§ LIBRARY , Ij1A & M COLLEGE, C A M p U S _ R6l-1136—6m EXAS AGRICULTURAL EXPERIMENT STATION A. B. CONNERY, DIRECTOR COLLEGE STATION, BRAZOS COUNTY, TEXAS ULLETIN NO. 536 FEBRUARY, 1937 DIVISION OF CHEMISTRY AND DIVISION OF DAIRY HUSBANDRY _ IIIBRIARY liflillllrilllachaicalemnnw Mfifiwintws. I UTILIZATION OF VITAMIN A BY DAIRY cows AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS T. O. WALTON, President The vitamin A potency of butter from the 9 Jersey cows studied decreased from 43 and 62 Sherman-Munsell units per gram at the beginning of the experiment to 4 units per gram for cows receiving 7,000 units per day, to 12 units for cows receiving 170,000 units per day, and to 10 units for cows receiving 340,000 units per day at the end of seventeen weeks. The carotene decreased from 16.7, 9.7, and 9.8 parts per million in the beginning to 0.4, 3.9, and 3.6 parts per million respectively for the three levels of vitamin A consumption. The apparent recovery of the vitamin A potency in the butter varied from 213 to 2.4 per cent of that in the feed. The apparent percentage recovered was greatest at the beginning of the experi- ment and greatest also for the cows receiving the least amo-unt of vitamin A in the feed. The high percentage of vitamin A appar- ently recovered was due to the fact that some of it came from that stored in the body of the cow. If correction is made for the vitamin A potency stored by the cows, the average utilization was 2.38 to 2.67% for the five periods. The vitamin A potency of the butterfat from some of the cows was higher than that of others fed on the same feed for the same period of time. Some cows appear to have a greater power than others to secrete vitamin A and carotene into the butter. Sorghum preserved with mineral acids (A. I. V. silage) was low in carotene and had only a slight efiect upon the carotene and vitamin A in the butter when fed to cows previously depleted. When two cows were depleted by feed low in vitamin A and then placed upon pasture, the vitamin A potency of the butter increased from 12 units per gram to 40 or 50 units per gram within three days. When other depleted cows were placed upon pasture, there was likewise a rapid increase in the vitamin A potency of the butter. The carotene in the butterfat reached the maximum of 13.96 parts per million with one cow in 28 days and a maximum of 19.06 with the other cow in 14 days followed by a decrease with both cows. There was a rapid increase in spectro-vitamin A, which reached a maximum in fourteen days. One cow apparently had a greater capacity to secrete vitamin A and carotene in the butterfat than the other. The vitamin A potency of the butter of the cows on pasture was high, a maximum of 72 Sherman-Munsell units with one cow and 101 units for the other as calculated from the carotene and spectro-vitamin A. The vitamin A potency of the butter is closely related to the vitamin A potency of the feed and the period of time the cow has been receiving it. It is calculated from this work and that of others that from 750,000 to 1,400,000 Sherman-Munsell units are required per cow per day to produce butterfat containing from 65 to 95 Sherman-Munsell units per gram, the amount found in very good butter. CONTENTS Page Introduction 5‘ Utilization of vitamin A by dairy cowso __________ __ 5 Method of procedure 6 Carotene content of the butterfat 9_ Vitamin A potency of the butterfat 10 Relation of quantities of vitamin A potency in the feed to quantities in "the butterfat, A 11 Units of vitamin A required in the feed over maintenance requirements for a unit of vitamin A in the butter _________________ __ 14 Individual variations in the vitamin A potency of butterfat ________ _- 16 Rate of utilization of vitamin A potency (carotene)? ___________________ __ 19 Summary 24 References 26 BULLETIN NO. 536 FEBRUARY, 1937 UTILIZATION OF VITAMIN A BY DAIRY COWS G. S. Fraps, Division of Chemistry; O. C. Copeland, Division of Dairy Husbandry; Ray Treichler, and A. R. Kemmerer, I Division of Chemistry. It is now known that the vitamin A potency of butter is closely related to the vitamin potency of the diet of the cow. 1t has recently been shown by us (5) that cows which had access to pasture before but not during lactation produced butter high in vitamin A at first, but that the vitamin A potency of the butterfat decreased during the period of lactation. The vitamin A potency of the butter depended not only upon the vitamin A potency of the feed but upon the previous feed of the cow before the lactation started or during lactation and the length of time the cow had been receiving the feed at the time the sample of butter was taken. The decrease in vitamin A potency was greater when the feed was low in vitamin A than it was when the feed was high in vitamin A, but a decrease occurred even with feed high in vitamin A. Cows which were in the later periods of lactation and were producing butter very low in vitamin A-potency, after being placed on pasture produced butterfat high in vitamin A potency (5). The decrease therefore was due to insufficient vitamin A potency in the feed and not to the stage of lactation. We have also shown (15) that butterfat naturally of deep yellow color was likely to contain more vitamin A potency than light- colored butter. Other workers (11) have also correlated the yellow color or carotene of butterfat with its vitamin A content. Additional refer- ences may be found in previous publications (15). Cows in general secure their vitamin A potency from the carotene in grasses and fodders and from cryptoxanthine and carotene in yellow corn. Cows receive vitamin A as such only if they are fed cod liver oil, or a concentrate of fish liver oil or certain other fish oils. The carotene and cryptoxanthine in the feed is partly converted into vitamin A since both vitamin A and carotene may be found in the blood, and liver, and in the butterfat of animals receiving only carotene as a source of vitamin A. Baumann et al (2) calculated that on a low carotene ration 1.6 per cent of the vitamin A potency and 1.1 per cent of the carotene ingested was secreted into the milk, and that on a high carotene ration only 1.3% of the vitamin A potency and 0.4 per cent of the carotene fed was secreted. Russell (13) reported that 2.5 to 3.4% of the vitamin A value of dried alfalfa and corn silage usually appeared in the milk on a daily intake of 1,213,500 to 946,700 U. S. P. 1934 units per cow. Peterson et al (12) (stated that only about 2% of the carotene appeared in the butterfat when the cow was fed high amounts, 298 to 561 mg. of carotene per day, of A. I. V. alfalfa silage. These results indicate the apparent utilization at definite periods and do not allow for the vitamin A stored in the body of the animal. 6 BULLETIN NO. 536, TEXAS AGRICULTURAL EXPERIMENT STATION It has been shown in Texas Bulletin 495 (5) that 116,000 Sherman- Munsell units of vitamin A potency per day in about 7 pounds of yellow corn and 6 pounds of alfalfa leaf meal was not sufficient to maintain the vitamin A potency of the butterfat. In this work, on an average, one unit of vitamin A potency in the butter required approximately 11 units in the feed over maintenance requirements. As the experiment we con- ducted was made with only three cows and there may have been dif- ferences in the quantities of vitamin A potency stored by the_c0ws, a considerable latitude for error must be allowed on account of the neces- sary corrections for storage and maintenance requirements. It was con- sidered desirable to make a similar experiment with a larger number of cows at higher levels of vitamin A potency. Experiments were also made to ascertain the time required for carotene fed to the cow to appear in the butterfat and be converted into vitamin A. Method of Procedure In the experiments reported here on the utilization of vitamin A potency of feeds, nine Jersey cows, divided into three equal groups, were used. The cows had been fed alike upon the _usual ration, including pasturage, given cows before calving. Five days after the cows had calved, they were placed upon the experimental ration. All the cows received daily about 20 pounds of cottonseed hulls and 15 pounds of beet pulp. Block salt and tap water were also provided. The grain mixture fed the cows consisted of 6O per cent yellow corn, 27 per cent cottonseed meal, 10 per cent wheat bran, 2 per cent pulverized oyster shell, and 1 per cent salt, made available at the rate of approximately % pounds for each pound of milk per cow daily. One group of three cows received vitamin A potency in yellow corn alone. The second group of three cows received three pounds of heat-dried alfalfa leaf meal in addition to the yellow corn, and a third group of three cows received six pounds of alfalfa leaf meal in addition to the yellow corn. The vitamin A potency was provided by cryptoxanthine and carotene in the yellow corn and the carotene in the alfalfa leaf meal. The first sample of butter was collected at the beginning of the experiment five days after calving, the second at the end of seven days, and the other samples at the ends of periods of twenty-eight days. The dates of calving and the dates of collecting samples of butter are given in Table 1. The vitamin A potency of the feed was determined by means of rats by the modified Sherman-Munsell procedure already described in detail (4,14). The details of the estimations are given in Table 2. Since there was a decrease in the vitamin A potency of the feed during storage as shown in Table 2 this decrease was considered to be regular at the rate of 7% a month (5,141). The vitamin A assumed to be present in the feed during the various periods is given in Table 3.‘ The samples of the butter were melted, and the fat was separated and kept in an electric refrigerator. As it was not possible by means of rats to determine the UTILIZATION OF VITAMIN A BY DAIRY COWS 7 TABLE 1. Age, dates of calving, and dates samples of butter were collected \ , Cow number . . . . . . . . . . . . . . . . . . .. 192 356 370 65 I 363 l 376 74- 301 364 Age of cow, in years and months. . 8-10 4-0 3-6 5-4 I 3-8 3-2 3-6 8-2 3-8 Date of calving, 1934 . . . . . . . . . . .. 8/27 8/8 9/24 7/30 7/24 _9/3 9/13 9/9 7/17 First sample of butter collected, 1934 . . . . . . . . . . . . . . . . . . . . . . . 9 1 8/13 9/29 8/4 7/29 9/8 9/18 9/14 7/22 Second sample collected, 1934... .. 9/8 8/20 10/6 8/11 8/5 9/15 9 25 9/21 7/29 Third sample collected, 1934 . . . . . . 10/6 9/17 11/3 9/8 9/2 10/13 10/23 10/19 8/26 Fourth sample, 1934 . . . . . . . . . . . .. 11/3 10/15 . . . . . .. 10/6 9/30 11/10 11/20 11/16 9/23 Fifth sample, 1934 . . . . . . . . . . . . . .. 12/1 11/12 12/29 11/3 10/2s 12/s 12/1s 12/14 10/21 Sixth sample, 1934-35 . . . . . . . . . . .. 12/29 1/26/35 12/1/34 .....l1/s/ss 1/15 1/11 11/18/34 TABLE 2. Details of estimation of vitamin A potency of feeds in Sherman- Munsell units per gram Average Units / Labora- Grams Number Number gain vitamin tory Feed tested Date fed of rats of rats per rat A Number sampled per day at be- at end in potency ginning 8 weeks per gram 40626 Shelled yellow corn . . . . . . . . . . . . 8/ 30/ 34 . 15 6 1 ——33 . . . . . . . . .20 6 3 —-20 .30 6 3 3 . . . . . . . . I .40 6 s 2s 2 . 6 T 40627 Heat dried alfalfa leaf meal. . . . . 8/30/34 .0066 6 2 23 143 .01 6 4 44 . . . . . . .. .0133 6 5 46 . . . . . . . . g .02 6 6 40 . . . . . . . . V .03 6 6 63 . . . . . . .. ; .04 6 6 71 . . . . . . . . 5 .05 6 s 6s . . . . . . . . 41110 Shelled yellow corn . . . . . . . . . . . . 11/16/34 .15 6 1 —9 . . . . . . . . .20 6 2 2 . . . . . . . . . 3O 6 2 35 . . . . . . . . .50 6 6 28 2 1 41111 Heat dried alfalfa leaf meal. . . . . 11/16/34 .0066 g 0 -—-4 . . . . . . . . .01 2 -— . . . . . . . . . 0133 6 4 39 85 . f. TABLE 3. Assumed vitamin A potency of feed by months, in Sherman-Munsell rat units per gram g j. - . é Yellow corn Alfalfa leaf meal 1 l T August . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3.4 151 i September . . . . . . . . . . . . . . .' . . . . . . . . . . . . . . . . . . . . . . 3.2 141 October . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3.0 131 i November . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.8 122 g December . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.6 114 §' January . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 106 "- February . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 99 l vitamin A potency of all the individual samples of butter, the three .,samples from the three cows on the same feed were combined in one sample for each period and the vitamin A potency in this mixture was estimated by means of rats as previously described (4,141). Details of githis estimation are given in Table 4. A summary of the vitamin A potency of the butterfat in Sherman-Munsell units per gram is given ‘in Table 5. 8 BULLETIN NO. 536, TEXAS AGRICULTURAL EXPERIMENT STATION TABLE 4. Details of estimation of vitamin A potency of butterfat Average Vitamin Labora- Alfalfa Butter- Number Number gain A units tory Description fed fat fed of rats of rats per rat to one Number pounds per day at be- at end in 8 wks. gram fat grams ginning grams 40925 First samples, beginning of test 5 days after calv- ing . . . . . . . . . . . . . . . . . . . 3 .02 6 4 22 50 .033 7 5 49 40930 " " " 0 .02 6 5 18 43 .033 6 6 35 40952 " " " 6 .02 6 3 34 62 .033 6 5 65 40954 Second sample, 1 week _ on fee . . . . . . . . . . . . . . .. 3 .026 6 5 17 33 .04 6 4 55 40955 " ” " 6 .026 6 3 32 43 .04 6 5 64 40961 " " " O .026 6 4 14 33 .04 6 3 44 41132 Third sample, 5 weeks on feed . . . . . . . . . . . . . . . . 6 .033 6 1 22 28 .05 6 5 50 41134 " " " .04 6 0 -—- 3 .05 6 S 23 2O .07 6 5 53 41139 " " " _ 05 6 2 16 0 .07 6 2 25 14 . 1 6 4 39 41218 Fourth sample, 9 weeks on feed . . . . . . . . . . . . . . . . 6 .05 6 4 33 23 .07 6 3 41 41231 " ” " 3 .05 6 4 36 25 .07 6 4 69 . 1 6 3 83 41256 " " " O . 1 6 S 3O 1O . 133 6 4 35 41265 Fifth sample, 12 weeks on feed . . . . . . . . . . . . . . . . 3 .07 6 5 23 14 . 1 6 4 29 . 133 6 3 34 .05 6 4 24 20 41282 " " " 6 .07 6 5 35 . 1 6 4 57 41299 " " " 0 .1 6 1 11 . 15 6 3 34 7 .2 6 4 51 41362 Sixth sample, 17 weeks on feed . . . . . . . . . . . . . . . . 3 - .07 6 1 26 . 1 6 3 41 12 .133 6 4 42 41384 " " " o .1 6 1 ~25 . 15 6 1 9 .2 6 1 ——5 4 .3 6 4 58 41385 " " " 6 .07 6 3 9 \ . 1 12 S 23 10 . 13 6 4 34 UTILIZATION OF VITAMIN A BY DAIRY COWS 9 Carotene Content of the Butterfat The quantity of carotene in the butterfat, like that of vitamin A, in addition to the breed of the cow (2), depends upon the quantity of caro- tene fed and the length of time it has been fed. As shown in Texas Bulletin 513 (15), butter high in vitamin A is likely to be naturally highly colored but all colored butter is not high in vitamin A. Light colored butter is likely to be low in vitamin A. Similar results were secured by Meigs (11). The carotene in the butterfat was determined by the spectrophoto- metric method already described (l5). Miss Mary Anna Grimes of the Division of Rural Home Research made the spectrophotometric readings. A summary of the results is given in Table 6, together with similar results obtained in previous experiments (5). The periods of time in the earlier work are not exactly the same as in the work here reported. TABLE 5. Vitamin A potency of butterfat in Sherman-Munsell units per gram Experiments in 1935 Experiments in 1933 End Weeks Series of in 3 6 White Yellow Yellow 3 lbs. 6 lbs. period experi- Yellow pounds pounds corn corn corn alfalfa alfalfa ment corn alfalfa alfalfa Cow Cow Cow Cow Cow daily daily 59 61 196 322 329 1 0 0 43 50 62 40 28 2S 70 33 2 1 1 33 33 43 25 17 — —— —— 3 2 5 14 2O 28 8 12 8 14 2O 4 3 9 10 25 23 8 7 8 14 12 5 4 13 7 14 20 17 6 — —— — 6 5 17 4 12 1O 7 5 4 1O 1 1 Approximate units fed per day . . . . . . . . 7,000 170,000 340,000 0 17,000 8,400 60,000 116,000 TABLE 5A. Vitamin A potency of butterfat in International units per gram Experiments in 1935 Experiments in 1933 End Weeks Series of in 3 6 White Yellow Yellow 3 lbs. 6 lbs. period experi- Yellow pounds pounds corn corn corn alfalfa alfalfa ment corn alfalfa alfalfa Cow Cow Cow Cow Cow daily daily 59 61 196 322 329 1 0 O 52 60 74 48 34 30 84 40 2 1 1 4O 40 52 3O 2O -—- ——~ —- 3 2 5 17 24 34 1O 14 10 17 24 4 3 9 12 3O 28 1O 8 1O 17 14 5 4 13 8 17 24 13 7 -— ~—— ——— 6 5 ' 17 5 14 12 8 6 5 12 13 Approximate units fed per day . . . . . . . . 8,400 204,000 408,000 0 20,400 10,080 72,000 139,200 As in the previous experiments, the amount of carotene in the butter decreased during the period of feeding. The decrease is greater with the yellow corn alone than with the corn and alfalfa meal. The amount of carotene in the butter from the cows receiving the six pounds of 1.. a a R A R Y Agtiwliural 8K htaziiamical teillege of Texas Ccliege Statinn, Texas. 10 BULLETIN NO. 536, TEXAS AGRICULTURAL EXPERIMENT STATION alfalfa leaf meal was higher at "the end of 9 and 13 weeks than from the cows receiving 3 pounds of alfalfa leaf meal, but it was lower at the end of 13 and 17 weeks. Apparently the larger quantity of carotene in 6 pounds of alfalfa leaf meal had little more effect upon that in the butter than the smaller amount. The butterfat from the cow fed 116,000 units daily in 1933 was higher in carotene than the average of 3 cows receiving about 340,000 units daily in 1935 in 6 pounds of alfalfa meal. This difference may have been due to the individuality of the cow. Baumann et al (2) have shown that Guernsey cows on an average give butter containing more carotene than do Jersey or several other breeds of cows, but since the vitamin A is lower where the carotene is higher, the butterfat does not differ much in vitamin A potency. TABLE 6. Carotene in butterfat, in parts per million Experiments 1935 Experiments 1933 , Weeks _ on Experiment Yellow Alfalfa Alfalfa White Yellow Yellow Alfalfa Alfalfa corn 3 lbs. 6 lbs. corn corn corn 3 lbs. 6 lbs. 0 16.7 9.7 9.8 9.2 10.7 12 8 12.2 13 6 1 7.9 10.5 9.5 5.9 5.6 . . . . . . . . . . . . . .. 5 2.0 5.6 5.1 0.7 2.0 3.4 3.6 8.0 9 1.1 4.1 4.5 0.4_ 1.0 1.4 2.4 7.1 13 0.8 3.5 4.9 0.3 0.6 . . . . . . . . . . . . . .. 17 0.4 3.9 3.6 0.2 0.3 1 2.4 6.0 Vitamin A Potency of the Butterfat The data from the estimation, by means of rats, of vitamin A in the butterfat at various intervals are given in Table 5. For comparative purposes, the vitamin A found in similar previous work (Bulletin 495) is also stated. The periods of time are not exactly the same for the different experiments. The vitamin A potency decreased more during the first week. After the first 4 or 5 weeks, the vitamin A potency had materially decreased. The quantities present in the butterfat from the cows fed yellow corn, in three experiments, were comparatively close at the same periods of feeding. The vitamin A in the butterfat from the cows fed alfalfa meal was higher at the beginning in the 1935 experiment than in the 1933 (5) experiments. This is accounted for by the fact that the cows received much more vitamin A potency in 1935 than in 1933. The alfalfa leaf meal fed in 1934-5 contained 3 times as much vitamin A potency as that fed in 1933. This difference is reflected at first in the vitamin A po- tency of the butterfat, but it is not apparent at the end of 17 weeks. In spite of discrepancies to be expected in experimental work of this kind it is interesting that there is a remarkable similarity in the vitamin A potency of the butterfat from cows fed similar quantities of vitamin A potency, at corresponding periods of feeding, toward the end of the experiment. UTILIZATION OF VITAMIN A. BY DAIRY COWS Relation of Quantities of Vitamin A Potency in the Feed to Quantities in the Butter-fat The quantities of feed consumed and of milk and fat produced are The calculated Sherman-Munsell units of vitamin A given in Table 7. 11 TABLE 7. Consumption of feed and production of milk and butterfat, average per day Total Yellow Alfalfa Milk Fat Fat Periods Dates of Periods grain corn meal pounds per cent pounds pounds pounds pounds Cow No. 192—Fed on Yellow Corn. First— Sept. 1-7, 1934, incl . . . . . . . . . . 10.00 6.00 0 27.80 2 .45 .68 Sec0nd—- Sept. S-Oct’. 5, 1934, incl. . . . . 8 .93 5 . 36 0 25 . 29 3 . 25 .82 Third—- Oct. 6-Nov. 2, 1934, incl . . . . . . 8.93 5.36 0 19.35 3. 7 .72 Fourth- Nov. 3-30, 1934, incl . . . . . . . . . 8.00 4.80 0 16.00 3.55 .57 Fifth—- Dec. 1-28, 1934, incl . . . . . . . . . . 8.00 4.80 0 14.50 3.8 .55 Cow No. 356—Fed on Yellow Corn. First— Aug. 13-19, 1934, incl . . . . . . .. 10.29 6.17 0 28.54 4.2 1.20 Second— Aug. 20-Sept. 16, 1934, incl.. . 12.00 7.20 0 29.83 4.8 1.43 Third— Sept. 17-Oct. 14, 1934, incl.. . . 11 .57 6.94 0 ' 24.30 4.4 1 ,07 Fourth- Oct. 15-Nov. 11, 1934, incl.. .. 11.21 6.73 0 19.57 6.8 1,33 Last period missed on account of cow _ being sick. .. Cow No. 370—Fed on Yellow Corn. First- Sept. 29-Oct. 5, 1934, incl.. . . . 6. 29 3. 77 0 25 .03 4. 2 1 .05 ' Second——— Oct. 6-Nov. 2, 1934, incl . . . . .. 6.14 3.69 0 24.97 4.6 1.15 Third— Nov. 3-30, 1934, incl . . . . . . . . . 7 .00 4.20 0 21 .49 4.8 1 .03 F0urth— Dec. 1-28, 1934, incl.. . . . . . . . . 8.00 4.80 0 18.64 5.3 .99 Fifth—— Dec. 29, 1934—Jan. 25, 1935, p in . . . . . . . . . . . . . . . . . . . . .. 7.79 4.67 0 19.03 5.1 _97 3 Cow No. 65——Fed on 3# Alfalfa Meal and f. Yellow Corn daily. First—- Aug. 4-10, 1934, incl . . . . . . . . . 5 .93 3.56 3.00 35 .51 4.0 1 .42 Sec0nd——- Aug. ll-Sept. 7, 1934, incl. . . . 10. 2S 6.15 3.00 34. 79 3.95 1 .37 Third— Sept. 8-Oct. 5, 1934, incl . . . . . . 11.00 6.60 3.00 32.15 4.05 1,30 Fourth— Oct. 6-Nov. 2, 1934, incl . . . . . . 11.00 6. 60 3 . 00 29 .40 4. 35 1 . 28 Fifth——- NOV. 3-30, 1934, incl . . . . . . . .. 11.00 6.60 3.00 27.54 4. 1 1 . 13 ‘I Cow No. 363——Fed on Yellow Corn and ‘ 3# Alfalfa Meal daily. ' First—- July 29-Aug. 4, 1934, incl.. . . . 8.29 4.97 3.00 25.40 4.0 1.02 Second— Aug. S-Sept. 1, 1934, incl.. . . . 10.07 6.04 3.00 28.44 4.4 1.25 Third-— Sept. 2-29, 1934, incl . . . . . . . . . 12 .00 7.20 3.00 25.40 4.4 1.12 L3‘ ' Fourth—- Sept. 30-Oct. 27, 1934, incl.. . . 10.07 6.04 3.00 20.50 4.5 .92 " Fifth— Last period missed on ac- , count of cow being sick. {Cow No. 376——Fed on Yellow Corn and 3# Alfalfa Meal daily. First—— Sept. 8-14, 1934, incl . . . . . . . . . 5.49 3.29 2.40 17.43 3.85 .67 Sec0nd— Sept. 15-Oct. 12, 1934, incl.. . . 6.30 3.78 2.66 22.24 4.4 .93 Third—- Oct. 13-Nov. 9, 1934, incl.. . . . 6.64 3.99 3.00 20.61 4.85 1.00 Fourth— Nov. 10-Dec. 7, 1934, incl.. . . . 7 .00 4. 20 2 . 45 17 .97 5 . 2 .93 Fifth- Dec. 8, 1934-]an. 4, 1935, incl . . . . . . . . . . . . . . . . . . . . .. 8.00 4.80 3.00 17.84 5.1 .91 Cow No. 74—Fed on Yellow Corn and 6# Alfalfa Meal daily. First— Sept. 18-24, 1934, incl . . . . . . . . 4.03 2 . 41 4.03 22.13 3 . 6 _ 80 Second—— Sept. 25-Oct. 22, 1934, incl.. . . 5.72 3.43 5.58 24. 79 4.0 .99 " Third—- Oct. 23-Nov. 19, 1934, incl.. .. 7.36 4.41 6.00 23.66 4.4 1,04 _; a F0urth—— Nov. 20-Dec. 17, 1934, incl. .. 7.00 4.20 5.04 21.40 4.55 _97 7 Fifth— Dec. 18, 1934-]an. 14, 1935, A incl . . . . . . . . . . . . . . . . . . . . .. 7.79 4.67 5.86 23.61 4.25 1,00 §;,Cow No. 301-——Fed on Yellow Corn and i 6# Alfalfa meal daily. First— Sept. 14-20, 1934, incl . . . . . . .. 6.00 3.60 6.00 33.69 4.1 1.33 Sec0nd— Sept. 21-Oct. 18, 1934, incl. . . 7.93 4.76 6.00 35.53 4.3 1.53 sf» Third— Oct. 19-Dec. 15, 1934, incl. . . . 9.25 5.55 6.00 32.15 4.7 1.51 ’ Fourth-— Nov. 16-Dec. 13, 1934, incl. . . 8.00 4.80 6.00 24.84 5.05 1 .25 Fifth—- Dec. 14, 1934-Jan. 10, 1935, incl . . . . . . . . . . . . . . . . . . . . .. 8.00 4.80 6.00 20.80 5.1 1.06 12 BULLETIN NO. 536, TEXAS AGRICULTURAL EXPERIMENT STATION TABLE 7. Consumption of feed and production of milk and butterfat, average per day—Continued Total Yellow Alfalfa Milk Fat Fat Periods Dates of Periods grain corn meal pounds per cent pounds poundsi pounds pounds Cow No. 364—Fed on Yellow Corn and 6# Alfalfa Meal daily. First— July 22-28. 1934, incl . . . . . . . . . 7.43 4.46 6.00 25.90 4.6 1. 19 Second—- July 29-Aug. 25, 1934. incl.. .. 11.57 6.94 6.00 28.93 4.8 1.39 Third—- Aug. 26-Sept. 22. 1934, incl. .. 12.00 7.20 6.00 27.40 5.0 1.37 Fourth—— Sept. 23-Oct. 20. 1934. incl. . . 9.71 5.83 6.00 22.39 5.85 1.31 Fifth- Oct. 21-Nov. 17, 1934, incl.. .. 10.00 6.00 6.00 18.66 6.5 1.21 eaten in the corn and alfalfa and secreted in the butterfat are given in It is seen in Table 8 that during the first period of seven days and the second period of 28 days, the cows receiving vitamin A potency in yellow corn alone produced appreciably more vitamin A in the butter Table 8. than was present in the feed. TABLE 8. Vitamin A potency in Sherman-Munsell rat units eaten daily and secreted in butterfat Vitamin Vitamin Vitamm Vitamin A in A in Date of A eaten butter butter- Period eaten in Units fat in alfalfa per Units corn meal gram per day No alfalfa. First period, 7 days Cow 192 . . . . . . . . . . . . . 9-1-34 to 9-7-34. incl . . . . . . . 8 .710 0 . . . . . . . . . . 356 . . . . . . . . . . . .. 8-13-34 to 8-19-34, incl.. . .. 9 .517 0 . . . . . . . . .. 370 . . . . . . . . . . . . . 9-29-34 to 10-5-34. incl.. . . . 5 .472 0 . . . . . . . . . . Average per cow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 ,900 0 38 16 .821 Second Period. 28 days. Cow 192 . . . . . . . . . . . . . 9-8-34 to 10-5-34, incl.. . . . . 7 .779 0 . . . . . . . . . . 356 . . . . . . . . . . . . . 8-20-34 to 9-16-34, incl.. . . . 10 .451 0 . . . . . . . . . . 370 . . . . . . . . . . . . . 10-6-34 to 11-2-34, incl.. . . . 5 .022 0 . . . . . . . . . . Average per cow. . .. . . . . . . . . . . . . . . . . . . . . . . . . .. 7 .751 0 23.5 12 .087 Third Period. 28 days. Cow 192 . . . . . . . . . . . .. 10-6-34 to 11-2-34. incl.. . . . 7 .293 0 . . . . . . . . . . 356 . . . . . . . . . . . . . 9-17-34 to 10-14-34, incl. . . . 10 .074 0 . . . . . . . . . . 370 . . . . . . . . . . . . . 11-3-34 to 11-30-34. incl. . . . S .334 0 . . . . . . . . . . Average per cow... . . . . . . . . . . . . . . . . . . . . . . . . . .. 7 .567 0 12 5 .116 Fourth Period, 28 days. Cow 192 . . . . . . . . . . . . . 11-3-34 to 11-30-34, incl.. . . 6 .096 0 . . . . . . . . . . 356 . . . . . . . . . . . . . 10-15-34 to 11-11-34. incl.. . 8 .548 0 . . . . . . . . . . 370 . . . . . . . . . . . . . 12-1-34 to 12-28-34. incl.. . . 5 .660 0 . . . . . . . . .. Average per cow... . . . . . . . . . . . . . . . . . . . . . . . . . .. 6 .768 0 8.5 3 .715 Fifth Period, 28 days. Cow 192 . . . . . . . . . . . . . 12-1-34 to 12-28-34. incl. . . . S .660 O . . . . . . . . . . 356 Last period missed on ac- count of cow being sick. 370 . . . . . . . . . . . . . 12-29-34 to l-25-35. incl.. . . 5 .083 0 . . . . . . . . .. Average per cow... . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 .372 0 5.5 1.895 3 pounds alfalfa daily. First Period. Cow 65 . . . . . . . . . . . .. 8-4-34 to 8-10134, incl.. . . . . 5 .491 205 .511 . . . . . . . . . . 363 . . . . . . . . . . . . . 7-29-34 to 8-4-34, incl . . . . . . 7 .664 205 .511 . . . . . . . . .. 376 . . . . . . . . . . . . . 9-8-34 to 9-14-34, incl . . . . . . 4 .774 153 .549 . . . . . . . . .. Average per cow . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 .976 188 .190 41.5 19 .519 UTILIZATION OF VITAMIN A BY DAIRY COWS 13 TABLE 8. Vitamin A potency in Sherman-Munsell rat units eaten daily and secreted in butterfat—-Continued Vitamin Vitarnin Vitamin Vitamin A A m A in Date of A eaten butter butter- Period eaten in Units fat in alfalfa per Units corn meal gram per day Second Period. Cow 65 . . . . . . . . . . . . . 8-11-34 to 9-7-34, incl . . . . . . 9 .486 205 .511 . . . . . . . . . . 363.. . 8-5-34 to 9-1-34. incl . . . . . . . 9 .316 205 .511 . . . . . . . . . . 376 . . . . . . . . . . . . . 9-15-34 to 10-12-34, incl. . . . 5 .488 158 .117 . . . . . . . . . . Average per cow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 .097 189 .713 26.5 14 .425 Third Period. Cow 65 . . . . . . . . . . . . . 9-8-34 to 10-5-34. incl . . . . . . 9 .581 191 .901 . . . . . . . . . . 363 . . . . . . . . . . . . . 9-2-34 to 9-29-34, incl.. . . . . 10 .451 191 .901 . . . . . . . . . . 376 . . . . . . . . . . . . . 10-13-34 to 11-9-34, incl. . . . 5 .430 178 .291 . . . . . . . . . . Average per cow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 .487 187 .364 22 .5 11 .640 Fourth Period. Cow 65 . . . . . . . . . . . . . 10-6-34 to 11-2-34, incl.. . . . 8 .982 178 .291 . . . . . . . . . . 3 . . . . . . . . . . . . . 9-30-34 to 10-27-34. incl. . . . 8 .220 178.291 . . . . . . . . . . 376 . . . . . . . . . . . . . 11-10-34 to 12-7-34, incl. . . . 5 .334 135 .542 . . . . . . . . . . Average per cow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 .512 164 .041 19.5 9 .230 Fifth Period. Cow 65 . . . . . . . . . . . . . 11-3-34 to 11-30-34, incl. . . . 8 .383 166 .042 . . . . . . . . . . 3 . . . . . . . . . . . . . Last period missed on ac- count of cow being sick. 376 . . . . . . . . . . . . . 12-8-34 to 1-4-35. incl . . . . .. 5 .660 155 .154 . . . . . . . . Average per cow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 .022 160 .598 13.0 6 .019 6 pounds alfalfa daily. First Period. Cow 74 . . . . . . . . . . . . . 9-18-34 to 9-24-34, incl. . . . . 3 .498 257 .748 . . . . . . . . . . 301 . . . . . . . . . . . . . 9-14-34 to 9-20-34. incl. . . . . 5 .226 383 .802 . . . . . . . . . . 364 . . . . . . . . . . . . . 7-22-34 to 7-28-34. incl. . . . . 6 .878 411 .022 . . . . . . . . . . Average per cow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 .201 350 .857 52.5 26 .758 Second Period. Cow 74 . . . . . . . . . . . . . 9-25-34 to 10-22-34. incl. . . . 4 .668 331 .561 . . . . . . . . . . 301 . . . . . . . . . . . . . 9-21-34 to 10-18-34, incl.. . . 6 .477 356 .582 . . . . . . . . . . 364 . . . . . . . . ; . . . . 7-29-34 to 8-25-34. incl.. . . . 10 .703 411 .022 . . . . . . . . . . Average per cow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 .283 366 .388 35.5 20 .992 Third Period. Cow 74 . . . . . . . . . . . . . 10-23-34 to 11-19-34. incl. . . 6 .000 332 .084 . . . . . . . . . . 301 . . . . . . . . . . . . . 10-19-34 to 11-15-34. incl. .. 7 .551 332 .084 . . . . . . . . . . 364 . . . . . . . . . . . . . 8-26-34 to 9-22-34. incl. . . . 10 .451 383 .802 . . . . . . . . . . Average per cow. . .. . . . .' . . . . . . . . . . . . . . . . . . . . .. 8 .001 349 .323 25.5 15 .113 Fourth Period. Cow 74 . . . . . . . . . . . . . 11-20-34 to 12-17-34. incl.. . 5 .334 260 .604 . . . . . . . . . . 301 . . . . . . . . . . . . . 11-16-34 to 12-13-34. incl. . . 6 .096 310 .308 . . . . . . . . . . 364 . . . . . . . . . . . . . 9-23-34 to 10-20-34, incl. . . . 7 .932 356 .582 . . . . . . . . . . Average per cow. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . 6 .454 309 .165 21.5 11 .474 Fifth Period. Cow 74 . . . . . . . . . . . .. 12-18-34 to 1-14-35.inc1... . 5 .083 281.748 . . . . . . . . . . 301 . . . . . . . . . . . . . 12-14-34 to 1-10-35.inc1. . . . 5 .225 288 .532 . . . . . . . . . . 364 . . . . . . . . . . . . . 10-21-34 t0 11-17-34. incl. . . 8 .166 332 .084 . . . . . . . . . . Average per cow... . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 .158 300 .788 15.0 ' 7 .420 A comparison of the average consumption of vitamin A potency in the feed and its recovery in the butterfat are given in Table 9. The apparent autilization varies from 212.9 to 2.4 per cent, depending on the quantity . of vitamin A potency of the feed and the period of time after the experi- _ment had begun~—that is, the extent of depletion of the cow. The . apparent percentage recovered in the fat is greatest with the cows re- > i» n 14 BULLETIN NO. 536, TEXAS AGRICULTURAL EXPERIMENT STATION ceiving the least amount of vitamin A in the feed. This is due to the use of larger proportions of the carotene and vitamin A stored in the body by the cow receiving feed low in carotene. Similar results were secured in previous work (5). As has already been pointed out, these figures represent only the apparent utilization of the vitamin A potency, and not its actual utiliza- tion, since some of the vitamin A in the butter came from that stored in the body of the cow. The relative quantity of the stored vitamin A potency which was secreted in the butter is greatest when the least amount of vitamin A potency is present in the feed. For this reason the apparent utilization is highest when the least vitamin A potency is fed. It is of course possible that the cow may utilize small quantities of vitamin A better than large quantities, and the results presented in the bulletin seem to indicate that this is probable. TABLE 9. Vitamin A potency in feed, and in butter, and apparent percentage recovered Total Vitamin A Vitamin A Period total corn in butter- Recovered and alfalfa fat aver- average average per age per per cent day per cow day per cow ‘ Series 0. No alfalfa . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1 7,900 16,821 212.9 2 7,751 12,087 155.9 3 7,567 5,116 67.6 4 6,768 3,715 54.9 5 5,372 1,895 35.3 Series 3. ' 3 pounds of alfalfa . . . . . . . . . . . . . . . . . . . . . 1 194,166 19,519 10.1 2 197 ,81O 14,425 7.3 3 195,851 11,640 5.9 4 171 ,553 9 ,23O 5.4 5 167,620 6 .019 3.6 Series 6. 6 pounds of alfalfa . . . . . . . . . . . . . . . . . . . . 1 356,058 26 .758 7.5 2 373 ,671 20,992 5.6 3 357,324 15,113 4.2 4 315,619 11,474 3.6 5 306 ,946 7 ,420 2 .4 Units of Vitamin A Required in the Feed over Maintenance Requirements for a Unit of Vitamin A in the Butter The fact that a reserve of vitamin A is stored in the body of the animal makes the estimation of the utilization of vitamin A by the animal somewhat complicated. When two groups of animals are fed at two levels of vitamin A, the vitamin A in the butter produced during a definite period is due to the effects of that in the feed plus that in the bodies. If it is assumed that the vitamin A stored in the bodies of the cows is the same in both groups, then the difference in the quantity of vitamin A in the butters is due to the difference in vitamin A in the feed. UTILIZATION OF VITAMIN A BY DAIRY COWS 15 Subtracting one from the other cancels out the efiects of vitamin A stored, if the stores are assumed to be the same. This assumption is better justified if a large number of animals is used, than if the number is small, since the stores in individual animals vary, while in large groups these individual differences are averaged out. In previous work it was calculated, by the procedure mentioned above but at lower levels of feeding, that 6 to 13 units of vitamin A are re- quired in the feed for one unit in the butterfat. Only one cow was used in each group; for this reason the results are uncertain. The levels fed were about 8,400, 60.000, and 116,000 Sherman-Munsell rat units per day. In the work here reported, three cows were used in each group, and approximately 7,000, 170,000, and 340,000 Sherman-Munsell rat units were fed per day. The results of the calculations for each individual period and the totals of the five periods are given in Table 10. While there are some TABLE 10. Utilization of vitamin A potency for butterfat Sherman-Munsell units per cow per day Period Period Period Period Period Total for 1 2 3 4 5 5 periods In butter, series 3.... 19 .519 14 .425 11.640 9 .230 6 ,019 60 .833 In butter. series 0.... 16 .821 12 .087 5 .116 3 .715 1 .895 39 .634 In butter. gain over 0 2 .698 2 .338 6 .524 5,515 4 .124 21 .199 In feed. series 3 . . . . . . 194 .166 197 .810 195 .851 171 .553 167 .620 927 .000 In feed, series 0 . . . . . . 7 .900 7 ,751 7 .567 6 .768 5 ,372 35 .358 In feed, gain over 0. . 186 .266 190 ,059 188 .284 164 .785 162 .248 891 .642 Percentutilized..... 1.45 1.23 3.46 3.35 2.54 2.38 In butter, series 6.. . . 26 .758 20 .992 15 .113 11.474 7 .420 81 .757 ~ In butter. series 3. . . . 19 .519 14 .425 11 .640 9 .230 6 .019 6O .833 In butter. gain over 3 ‘ 7 .239 6 .567 3 .473 2 .244 1 .401 20,924 In feed, series 6 . . . . . . 356 ,O58 373 .671 357 .324 315 .619 306 .946 1 .709 .618 In feed, series 3 . . . . . . 194 .166 197.810 19S .851 171,553 167 .620 927 .000 In feed, gain over 3 . . 161 .892 175 .861 161 .473 144 .066 139 .326 782 .618 Per cent utilized. . . 4.47 3 .73 2.15 1.56 1 .01 2 .67 In butter. series 6.... 26 .758 20 .992 15 .113 11.474 7 .420 81 .757 In butter, series 0.. . . 16 .821 12 .087 5 .116 3 .715 1,895 39 .634 In butter, gain over 0 9 .937 8 .905 9 ,997 7 .759 5 .525 42 .123 In feed. series 6 . . . . . . 356 .058 373 .671 357 .324 315 .619 306 .946 1,709 .618 In feed. series 0 . . . . .. 7 .900 7 ,751 7 .567 6 .768 5 ,372 35 .358 In feed, gain over 0. . 348 .158 365 .920 349 .757 308 .851 301 .574 1 .674 .260 Per cent utilized... 2.85 2.43 2.86 2.51 1.83 2.52 differences between these various periods, the results on the whole are quite uniform. On an average, 2.5% ofthe vitamin A potency of the feed was found in the butter after allowance was made for vitamin A 16 BULLETIN NO. 536, TEXAS AGRICULTURAL EXPERIMENT STATION stored in the body of the cows, on the assumption that the quantity stored in each group of 3 cows was equal. It is evident from these results that the cow is not very eflicient in utilizing carotene of the feed for the production of vitamin A potency in the milk. Only 2.5% of the vitamin A potency was recovered in the butter. In similar experiments with chickens, we found that four units of vitamin A in the feed produced one unit in the egg. The chicken therefore utilizes 25% of the vitamin A fed, which is practically 10 times as much as that utilized by the cow. While these cows utilized only about 2.5% of the vitamin A potency at the high levels fed, it still remains possible that at lower levels the cow utilizes the carotene more efficiently. so that the results previously reported (5) are approximately correct, and that the cow may utilize 10 per cent of the carotene at such levels. This matter requires further study with a larger number of cows than were used in the previous work. Individual Variations in the Vitamin A Potency of Butterfat The vitamin A potency of the butterfat discussed in the preceding pages was estimated in mixtures of the samples (usually 3) from the cows on the same feed for the same period, and not in the individual samples of butterfat, because the number of rats available did not permit testing the large number of samples. Carotene and spectro-vitamin A were estimated in all but one of the individual samples. Sample 40631 was used up before the spectro-vitamin A was run. Carotene was esti- mated by the spectroscopic method previously described (15). Spectro- vitamin A was estimated on the unsaponifiable residue of the butterfat by methods which will be described in full. The spectro-vitamin A was calculated by the same method employed by Baumann and Steenbock (1), and Gillam et al (8,9), and is reported as vitamin A, as was done by them. The calculation is based upon the assumption that the value of E, or density of vitamin A in a 1 per cent solution at 1 cm, is 1600. If 1600 E at 1% and 1 cm equals one million parts per million vitamin A, then one E is equal to 625 parts per million of vitamin A or 3.13 parts per million if E is 100 per cent and 2 cm. We term the results spectro- vitamin A for convenience. Other workers (10) have multiplied E by 1600 to convert the reading to international units per gram, but this factor is not correct for the results we have secured with butterfat, as will appear later. The carotene and the spectro-vitamin A in parts per million for each individual sample of butterfat are given in Table 11. The calculated vitamin A potencies in Sherman-Munsell rat units are also given. These were calculated by the following procedure: The carotene and spectro- vitamin A were averaged for each group of samples on which the vita- min potency had been determined. The average carotene was multi- plied by 1.4 to convert it to Sherman-Munsell rat units. This is the UTILIZATION OF VITAMIN A BY DAIRY COWS 17 factor secured in this laboratory both for carotene dissolved in cotton— seed oil and for the international standard (7). The average carotene TABLE 11. Vitamin A potency of butter in Sherman-Munsell units calculated from analysis VitaAmin Vit. A Units Calcu- Interna- Carotene potency for one lated tional Laboratory Weeks Cow parts spectro Sherman- part _per Vit. A units per Number on ex- N0. per parts Munsell million potency gram ' periment million per units per of spectro in rat (rat units million gram Vit. A units x 1 2 , No alfalfa 40592 O 356 29 .50 . . . . . . . . . . . . . . . 62 74 40631 0 192 7 .98 sample exhausted . . . . . . . . . . . . . . . 40899 0 370 12 59 8.6 . . . . . . . . .. 36 43 40930Average 16.69 9.1 43 2.16 . . . . . . . . .. 40595 1 356 11.29 2 .8 . . . . . . . . . . 33 40 40638 1 192 5.52 3.9 . . . . . . . . . . 32 39 40923 1 370 6.81 3.7 . . . . . . . . .. 33 39 40961 Average . . . . 7.87 3.5 33 6.28 . . . . . . . . . . 40870 356 3.25 3.0 . . . . . . . . .. 17 21 40922 5 192 1.65 2.9 . . . . . . . . . . 15 18 41065 5 370 1.22 1.8 . . . . . . . . . . 9 11 41131 Average . . . . 2.04 2.6 14 4 28 . . . . . . . . . . 41063 9 192 .52 1.8 . . . . . . . . . . 7 8 40927 9 356 1.74 3.2 . . . . . . . . .. 13 16 41256Average 1.13 2.5 10 3.37 . . . . . . . . .. 41102 13 356 1.48 1.6 . . . . . . . . .. 8 9 41215 13 192 .33 1.8 . . . . . . . . . . 7 8 41264 13 370 .47 1 .7 . . . . . . 7 8 41299Average .76 1.7 7 3.49 . . . . . . . . .. 41263 17 192 .46 1 . 8 . . . . . . . . . . 5 6 41354 17 370 .26 1.2 . . . . . . . . . . 3 4 41384Average .36 1.5 4 2.33 . . . . . . . . .. 3 pounds alfalfa — 40579 0 65 13.35 3.7 . . . . . . . . . . 38 45 40582 0 363 8 90 6.8 . . . . . . . . . . 47 57 40639 O 376 6 87 10.7 . . . . . . . . . . 65 77 40921 Average 9.71 7.1 50 5.13 . . . . . . . . .. 40581 1 363 9.37 3.5 . . . . . . . . .. 39 47 40593 1 65 13.37 2.5 . . . . . . . . . . 37 45 40656 1 376 8.65 5.3 . . . . . . . . . . 52 62 40951 Average 10.46 3.8 33 7.46 . . . . . . . . .. 40630 5 363 4.69 3.2 . . . . . . . . . . 19 23 40637 5 65 8.82 2.5 . . . . . . . . . . 22 27 40928 5 376 3 13 3.5 . . . . . . . . .. 18 22 41134Average 5.55 3.1 20 3 95 . . . . . . . . .. 40898 9 363 3 45 3.4 . . . . . . . . .. 25 31 40921 9 65 6.72 3.0 . . . . . . . . . . 28 33 41103 9 376 2.00 3.2 . . . . . . . . . . 22 27 41231 Average 4.06 3.2 25 6.07 . . . . . . . . .. 41060 ' 13 363 1.73 2.9 . . . . . . . . . . 13 15 41064 13 65 7.87 1.4 . . . . . . . . . . 16 19 41220 13 376 .77 3.5 . . . . . . . . .. 13 16 41265Average 3.46 2.6 14 3.52 . . . . . . . . .. 41214 17 65 5.60 2.0 . . . . . . . . .. 13 15 41308 17 376 2.23 3.3 . . . . . . . . .. 11 13 41312Average 3.92 2.7 12 2.41 . . . . . . . . .. 6 pounds alfalfa 40574 364 10.58 6.3 . . . . . . . . . . 58 70 40655 0 301 8.88 6.9 . . . . . . . . . . 60 72 7.8 . . . . . . . . . . 68 81 ' 40867 0 74 10.00 18 BULLETIN NO. 536, TEXAS AGRICULTURAL EXPERIMENT STATION TABLE 11. Vitamin A potency of butter in Sherman-Munsell units calculated , from analysis-—C0ntinued Vitamin Vit. A Units Calcu- Interna- Carotene A potency for one lated tional Laboratory Weeks Cow parts spectro Sherman- part per Vit. A units per Number on ex- N0. per parts Munsell million potency gram ~ periment million per units per of spectro in rat (rat units million gram Vit. units _ x 1.2) 40952 Average . . . . 9.82 7 .0 62 6.89 . . . . . . . . . . 40580 1 364 6.26 3. 1 . . . . . . . . . . 31 37 40868 1 74 13.11 4.8 . . . . . . . . .. 52 63 40869 1 301 9.13 4.8 . . . . . . . . .. 47 56 40955 Average . . . . 9.50 4.2 43 7.07 . . . . . . . . . . 40610 364 - 5.00 3.1 . . . . . . . . . . 28 33 40962 5 74 4.78 2.9 . . . . . . . . .. 26 31 40963 301 5.44 3.2 . . . . . . . . . . 29 35 41132 Average 5.07 3.1 28 6.74 . . . . . . . . .. 40871 364 4.36 2.3 . . . . . . . . . . 18 21 41136 9 74 3.91 3.3 . . . . . . . . .. 22 26 41137 301 5.32 4.2 . . . . . . . . .. 29 34 41218 Average 4.53 3.3 23 5.05 . . . . . . . . .. 40964 13 364 6. 32 2 .0 . . . . . . . . . . 18 21 41221 13 301 4.49 3.5 . . . . . . . . .. 22 27 41257 13 74 4.01 3.2 . . . . . . . . .. 20 24 41282 Average 4.94 2.9 20 4.51 . . . . . . . . .. 41138 17 364 1.74 2.2 . . . . . . . . .. 6 7 41307 17 301 5.94 3.6 . . . . . . . . .. 14 17 41343 17 74 3.06 3.4 . . . . . . . . .. 10 12 41385 3.58 3.1 10 1.61 . . . . . . . . .. was subtracted from the average vitamin A potency as directly determined on the mixture. The difference is the vitamin A potency due t0 the spectro-vitamin A. This difference was therefore divided by the average spectro-vitamin A in the sample to get a factor to convert spectro-vitamin A to rat units. A different factor was thus secured for each mixture. The spectro-vitamin A in the corresponding individual samples was multiplied by the corresponding factor, and the result was considered to be the vitamin A potency due to the spectro- vitamin A. The carotene in each sample was multiplied by 1.4, and the vitamin A potency so secured was added to that calculated from the spectro-vitamin A, and the total was the calculated Sherman-Munsell units of vitamin A potency. These are given in Table 11 for each sample. (in rat units) The carotene content of the individual butterfat secured 5 days after calving varied from 6.87 to 29.50 parts per million. Excluding the butter containing 29.5 parts per million, which Was extremely high in carotene, the variation was from 6.87 to 13.35 parts per million. Cow 356, which gave the butterfat containing 29.50 parts per million of carotene in the first period, continued to give butterfat containing con- siderably more carotene than the other two cows during the other periods. N0 butterfat was secured from this cow during the last period. The vitamin A potency of the butterfat of this cow was also the highest of the threes in the same group for all the periods in which it was collected. <.;;¢..\;..-..i.s_. ‘~ “'7 UTILIZATION OF VITAMIN A BY DAIRY COWS f 19 The vitamin A potency of the butterfat of cow 370 was less than that of the other two cows in the periods for \which it was collected. In three of the periods the differences were large; in the others they were small. The carotene in the butter from cow 370 was also usually lower than that of the others in the group. Both the carotene content and the vitamin A potency of the butterfat of cow 356 was higher during all periods than those of the other two cows in the same group. The vitamin A potency of the butterfat of cow 65 was higher than that of the other two cows in the same group for the last four samples, but slightly lower in the first two samples. The carotene content of the butterfat of this cow No. 65 was apparently higher than that of the other two in all samples. The vitamin A potency of the butterfat of cow 301 was higher than that of the other two cows in the same group in all except the first two periods, though the carotene was in some cases higher and in other cases lower than that of the other two. , It appears, therefore, that some cows may have a greater power than 4“ others to secrete vitamin A and carotene into the butter. Rate of Utilization of Vitamin A Potency (Carotene) Work reported in Texas Bulletin 495 (5) shows that although the ; vitamin A content of butter decreased during the lactation period of the ‘cow, this decrease was not due to the inability of the cow to utilize vitamin A, because when cows previously producing butter containing only one or five units of vitamin A were placed on pasture, the vitamin A ipotency of the butter increased to 25 or 35 units per gram within two weeks. In order to estimate how rapidly the cow transferred the carotene i from the feed to the butterfat, several lots of cows were first depleted of ; vitamin A by being fed feed low in this vitamin for several months. They (were then placed upon the feed to be tested and samples of butter were taken at regular intervals. In the first experiment of this kind, after a depletion period of 60 days, ; the cows were placed upon pasture for five hours a day. The results are A given in Table 13. It is seen that the vitamin A potency of the butter Liincreased from 12 units per gram to 40 or 50 units per gram within ‘three days. A maximum was thus attained in three days after the cows Iwere put» on pasture. After this time, there was some decrease. As shown jin Texas Bulletin 513 (15), the carotene content of this butter con- F