the excrement, wash twice with cold alcohol and then three times with ether. Allow to dry and return to the beaker. Add 25 cc of 0.2 N hydro- , chloric acid and allow to stand over night in the refrigerator so that the uric acid can crystallize out. Transfer to a 50 cc centrifuge tube with ice- p, cold water and centrifuge until the supernatant liquid is clear. Pour off the clear liquid. Wash the residue twice with ice water. Wash the residue into a beaker with about 2’) cc of water, add 15 cc of 0.2 N sodium hy- ‘ldroxide and heat cn the water bath with frequent stirring until the white particles of uric acid have all dissolved. This Will require about an hour. l-Transfer to a centrifuge tube, centrifuge until clear, and pour off the {clear solution to a 250 cc beaker. Wash the residue three times with hot Q water, pouring each washing into the baker. Evaporate the solution to about 430 cc, wash down the sides of the beaker with concentrated hydrochloric i’ acid and evaporate to about 2 cc. Cool and put in the refrigerator on t, ice for 24 hours to crystallize out the uric acid. Centrifuge off the precipi- jt"te and wash it twice with ice xvater. Wash the precipitate into a Kjeldahl ifltsk and determine nitrogen, distilling into 20 cc of 0.2 N hydrochloric (acid. One cc of 0.2 N acid equals 0.2% nitrogen. ' Ammonia Nitrogen in Chicken Feces , Weigh 1.4 gram into a Kjeldahl flask, add 200 cc water, two or three gpieces of sharp glass, one drop of lubricating oil and about 2 grams mag- Qnesium oxide. Distill immediately into 10 cc 0.2 N acid, titrate and ireport the ammonia as nitrogen. Studies of Other Methods for Correction for Uric Acid Two other methods recommended for the correction for uric acid were compared with the Texas method as described above, which for purposes ‘of discussion is called the Texas method. 8 BULLETIN 663, TEXAS AGRICULTURAL EXPERIMENT STATION The method of Daikowc(3), instead of determining the uric acid di "-5 supposedly gives the undigested nitrogen from which the undigested tein was calculated by multiplying by 6.25. p Weigh 1.4 grams of excrement into a 600 cc beaker. Add 500 cc n5 water and neutralize with 0.10 N sodium hydroxide using phenolphth as an indicator. Boil for one minute with constant stirring and Wash the residue back into the flask with as much hot water as previ added and filter. Transfer the residue and filter paper to a Kjeldahl and determine the nitrogen. The method of Shirley and Van Landingham, (15) determines the"! acid by difference and was slightly modified by adding dilute acid f, dry excrement to decompose any salts of uric acid which might be pr Weigh two samples of 1.4 gram each into two beakers. Add 14 cc I! hydrochloric acid, (5 cc concentrated acid to 95 cc water) and allot stand in the refrigerator over night. Transfer quantitatively to a 7; centrifuge tube and centrifuge until clear. Pour ofl’ the supernatant i. and wash once with 25 cc cold water. To one of the portions add, water, a few wrops of phenolphthalein and about twice as much i‘ diethanolamine as is necessary to make the solution alkaline, usually ‘A 8 cc, and dilute to 25 cc. To the other portion of the sample add 25 normal hydrochloric acid. Digest in a water bath at 60° C, with fre i‘: stirring, for 10 minutes. Remove and allow to cool to room tempera Mix well with a glass rod, rinse down the sides of the tubes with a water and centrifuge for 5 minutes at 1500 revolutions. Pour-off y? supernatant liquid and allow the tubes to drain for a few minutes. ; sample extracted with diethanolamine is washed three times with ccld water or until the wash water is not longer alkaline to phenolplr lein. The acid extracted sample is washed only once with cold water. A residues are trmsferred to Kjeldahl flasks and total nitrogen determ'i The differences in nitrogen between the portion extracted with hyd"ochl acid and the portion extracted with diethylanelamine are considered, represent the nitrogen present as uric acid. ‘A Results of Comparisons » The undigested nitrogen as secured by the Daikow method is given Table 1. The results are very much lower than those secured by Q Texas method, which were obtained by subtracting the sum of the acid nitrogen and ammonia nitrogen from the total nitrogen. It is evid' that the boiling water used in the Daikow method dissolves other nitro’ nous compounds in addition to the uric acid and the ammonia nitro this accounts for the incorrect values for the undigested nitrogen. The I results for undigested nitrogen in the excrement give high values for ~ gestibility of protein. This is shown by Table 2, calculated from the resu ' in Table 1. The two digestion experiments on the same feed check equa p, \ DIGESTIBILITY OF FEEDS AND HUMAN FOODS BY CHICKENS 9 . Table 1. Undigested nitrogen in experiments as determined by the Daikow ' or the Texas method Undigested nitro en Undigested nitrogen T" Sample number Daikow metho Texas method h» per cent per cent 0 - . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 .01 3.03 , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.97 3.07 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.79 2.87 ....‘ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1.22 3.26 15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.95 2.83 ~ 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1.93 4.14 l7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 .74 3.67 ,. 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.18 2.74 f’- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0. 83 3 .09 "w . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 .79 4.04 .1.‘ s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 .49 3 . 72 *4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.95 3.02 Table 2. Digestible protein calculated from analyses by two methods for uric acid Digestible protein E Digestible protein i’ Feed number D. E. Daikow method Texas method * numner per cent per cent I 470 93.49 80.60 476 94 .38 79.07 . . . . . . . . . . . . . . . . . . . . . .. 471 5.1.77 60.87 __ 477 84.59 65.22 ’ 1 . . . . . . . . . . . . . . . . . . . . . .. 472 ‘ $8.21 58.65 " 47s s4 . 43 61.13 11 . . . . . . . . . . . . . . . . . . . . . .. 47s 88.11 72.42 479 90.56 69.98 Table 3. Nitrogen in uric acid determined by two metnods Shirley and Van Landingham Texas method Excrement Number method per cent per cent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.37 3.63 .' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.30 2.70 x; . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.22 2.26 ’ é . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.00 1 .90 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 12 1 .88 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.23 1 .93 I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.73 4.05 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.73 2.93 a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.17 2.81 < . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.16 2. 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.56 2.27 ‘ ‘ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.61 2.14 - . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 .98 1 .98 f Average (13) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.78 2 .51 10 BULLETIN 663, TEXAS AGRICULTURAL EXPERIMENT STATION as well with both methods but by the method of Daikow the digestibility l’ protein is from 15 to 20% higher than when the uric acid and ammo r were determined directly. The results secured by the method of Shirley and Van Landingham given in Table 3. As a rule the Shirley and Van Landingham method gal results that are slightly higher than those by the Texas method. The meth required a larger number of determinations to secure two results w, were sufliciently close together than did the Texas method. As there Y‘ two nitrogen determinations to be made instead of one, both nitrogen terminations had to agree in order to obtain a satisfactory result on p’ uric acid nitrogen. The analyses are always repeated and if the two are sufficiently close together, continued until satisfactory agreement is cured. For the 13 analyses reported above, the Texas method requ' only 37 determinations to obtain satisfactory agreement, while the Q method required 54 runs or 108 nitrogen determinations. Ammonia was l.- determined in the Shirley and Van Landingham method. - In another experiment, pure uric acid was dissolved in a solution sodium hydroxide and precipitated with acid as in the Texas method. H‘, results were slightly low, showing that the uric acid is slightly in water and thus was not completely recovered. There is still need y improvement in the methods for determining uric acid. Digestibility of the Feeds The digestibilities of the feeds tested were calculated from the resul, obtained with the mixtures or the rations by use of the coeflicients of ~l gestibility of the other feeds in the mixture, given in Table 4. The figu g in Table 4 were calculated from a number of the earlier experiments =, are slightly different from the average digestion coefficients finally cured for the feeds. The average composition of the feeds used in the experiments is giv in Table 5. On account of the large number of tests made, the results r Table 4. Digestion coeflicients to be used in calculation of digestibility of feeds from ~ secured with balanced mixtures (chickens) Nitroge Protein Ether Crude free extract fiber extract. Alfalfa leaf meal . . . . . . . . . . . . . . . . . . . . . . . . .. 47.2 59.1 4.3 17.6 Bone meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 41.4 86.3 0 0 Buttermilk, dried . . . . . . . . . . . . . . . . . . . . . . . . .. 65.4 95.2 0 72.1 _~ Casein . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86.1 0 0 48.2 Cod liver oil concentrate . . . . . . . . . . . . . . . 0 72.9 0 0 ; Corn meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 85.1 82.8 13.0 88.5 Cottonseed meal . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.8 98.6 11.0 26.0 _ Skim milk dried . . . . . . . . . . . . . . . . . . . . . . . . . .. 65.4 95.2 0 72.1 Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60.0 100 0 99.0 " Tankage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 .4 86.3 0 0 1 Wheat gray shorts . . . . . . . . . . . . . . . . . . . . . . . . 71.1 83.6 2.1 50.1 '~ Yeast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 74.8 28.4 0 52.4 1 DIGESTIBILITY OF FEEDS AND HUMAN FOODS BY CHICKENS 11 Table 5. Average composition of feeds used for digestion experiments with chickens g5‘ Nitro- i Number Protein Ether Crude gen-free Water Ash averaged extract fiber extract s % % % % % % 1 7 Alfalfaleafmeal........ 21.9 2.8 15.6 39.4 8.1 12.2 ; 4 Barley, whole . . . . . . . . .. 10.9 1.6 5.1 69.7 10.1 2.6 ‘Q 1 Barley, without hulls. . . 13.7 1.0 1.0 73.0 9.9 1.4 r 4 Beans, lima, raw....... 21.1 1.2 5.2 60.0 8.1 4.4 f 5 Beans, navy, raw....... 22.7 1.4 5.0 58.4 8.5 4.0 . 1 Beans, pinto, raw....... 21.6 1.0 3.7 56.6 12.3 4.8 I 1 Beef, dried chipped..... 61.1 9.7 0.0 1.2 3.1 24.9 3 Beet pulp, dried . . . . . . .. 7.9 0.2 18.4 59.6 9.9 4.0 2 Broom corn seed . . . . . .. 9.2 3.7 5.2 69.0 10.3 2.6 1 Buckwheatflour........ 16.1 3.7 2.1 64.9 10.5 2.7 3 Buttermilk, dried . . . . . .. 35.3 7.4 0.2 39.5 7.1 10.5 1 Cane seed, red t0p...... 7_.8 4.3 2.5 72.2 11.6 1.6 11 Casein . . . . . . . . . . . . . . .. 82.5 0.4 0.2 4.0 9.0 3.9 3 Citrus pulp, dried . . . . .. 5.5 2.7 11.3 63.6 9.7 7.2 3 Cocoanut oil meal . . . . .. 20.8 7.8 10.6 46.4 7.9 6.5 1 Collards, dried . . . . . . . .. 2.9 0.4 1.5 5.5 87.7 2.0 5 Corn bran . . . . . . . . . . . .. 9.1 7.2 12.3 61.4 7.7 2.3 6 Cornglutenfeed....... 24.7 1.5 8.5 50.2 9.7 5.4 3 Corngluten meal....... 44.7 1.6 5.0 36.1 8.7 3.9 62 Corn meal . . . . . . . . . . . .. 10.8 3.8 1.4 71.7 10.7 1.6 " 1 Corn meal . . . . . . . . . . . .. 11.1 3.4 1.2 72.5 10.5 1.3 .1 3 Cottonseed flour . . . . . . .. 57.0 7.2 2.1 21.6 5.6 6.5 I. 1 Cott0nseedhulls....... 3.0 0.3 40.7 43.8 9.5 2.7 j. 10 Cottonseed meal....... 42.8 6.5 9.9 27.7 6.8 6.3 3‘ 3 Fish meal . . . . . . . . . . . .. 66.3 3.6 0.3 6.7 7.3 ' 15.8 F 1 Flour,clear............. 16.3 1.3 0.3 64.9 16.6 0.6 2 Flour, graham... 12.4 1.8 1.8 70.3 12.3 1.4~ 2 Flour, low grade. 16.9 2.0 0.5 67.6 12.1 0.9 6 Flour, patent... 13.4 0.9 0.3 72.5 12.4 0.5 1 Gelatine . . . . . . . . . . . . . .. 94.0* 0.1 0.0 0.0 14.3 1.9 1 Hegari seed . . . . . . . . . . .. 10.3 2.7 1.9 73.6 10.2 1.4 3 Kafir . . . . . . . . . . . . . . . .. 12.0 3.5 2.3 70.8 9.6 1.6 1 Lactose . . . . . . . . . . . . . .. 0.2 0.0 0.0 98.8 1.0 0.4 2 Linseed oilmeal........ 37.3 6.5 7.8 33.5 9.0 5.9 1 Liver meal . . . . . . . . . . . .. 64.0 17.8 1.2 2.3 9.2 5.5 1 Macaroni . . . . . . . . . . . . .. 14.3 0.9 0.4 74.9 8.9 0.7 2 Meat meal . . . . . . . . . . .. 47.6 8.3 1.6 3.4 6.5 32.6 2 Meat and bone meal.... 51.0 9.1 2.0 0.9 5.8 31.2 6 Milk, dried, skim . . . . . .. 35.0 1.1 0.2 49.8 6.3 7.6 2 Millet seed . . . . . . . . . . .. 10.9 3.8 9.8 62.0 9.9 3.6 4 Milo . . . . . . . . . . . . . . . . .. 11.2 2.8 2.3 71.6 10.4 1.7 5 Oat hulls . . . . . . . . . . . . .. 4.6 1.3 29.3 50.3 7.7 6.8 3 Oat meal . . . . . . . . . . . . .. 15.8 5.9 1.5 65.5 9.5 1.8 1 Oats, red . . . . . . . . . . . . .. 10.5 5.9 11.9 57.4 10.4 3.9 6 Peas, cow, raw . . . . . . . .. 23.0 1.1 3.8 59.0 9.4 3.7 5 Peanut meal . . . . . . . . . .. 43.9 7.4 9.9 25.6 6.6 6.6 . 2 Rice . . . . . . . . . . . . . . . . .. 7.8 0.3 0.4 78.3 12.2 1.0 4 Rice bran . . . . . . . . . . . .. 12.5 12.4 11.4 41.5 9.1 13.1 - 1 Rice hulls, ground..... 2.3 0.8 40.4 26.9 9.3 20.3 ' 4 Rice polish . . . . . . . . . . .. 13.3 14.5 2.5 49.8 10.0 9.9 l 1 Rye flour . . . . . . . . . . . .. 12.6 1.9 2.2 69.7 11.8 1.8 g 3 Rye seed . . . . . . . . . . . . .. 13.5 1.6 2.7 69.9 10.5 1.8 1 3 Shrimp meal . . . . . . . . . .. 46.8 2.8 11.0 1.3 9.7 28.4 a 1 Seed, cane............. 9.3 3.2 2.0 73.7 10.6 1.2 3 Solvent process soybean oil meal . . . . . . . . . . . .. 47.0 0.5 5.7 32.2 3.7 5.9 a 1 Soybean oil meal . . . . . .. 46.0 4.7 5.4 29.3 9.2 5.5 8 Starch . . . . . . . . . . . . . . .. 0.6 0.1 0.2 87.9 11.3 0.1 1 Sugar . . . . . . . . . . . . . . . .. 0.1 0.0 0.1 99.7 0.1 0.0 2 Sunflower seed . . . . . . . .. 19.1 28.0 31.5 12.4 5.9 3.1 5 Sweet potato . . . . . . . . .. .4 0.8 2.9 68.2 20.8 3.9 6 Tankage . . . . . . . . . . . . .. 59.6 8.8 1.7 1.0 6.8 22.1 2 Wheat . . . . . . . . . . . . . . .. 15.3 1.8 2.6 68.7 9.7 1.9 , 2 Wheatbran (humanfood) 12.9 2.0 9.1 61.9 6.4 7.9 6 Wheatbran............ 18.6 3.9 9.5 51.6 10.0 6.4 9 Wheatgray shorts...... 19.1 4.2 5.9 55.4 10.8 4.4 5 Yeast . . . . . . . . . . . . . . . .. 51.8 0.8 3.2 29.3 6.4 8.5 ‘FNX 6.25. The factor 6.25 is too high for gelatine. _:' _ . 4Y1" Table 6. Digestion coeflicients and standard deviations, chickens Digestion coefficients Standard deviations Number Name N itrogen- Nitrogen- averaged Protein Ether Crude free Protein Ether free extract fiber extract extract extract % o % o 2 Albumen, blood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Albumen, e83, not cooked . . . . . . . . . . . . . . . . . . .. 48.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Alfalfa leaf meal . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 56.3 58.6 6.6 36.6 8.2 14.8 11.0 1 Barley, no hulls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.7 77.5 24.8 80.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Barley, whole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 73.4 75.3 11.6 79.6 13.8 16.4 3.2 4 Beans, lima, raw . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 34.5 92.3 13.7 68.5 10.1 15.5 16.9 2 Beans, lima, cooked . . . . . . . . . . . . . . . . . . . . . . . . . . 74.0 74.2 12.6 75.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Beans, navy, raw . . . . . . . . . . . . . . . . . . . . . . . . . . .. 41.9 63.7 16.0 40.8 9.1 49.3 17.6 3 Beans, navy, cooked . . . . . . . . . . . . . . . . . . . . . . . . . 59.8 71.9 7.2 66.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Beans, pinto, raw . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43.4 96.8 28.3 38.7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Beef, dried . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 85.9 96.6 0 100.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11 Beet pulp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 27.2 54.1 3.6 23.0 28.6 42.9 10.1 5 Broom corn seed . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 46.3 90.7 13.2 82.2 11.4 3.5 2. 1 Buckwheat flour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85.8 74.4 0 88.9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Buttermilk, dried . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69.1 95.4 0 70.5 8.3 13.6 2 Cane seed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 69.2 76.2 22.0 89.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 37 Casein . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 85.1 48.2 38.5 . . . . . . . . .. 3.4 . . . . . . . . . . . . . . . . . . .. 12 Citrus pulp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 16.3 70.2 5.5 41.8 15.8 24.7 6.9 8 Cocoanut oil meal . . . . . . . . . . . . . . . . . . . . . . . . . .. 56.4 92.1 15.4 31.5 4.8 12.6 4.0 1 Collards, dried . . . . . . . . . .' . . . . . . . . . . . . . . . . . . . . . 69.8 64.9 13.4 52.7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Corn bran . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 53.9 89.2 6.8 33.1 13.1 7.2 7.1 11 Corn gluten feed . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 61.7 65.3 3.3 43.7 6.2 22.1 11.1 10 Corn gluten meal . . . . . . . . . . . . . . . . . . . . . . . . . . .. 80.5 55.1 10.8 56.5 5.4 34.9 39.0 117 Corn meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 86.1 89.5 21.6 94.1 11.6 12.2 3.7 11 Cottonseed flour . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 73.2 86.5 13.5 38.1 4.9 11.7 16.8 1 Cottonseed hulls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ 0 31 .3 9.2 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Cottonseed hulls, delinted . . . . . . . . . . . . . . . . . . . . . 14.3 32.5 6.0 4.7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Cottonseed mea . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 70.0 96.7 10.4 36.2 10.8 10.1 25.1 10 Fish meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 74.8 82.7 49.8 35.1 4.6 9.3 38.8 4 Flour, clear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 89.7 96.9 64.6 99.0 7.2 4.7 1.9 3 Flour, raham . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.9 98.7 44.1 90.4 . . . . . . . . - - . . . . . . . . . . . . . . . . . . . . 9 Flour, ow grade . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 84.2 95.9 82.8 89.4 6.0 5.6 7.0 15 Flour, patent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 85.8 96.9 81.4 95.0 6.7 7.4 4.9 4 Gelatine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 . . . . . . . . . . . . . . . . . . . . 1 He ari grain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 86.0 76.9 41.9 94.9 . . . . . . . . - . . . . . . . . . . . . . . . . . . .. 8 Kair grain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 79.7 79.9 12.4 93.1 12.2 7.0 2.3 2 Lactose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 0 0 45.8 . . . . . . . . - - . . . . . . . . . . . . . . . . . . . . 6 Linseed oil meal . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 62.2 76.1 9.1 23.6 8.7 11.6 22.4 Z1 NOLLVLS LNEIWIHGIJXCII "IVHILUIIIOIHDV SVXELL ‘S99 NLLEITIIIH uaommaawaraaw Om. wmmum >ZU mcFwz mooum MN OMHOWHZM S 495565 . . . . . . . . ..37 9 12 6 81 467 8284 ..6T65T4HHHHHH...H23 7 20.6 85 543 7967 1211 . . . . . . . . . . 11 31 . 220655431HHHHHHH124648l945672070452633627 a .........HHHHHHH.K60567669594057758957233 .~ fiW%%%%%%% . . . . . ..W&75961877583329618893665 x H H H H H H H . 540 2269 HHHHHHH19l508078675316HH76674942 < ...H.... HHHHHHH..K...KZ6 .05.. 9956478 .H %w%.U%9%0 . . . . . ..v6mem43m1nun1 ..n123 1 wnufi o - : | | a u 2140525475432877912906570061375W.0e1fi4J5fi 50 002 68870..53856557 M%%MMM%%MN%M%%%%%99%mM495M88734..97898784 1 .. 666939510 H H H H H H H7697O9 71966225 H H53436007 i... 70407056 . . . . . . . 22308066485453 . .58538788 a M76778285 . . . . . . ._H.777w5 76656775 H H63595566 a éddkéd corn......... cottonseed. . . . medium hydro high hydrogenate . peanut... cod liver. . soy bean. s, canned. Peas, blackeye %hum seed. . y ean o1l meal, vent process s Soybean oil meal ar, cane..... round who Total v 9 | s ) a 9 1l 1] 1l l l Rice, polished. . Rice bran. . Rice hulls. . Rice polish. Rye seed. .. Rye flour. . Shrimp meal. . . Sor So So StarchIIvIIIIIU Sug Sunflower seed. . Sweet potato. . . Tankage. . . . . H Wheat, g . . . . Wheat bran............ Wheat bran (human food). Wheat gray shorts. . . . . . Yeast.................... O O O O1 O Oll O Pea Liver Macaroni................................ Meat meal, meat scraps, meat an Milk, dried skim.. Millet seed. . . . .. Milo, grainHH... Oat hulls......... Oat meal......... Oats, red whole... l 1 Peas, blackeye, raw Peanut rnealHH 31626007513523454215529410039366331500 3 111 1 1 1. l 3 1 2 2 13 4 17 ll 718 14 BULLETIN 663, TEXAS AGRICULTURAL EXPERIMENT STATION each individual digestion experiment are not given. Table 6 contains ave _ coeflicients of digestibility and also the standard deviations if there 4 or more tests on the same feeds. The standard deviations are not gi, for the crude fiber. 4' For comparative purposes, the average coefficients of digestibility n; Bulletin 372 (4) are given in Table 7. Average coefficients compiled f l a number of results, published since Bulletin 372 was prepared, are gi“ in Table 8. These include foreign experiments, in which some of the -- used are not often found in this country. The standard deviation shows the variability of the data. The aver of all of the standard deviations for the experiments in Table 6 were f; for protein, 14.8 for ether extract, and 11.3. for nitrogen-free extract. g standard deviation is considered low if less than 5, medium if betw‘! 5 and 10, and high if over 10. A high standard deviation was sometil due to the results of only one or two tests being widely out of line wi‘ Table 7. Coefficients of digestibility, chickens, average from Bulletin 372 Number Protein Ether Crude averaged extract fiber % % % 2 Alfalfa leaf meal . . . . . . . . . . . . . . .. 100 0 4 2 Alfalfa meal . . . . . . . . . . . . . . . . . . . . 63 22 1 21 Barley . . . . . . . . . . . . . . . . . . . . . . . . . 72 58 l0 6 Blood meal . . . . . . . . . . . . . . . . . . . . . 91 46 18 12 Buckwheat . . . . . . . . . . . . . . . . . . . . . 61 86 10 5 Buttermilk, dried . . . . . . . . . . . . . . . 82 79 . . . . . . . . . . 81 f 43 Corn and corn meal, bolted and f unbolted . . . . . . . . . . . . . . . . . . . . . 74 87 13 90 ' 8 Cottonseed meal, Texas . . . . . . . . . . 76 86 12 86 8 Cowpea meal . . . . . . . . . . . . . . . . . . . 48 88 11 86 6 Darso . . . . . . . . . . . . . . . . . . . . . . . . . . 36 86 38 89 10 F eterita . . . . . . . . . . . . . . . . . . . . . . . . 88 81 33 91 11 Fish meal . . . . . . . . . . . . . . . . . . . . .. 91 96 . . . . . . . . .. 15 3 India wheat . . . . . . . . . . . . . . . . . . . . 75 84 21 83 17 Kafir (dwarf) . . . . . . . . . . . . . . . . . .. 67 78 18 92 6 Kafir, average for Texas only. . . . . 84 8O 19 93 7 Bone me . . . . . . . . . . . . . . . . . . . . . 87 93 24 34 2 illet . . . . . . . . . . . . . . . . . . . . . . . . . 76 78 17 87 12 Milo . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 78 31 92 11 Oat groats . . . . . . . . . . . . . . . . . . . . . 77 89 14 91 21 Oats, whole . . . . . . . . . . . . . . . . . . . . 74 82 7 69 5 Peanut meats . . . . . . . . . . . . . . . . . . . 8O 78 4 84 3 Peas . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 81 9 87 7 Potatoes, white . . . . . . . . . . . . . . . . . 47 0 6 85 3 Potatoes, sweet . . . . . . . . . . . . . . . . . 0 25 4 77 9 Rice bran . . . . . . . . . . . . . . . . . . . . . . 58 87 3 52 2 Rice, brown . . . . . . . . . . . . . . . . . . . . 84 88 7 98 4 Rice polish . . . . . . . . . . . . . . . . . . . . . 81 95 4 89 10 Rice, rough . . . . . . . . . . . . . . . . . . . . . 74 72 5 84 8 Rye . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 31 12 86 3 Shallu . . . . . . . . . . . . . . . . . . . . . . . . . . 78 85 39 94 7 Sorghum . . . . . . . . . . . . . . . . . . . . . . . 16 84 15 88 2 Soybean . . . . . . . . . . . . . . . . . . . . . . . . 70 93 53 76 5 Soybean oil meal . . . . . . . . . . . . . . . . 83 81 2 83 8 Soybean oil cake . . . . . . . . . . . . . . .. 83 82 0 80 4 Tankage, di ester . . . . . . . . . . . . . .. 85 96 4 44 9 Wheat midd ings, 6.25% fiber. . . . 50 53 9 50 4 Wheat gray shorts . . . . . . . . . . . . . . . 69 85 13 71 ~ 11 Wheat bran . . . . . . . . . . . . . . . . . . . . . 60 50 8 54 34 Wheat . . . . . . . . . . . . . . . . . . . . . . . . . 74 47 9 89 9 Wheat middlings, 8.5% fiber. . . . . 76 53 8 60 DIGESTIBILITY OF FEEDS AND HUMAN FOODS BY CHICKENS 15 Table 8. Coefficients of digetibility——chickens—compiled Nitrogen- Refer- Number Protein Ether Crude free ence ‘ averaged extract tiber extract number % % % % E 7 Alfalfa . . . . . . . . . . . . . . . . . . . . 65 55 44 61 .1, 3 ‘g 1 Alfalfa silage . . . . . . . . . . . . . . 60 55 . . . . . . . . . 53 1 1 Artichoke, Jerusalem . . . . . . . 67 . . . . . . . . . 29 . 94 3 t 3 Barley . . . . . . . . . . . . . . . . . . . . 77 80 12 86 1, 3 i, 1 Barley malt . . . . . . . . . . . . . . . 75 70 . . . . . . . . . 74 1 Q 1 Barley bran . . . . . . . . . . . . . . . 85 86 20 86 3 2 Beans . . . . . . . . . . . . . . . . . . . . . 86 75 32 86 1, 3 2 Beets . l . . . . . . . . . . . . . . . . . . . 69 74 . . . . . . . . . 87 1 1 blood meal . . . . . . . . . . . . . . . . 88 9O . . . . . . . . . 75 1 1 Bone meal . . . . . . . . . . . . . . . . 90 90 . . . . . . . . . 85 1 1 Brewers’ grains . . . . . . . . . . . . 8O 60 . . . . . . . . . 78 1 1 Buckwheat bran . . . . . . . . . . . 60 67 25 61 3 3 Buttermilk . . . . . . . . . . . . . . . . 93 92 . . . . . . . . . 94 1 1 Cabbage . . . . . l . . . . . . . . . . . . 72 57 -71 80 3 2 Carrots . . . . . . . . . . . . . . . . . . . 68 64 54 93 1, 3 9 Clover . . . . . . . . . . . . . . . . . . . . 63 61 52 65 1, 3 2 Cocoanut meal . . . . . . . . . . . . . 73 82 . . . . . . . . . 85 1 11 Corn . . . . . . . . . . . . . . . . . . . . .. 80 86 13 9 1,3,10,11 1 Corn feed meal . . . . . . . . . . .. 85 82 5 82 1 2 Corn, flaked . . . . . . . . . . . . . . . 88 78 . . . . . . . . . 95 11 3 Cottonseed cake . . . . . . . . . . . 76 73 55 73 1 3 Cod lish meal . . . . . . . . . . . . . 90 90 . . . . . . . . . 65 1 1 Flax seed . . . . . . . . . . . . . . . . . 9O 93 6 60 1 ' 4 Grass . . . . . . . . . . . . . . . . . . . . . 63 55 41 65 l, 3 1 Grass silage . . . . . . . . . . . . . . . 6O 6O . . . . . . . . . 58 1 ’ 1 Hemp seed . . . . . . . . . . . . . . . . 75 9O . . . . . . . . . 65 1 1 Lentils . . . . . . . . . . . . . . . . . . . . 86 63 53 93 3 2 Linseed cake . . . . . . . . . . . . . . 82 83 . . . . . . . . . 8O 1 2 Lupine meal . . . . . . . . . . . . . . . 82 69 . . . . . . . . . 80 1 1 Meat meal . . . . . . . . . . . . . . . . 90 90 . .‘ . . . . . . . 85 1 1 Millet . . . . . . . . . . . . . . . . . . . . . 9O 73 5 88 12 2 Milk, skim . . . . . . . . . . . . . . . . 93 92 . . . . . . . . . 94 1 1 Milk, whole. . . .1 . . . . . . . . . . . 95 92 . . . . . . . . . 94 1 6 Oats . . . . . . . . . . . . . . . . . . . . .. 71 81 21 73 1.l1,12 2 Oat meal . . . . . . . . . . . . . . . . . . 85 75 9 91 1 2 Palm kernel . . . . , . . . . . . . . . . 70 77 . . . . . . . . . 77 1“ » 1 Peanut cake, 0.1 t0 5.0% _; crude iibcr . . . . . . . . . . . . . . 83 81 7 82 1 1 Peanut cake, 5.1 to 10% crude liber . . . . . . . . . . . . . . 76 74 4 75 1 1 Peanut cake, 10.5 t015.0% crude liner . . . . . . . . . . . . . . 70 68 . . . . . . . . . 67 1 1 PCHDJI. meal, esatracted. . . . . 82 8O 7 81 1 14 Peas , . . . . . . , , . . . . . . , . . . . .. 75 75 14 79 1, 3, 10 3 Potatoes, Irish . . . . . . . . . . . . . 63 41 13 88 1, 3 ; 3 Rape seed . . . . . . . . . . . . . . . . . 80 86 . . . . . . . . . 79 1, 3 ‘ 1 Rice feed meal. . . . . . 67 88 . . . . . . . . . 58 3 ‘ l Rice, ground . . . . . . . . 72 85 4 68 1 i, 1 Rice. polished. . . . . . . . . . 87 50 47 97 3 2 Rutabagas . . . . . . . . . . . . . . . . 75 75 69 9O 1, 3 ‘ 2 Rye bran . . . . . . . . . . . . . . . . . 73 66 33 67 1, 3 3 Rye, grain . . . . . . . . . . . . . . . . 70 59 5 = 85 1, 3 :- 1 Soybeans . . . . . . . . . . . . . . . . . . 92 90 37 » 69 3 ‘~ 7 Soybean meal . . . . . . . . . . . . . 78 72 9 81 1. 3 * 1 Speltz bran . . . . . . . . . . . . . . . . 78 88 25 40 3 " 3 Sugar beet . . . . . . . . . . , . . . . . 7O 78 33 91 1, 3 L, 1 Sugar beet leaves . . . . . . . . .. 74 25 75 89 3 ,; 3 Sunflower seed cake . . . . . . .. 77 82 3 86 1 3 Sunflower seed meal extracted 72 75 0 8O 1 - 1 Tapioca meal . . . . . . . . . . . . . . 86 85 8 87 1 3 Turnip . . . . . . . . . . . . . _ . . . . . . 68 74 35 91 l, 3 1 Vetch . . . . . . . . . . . . . . . . . . . . . 84 75 6 80 1 5 18 Wheat . . . . . . . . . . . . . . . . . . . . 88 49 10 88 1, 11 ’ 6 Wheat bran . . . . . . . . . . . . . . . 62 53 9 46 l, 13 " 8 Wheat, coarse middlings. . . . . 76 86 5 88 13 v 1 Wheat malt sprouts. . . . . . . . 76 70 . . . . . . . . . 75 1 1 Whale meal . . . . . . . . . . . . . . . 85 90 . . . . . . . . . 60 1 l 1 Yeast, dried . . . . . . . . . . . . . . . 90 70 . . . . . . . . . 88 1 16 BULLETIN 663, TEXAS AGRICULTURAL EXPERIMENT STATION the others for the same feed. It might have been more accurate to exclude such tests from the calculations on the assumption that these differences were due to errors and not to actual differences in digestibility. High standard deviations occurred when the feed had a low content of the nutrient being studied, such as ether extract in dried beet pulp, in citrus pulp, in dried skim milk, or in oat hulls, or protein in beet pulp or oat hulls. Low standard deviations are found in feeds with a high content of the nutrient studied, such as protein in casein, in coconut oil meal, in corn gluten meal, or peanut meal, and nitrogen-free extract in barley, broom corn seed, corn meal, and flour. The data show that variations in digest- ibility are much greater with some kinds of feeds than with others. The actual variations may not be as great as they appear from the table, be- cause the digestibility of the different feeds were determined with mix- tures and rations and part of the variations are no doubt due to differences in the digestibility of the other feeds in the mixture, while all the variation i i is assigned to the feed being studied. This is shown below. Effect of Percentage of Protein on Digestibility The digestibility of corn meal was calculated from experiments on 3 series of rations containing 17, 24 and 31 per cent protein and differing only in the percentages of casein and corn meal present. The ration fed in series 17 consisted of 60% corn meal, 16.3% wheat gray shorts, 10% dried skim milk, 4% alfalfa leaf meal, 6% yeast, 1.5% oyster shell, 1% tricalcium phosphate, 1% salt, and 0.2% cod liver oil concentrate, and contained approximately 17% protein. The ration fed in series 24 contained 10% casein in place of 10% corn meal, and contained 24% protein while series 30 contained 20% casein in place of 20% corn meal, with 31 per cent protein. The average digestion coefficients of the rations and those of the corn meal fed in the rations were calculated from the data from the rations and are given in Table 9. The differences in protein content of the rations had practically no effect upon the digestibility of the protein or the nitrogen- free extract of the corn meal. The digestibility of the ether extract decreased as the protein content of the rations increased. When the digestibility of the constituents of the corn meal was calculated from the results with these rations (Table 9), the digestibility of the ether extract was lower in the ration containing 31 per cent protein than in the other two, and the difference was found by statistical analysis to be significant. Barnes, Prim- rose, and Burr, 1944, (2) comparing the results obtained from rats on diets containing 12 or 28% casein, and 14 or 30% protein, concluded that the lower protein intake is associated with a lower digestibility of fat. The results here reported are exactly the opposite, since the lower protein intake is associated with a higher digestibility of fat, though they relate to the natural fat in the feeds and not to butter fat or lard, and to chickens and not rats, as was the case with the work of Barnes, et al. Table 9. Digestion coelficients of rations and of corn meal in rations. Digestion coefficients Standard deviations Number Name Nitrogen- — —&i—trogen- averaged Protein Ether Crude free Protein Ether free extract fiber extract extract extract 26 Corn meal ration about 17% protein . . . . . . . . . . .. 75.1 88.2 7.7 81.0 2.3 2.1 1.9 2O Corn meal ration about 21% protein . . . . . . . . . . . . 79.2 87.3 4.9 78.3 2.2 2.0 2 .1 24 Corn meal ration about 31 % protein . . . . . . . . . . .. 80.8 83.3 5.5 79.1 1.8 3 .1 2.3 26 Corn meal in ration 17% protein . . . . . . . . . . . . . . . 83.9 93.3 20.6 94.5 7 8 7.7 5.3 20 Corn meal in ration 24% protein . . . . . . . . . . . . . .. 85.3 88.1 17.9 94.3 10.1 9.5 4.5 24 Corn meal in ration 31 ‘Y4. protein . . . . . . . . . . . . . . 86.5 79.4* 22.7 95.3 18.5 15.8 5 5 *Difference from 93.3 statistically rri: Jfcui-t LI SNEDIOIHO LEI SGOOeI NVWHH (INV SGEIEIJ cIO LLYIIHLLSEISIG 18 BULLETIN 663, TEXAS AGRICULTURAL EXPERTMENT STATION i Variations of Digestibility of Rations. Compared with Digestibility Of the Chief Feed in the Rations The standard deviations of the coeflicient of digestibility of the prot in the series of rations discussed above (Table 9) ‘in which casein repla‘ corn meal were 2.3, 2.2, and 1.8 compared with standard deviations of 10.1 and 18.5 for the coefficients of digestibility of the protein of the col meal, as calculated from the data of the same rations. The stand!“ deviations of the digestion coeflicients for the ether extract in the ratio, were 2.1, 2.0 and 3.1 compared with 7.7, 9.5 and 15.8 for that of the meal calculated from the same rations. For nitrogen-free extract standard deviations were 1.9, 2.1 and 2.3 for the rations compared -l 5.3, 4.5 and 5.5 for the corn meal. This shows that the variability of digestion coefiicients calculated for a feed fed in a ration may be m l greater than that of the entire ration. Comparatively small deviatid in the digestion coefficients of a mixture may result in much larger de‘ tions in the digestion coefficients of a feed which is a part of the mixt i Part, at least, of the variations of the digestibility of a feed fed int mixture is due, not to variations in the digestibility of the feed, but’ i- variations in the ration, or to small errors which are magnified wh the digestibility of the feed is calculated from the digestibility of the tion in which it was fed. For example, in experiment 433, the ration ea (363.5 grams) contained 111.74 grams of protein, of which 11.25 gra" was from the corn meal. An error of 0.5 gm. in the protein digestl would affect the digestibility of the protein in the entire ration less 3f 0.5 per cent, but it would effect the digestibility of the protein in the co meal 4.5 per cent. For this reason, errors which would have only a smf effect on the constituents of the entire ration will have a much lar' effect on a constituent of the ration. A Comparisons of Mixtures and Rations Digestion experiments were made (a) on the unmixed feeds, (b) in m" tures containing a large percentage of the food to be tested, balanc' with starch if the food was a protein food or casein, if it was a cart‘ hydrate food and (c) complete rations in which the food to be tes =3 was 50 per cent or less of the ration. The complete rations were used ‘i determining the productive energy of the feeds, and are described =1‘- where (6, 7, 8). l‘ There were suflicient numbers of experiments for some comparisons Y be made of the digestion coefficients secured from the feed fed in r” tions with those secured when it was fed in the balanced mixtures. The_ comparisons are given in Table 10. The coefiicient of digestibility of th protein in dried buttermilk was significantly lower in the ration than the balanced mixture, that of cottonseed meal was significantly lower whe? fed alone than when fed in a ration. The digestibility of the ether extract; was significantly lower when fed in a ration containing 31 per cent tein, due to casein, than in a ration containing 17 per cent. The coeflicien t‘ Table l0. Digestion coeflicients of chicken feed in rations (R) as compared with balanced mixtures (M) or alone (A) Standard deviation Nitrogen- Number Protein Ether Crude free _ Nitrogen- averaged extract fiber extract Protein Ether free Class "/0 % % % extract extract 6 Alfalfa leaf meal . . . . . . . . . . . . . . . . . .. 61.4 51.0 13.4 26.4 6.8 11.6 15.2 M 14 Alfalfa leaf meal . . . . . . . . . . . . . . . . . .. 54.1 61.8 3.7 40.9 10.7 20.0 10.8 R 4 Buttermilk, dried . . . . . . . . . . . . . . . . .. 76.5* 96.8 . . . . . . . . .. 69.7 3.1 2.7 17.4 M 8 Buttermilk, dried . . . . . . . . . . . . . . . . . . 65.4 94.5 . . . . . . . . . . 72.2 7.6 10.4 11.0 R 9 Corn meal . . . . . . . . . . . . . . . . . . . . . . . .. 70.1** 89.9 9.9 90.5 7.4 1.6 3.0 A 117 Corn meal . . . . . . . . . . . . . . . . . . . . . . . .. 86.1 89.5 21.6 94.1 11.6 12.2 3.7 A11 13 Casein . . . . . . . . . . . . . . . . . . . . . . . . . . .. 84.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3.0 . . . . . . . . . . . . . . . .. M 24 Casein . . . . . . . . . . . . . . . . . . . . . . . . . . .. 85.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3.6 . . . . . . . . . . . . . . . . . . .. R 6 Cottonseed meal . . . . . . . . . . . . . . . . . .. 629* 93.0 12.2 55.1* 14.4 16.0 35.0 M ll Cottonseed meal . . . . . . . . . . . . . . . . . .. 73.9 98.7 9.4 25.9 5.9 2.8 7.9 R 6 Flour, patent . . . . . . . . . . . . . . . . . . . . .. 89.6 97.4 62.2 97.4 4.8 6.3 1.5 M 9 Flour, patent . . . . . . . . . . . . . . . . . . . . . . 83.3 96.6 94.2 93.4 6.9 8.5 5.8 R 5 Peanut meal . . . . . . . . . . . . . . . . . . . . . .. 74.6 92.4 4.5 55.2 3.7 2.2 5.6 M 10 Peanut meal . . . . . . . . . . . . . . . . . . . . . .. 73.2 90.2 7.6 48.4 3.8 5.8 11.1 R 5 Rice polishings . . . . . . . . . . . . . . . . . . . .. 678* 91.2 10.3 79.3** 4.4 2.9 6.5 M 6 Rice polishings . . . . . . . . . . . . . . . . . . .. 76.5 90.4 16.5 90.3 6.3 2.5 2.5 R 6 Milk, dried skim . . . . . . . . . . . . . . . . . .. 77.7 85.3 100.0 62.6 9.9 31.9 21.7 M 6 Milk, dried skim . . . . . . . . . . . . . . . . . .. 72.2 28.7 19.1 68.5 5.7 34.0 10.9 R *Difference statistically significant **Difference highly significant 61 SNEDIOIHO 2R8 SCIOOJ NVWHH CINV SCIEIEIJ JO LLYIIEIILSEIDICI . then that cooked at a higher temperature. 20 BULLETIN 663, TEXAS AGRICULTURAL EXPERIMENT STATION of digestibility of the nitrogen-free extract of cottonseed meal was l nificantly higher when fed in a balanced mixture than when fed in a rati The other differences shown in the comparisons in Table 10 are apparen not significant. The differences were not in the same direction significant. As a general rule, the mixtures and the rations may be =I sidered to give the same results. ” Discussion of Some Individual Feeds The digestibility of the protein and of the nitrogen-free extract ' raw beans (Table 6) was appreciably less than that of the cooked Raw beans are evidently not good chicken feed. The digestibility of w‘ black-eye peas was nearly the same raw as when cooked. i3 The soybean oil meal cooked at a low temperature was less digesti, The protein of dried beef Was digested 85.9 per cent, compared with “if per cent for meat scraps, meat meal and meat and bone tankage n“ 55.4 for tankages. Dried beef consists of the muscle, while tankage n: meat by-products are made from animal by-products not suitable human food, and may contain little muscular tissue. f The constituents of wheat bran, wheat gray shorts and graham N are almost all less digestible than those of the various grades of fio" Wheat bran and wheat gray shorts contain smaller percentage of sta than flour, and larger percentages of pentosans. The graham flour co‘, tains wheat bran and wheat gray shorts, which accounts to some ext =3‘ for the constituents of the graham flour having lower digestibility t , those of patent flour or low grade flour. Lactose (milk sugar) had a lo? digestibility. It had a laxative effect, when fed as 15 per cent of the ratio v and not only had a l_ow digestibility but the digested lactose had a l i? productive energy (8). Cottonseed oil hydrogenated to a medium degree (iodine number ,5: had a digestibility practically the same as unhydrogenated oil. When hydr p. genated to a high degree (iodine number 10) the digestibility was onl l half that of the moderately hydrogenated oil. The productive energy ~ the digested oil when highly hydrogenated was also lower than that '0, the medium hydrogenated oil. ‘ g The factor for converting nitrogen to protein in gelatin should be 5. l and not 6.25. However, to use one factor for gelatin and a different factors for the other feeds in calculating the protein in the same mixture is not cor-d rect. Nitrogen could be used for calculating the digestibility of the protein; and then the nitrogen-free extract could be calculated by diflerence. Wit ' use of the correct factor for protein, the nitrogen-free extract for gelati is 0 but it is not 0 in the ration used due to the presence of other feeds. It seems simpler to use the factor 6.25 throughout and to calculate the nitrogen-free extract separately for the mixture, even though both thes analysis of the mixture and the gelatin add to more than 100%. With the factor 6.25 the constituents of the gelatin add to 110 per cent. A ' I-\"|>11’-< __..--_,....--w-.w , DIGESTIBILITY OF FEEDS AND HUMAN FOODS BY CHICKENS 21 ACKNOWLEDGEMENT Feeding the chickens, analyses of the samples and other work was done by E. C. Carlyle, S. M. Greenberg, and other members of the staff. SUMMARY Average digestion coefficients are given for 718 digestion experiments with l chickens. Methods for determining uric acid were studied. The digestion coefficients for the individual feeds were calculated from experiments with ~» balanced mixtures 0r rations. The standard deviations of the digestion coefficients were calculated when 4 or more experiments were made on the same kind of feeds and show the variability of the digestion coefficients. The standard deviations were often high for nutrients which were present in low percentages in the feed. The standard deviations are high in some cases, and this indicates wide variability in the results. These variations are evidently due to errors in the work rather than to differences in the digestibility of the nutrient. Low standard deviations were found with many feeds, especially for nutrients present in high percentages. With 3 groups of mixed rations which differed only in their per- centages of casein and corn meal, the digestion coefficients of the protein and nitrogen-free extract were in the limits of error. The fat was di- gested to a smaller extent from the rations high in protein than from those low in protein. When the standard deviations were, compared for the coefiicients of digestibility of rations containing corn meal and for those of the corn meal contained in these rations calculated from the data se- _ cured from these experiments, the standard deviations were much higher for the corn meal than for the entire ration. This shows that small varia- tions in the digestibility of rations may appear as much larger variations in the digestibility of individual feeds fed as part of these rations. Tables are given showing the digestion coefficients secured with the various feeds and foods used, and also tables showing the coefficients of digestibility . secured in previous work at this station and also by other workers. 22 10. 11. 12. 1'3. 14. 15. iHalnan, E. T. 1928. Digestibility of weak and strong wheats. J. Agr. Sci. 18: 4 BULLETIN 663, TEXAS AGRICULTURAL EXPERIMENT STATION V REFERENCES Axelsson, Von Loel. 1937. Der allgemein nahrwert unserer gewohnlichsten fu fur Huhner. (Compilation). Annalen der Landwirtschaftlichen Hoc Schwedens 4: 131-68. Barnes, R. H., M. F. Primrose, and G. O. Burr. 1944 The influence of the p.“ content of the diet upon fat digestibility. Jour. Nut. 27, 179-185. -_ Diakow, M. J. 1931. Untersuchung uber verdaulichkeit, stoff und energeiwechaclf‘ Huhner. Arch. fur Tierernahrung und Tierversucht 7: 571-637. ' ’_ Fraps, G. S. 1928. Digestibility and production coefficients of poultry feeds. Agr. Exp. Sta. Bul. 372. y’ Fraps, G. S. 1937. Digestibility by chickens of the nitrogen-free extract of feeds. Agr. Exp. Sta. Bul. 437'. Fraps, G. S. and E. C. Carlyle. 1939. The_ utilization of the energy of feed by ing chicks. Tex. Agr. Exp. ‘Sta. Bul. 571. Fraps, G. S. and E. C. Carlyle. 1941 Productive energy of corn meal, alfalf meal, dried buttermilk and casein as measured by production of fat and fl growing chickens. Tex. Agr. Exp. Sta. Bul. 0O. Fraps, G. S. and E. C. Carlyle. 1942. Productive energy of some feeds and ; as measured by gains of energy by growing chickens. Tex. Agr. Exp. Sta. Bu]. Fritz, J. C. 1936. The effect of grinding on the digestibility of Argentine flint Poultry Science 5: 267-272. .», Fritz, J. C. 1937. The effect of feeding grit on the digestibility of the domestic Poultry Science 16: 75-79. Halnan, E. T. 1928. Digestibility of oats and millet. J. Agr. Sci. 18: 634. Halnan, E. T. 1937. Digestibility of wheat oifals. Jour. Agr. Sci. 27: 126-142. Moon, F. E. and B. Thomas. 1937. The digestion of huskless oats by poultry. Agr. Sci. 27: 458-464. - Shirley, R. L., and A. H. Vanlandingham. 1939. Determination of uric acid in‘ mixed excrements of birds. Jou_r. Ind. Eng. Chem. Anal. Ed. 11: 381.