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densed milk is so generally used in the Tropics. Sweet condensed milk will keep indefinitely as long as it is protected from insects. The evaporated milk will decompose, if not kept on ice, soon after the can is opened. If large cans are opened there is considerable waste in the use of evaporated milk unless it is all used at once. We overcome this by purchasing the smallest possible cans of evaporated milk so that one is used every day in the preparation of the milk for the feeding of babies. On the other hand, with the sweet condensed milk, as long as it is protected it will keep more or less indefinitely.

I referred to the use of orange juice. If orange juice is not available you can use any other kind of fresh fruit juice, or tomato juice. Owing to the acid character of tomato juice vitamin C is not entirely destroyed during the process of canning, so that when other sources are not available canned tomato juice is acceptable.

Chairman Rose. If there is no further discussion, we will proceed to the next paper, “ Variations of the vitamin A content of cow's milk under different conditions of feeding,” by Capt. John Golding, head of the chemical department, National Institute for Research in Dairying, England. [Applause.]

VARIATIONS OF THE VITAMIN A CONTENT OF COW'S MILK UNDER

DIFFERENT CONDITIONS OF FEEDING.

Capt. John GOLDING, D.S.O., F.I.C., head of the chemical department, National

Institute for Research in Dairying, Reading, England.

The guaranty of fresh milk as the most suitable food for the young mammal of the same species rests on the provisions of nature. The acceptance of fresh cow's milk as food of special value for human beings has been recognized from time immemorial.

This value is not entirely dependent on the nutrients which milk contains, nor can it be summed up in calories, for there are also present certain physiological principles, among which, as the researches of the last few years have shown, the vitamins play a sig. nificant part.

The nature of milk as a complete food insures the presence of all the factors necessary for the growth and well-being of the young animal. Four vitamins have already been defined. Under abnormal conditions of feeding, a variation of these vitamins in the milk of the lactating female might be expected, and this was first recognized by McCollum, Simmonds, and Pitz (1916) in their experiments on rats fed on diets deficient in the vitamins A and B. A considerable amount of confirmation of this variation has been produced from other sources. Drummond, Coward, and Watson (1921) have demonstrated that the chief cause of such variation lies in the diet of the animal.

While the experiments reported in this paper were in progress, the results of the work of Kennedy and Dutcher (1922) were published, from which the conclusion was reached that "the presence of the vitamins A and B in cow's milk is entirely dependent on their occurrence in the ration.” Further, they stated that stall-fed cows will produce a milk rich in vitamins provided that a suitable combination of grains and leafy food is given to the cows. Kennedy and

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Dutcher also consider the quantity of milk which is adequate lo furnish vitamin A or B to a rat to be as high as 10 cubic centimeters a day, and they definitely state that 5 cubic centimeters do not furnish enough of either vitamin to meet the requirements of growing rats. This statement, together with that of Osborne and Mendel, when compared with the results of Hopkins, who obtained growth in rats with 2 cubic centimeters of milk given to each animal daily, might indicate that the milk at Cambridge has sometimes a greater natural richness in vitamin A than the milk which was used in the experiments in America.

Another point which has to be considered in experiments on vitamin A is the ability of the animal to store any excess of this factor in its body tissues. In experiments conducted on pigs (Drummond, Golding, Zilva, and Coward, 1920), a storage of vitamin A in the animal body was demonstrated when this factor was supplied in excess in the diet; and in further experiments (Golding Zilva, Drummond, and Coward, 1922), a sow fed on a deficiency diet proved herself capable of raising a litter of healthy pigs to the weaning stage by drawing upon the reserve of vitamins previously stored in her body when on full diet.

In the autumn of 1921 it was decided to start a series of experiments at the National Institute for Research in Dairying, with a view to ascertaining the effect of winter feeding on the vitamin A content of milk fat and also the effect of administering small supplements of a rich source of that factor, such as cod-liver oil, during the period when the animals are usually receiving indoor rations tending to be deficient in the vitamin.

In this work I was fortunate in having the cooperation of Prof. J. C. Drummond and Miss K. H. Coward, of University College, London; Dr. S. S. Zilva, of the Lister Institute, as well as that of my colleague, Mr. J. Mackintosh.

A joint paper on the results of this work has been published in the Journal of Agricultural Science, 1923.

The experiments were planned with the intention of studying the variations of the vitamin A content in the milk of cows kept under winter conditions, such as prevail in the north of England, viz., stall feeding only, of cows partly stall fed and partly at pastur viz., south country conditons, and of the same cows fed on pasture in the autumn and spring. The vitamin A, or the growth promoting factor, was estimated in the butter made from the milk of the experimental cows by observing the influence of daily supplements of known weight on the growth of rats, whose growth had been brought to a standstill by a deficiency of that vitamin.

The amount of butter, in grams, necessary is here termed the growth dose," which is, of course, inversely proportional to the concentration of vitamin in the butter.

It was intended that the group of stall-fed cows should be given a typical winter ration deficient in vitamin A until an examination of the milk fat showed that the concentration of the accessory factor had dropped considerably. The group was then to be subdivided into two lots, one of which was to receive a daily dose of a highly potent cod-liver oil, and the other, as a control, an equivalent dose of inactivated olive oil.

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The daily rations of each stall-fed cow consisted of 50 pounds mangolds, 17 pounds seeds hay, and a quantity of concentrates varying from 8 to 15 pounds per day and consisting of maize gluten feed, 4 parts, maize meal, 5 parts, and decorticated ground nut cake, 3 parts. The cows began to feed on this ration on December 3, 1921, and continued till January 21, 1922, when 24 parts of maize meal were replaced by 23 parts crushed wheat, this diet being continued till April 1. The seeds hay was of excellent quality and was made in the good season of 1921. It was composed of Italian rye grass, cocksfoot, and other grasses, with some clover and legumes. The diet of the stall-fed cows, receiving no green food, so affected the vitamin A content of their milk that a daily dose of 1 gram was required per rat to produce growth, thus showing a tenfold reduction in potency since the commencement of the experiment, at which time 0.1 gram only was required.

The reduction of the vitamin A content was accompanied by a marked disappearance of the natural pigment of the butter: Units of pigments December 3, 1921, 1.4; units of pigments January 31, 1922, 0.5.

From March 4 to May 31, cod-liver oil was given to two of the cows in daily doses increasing from 15 grams to 120 grams per cow. The growth dose was determined with each increment, and it finally equaled in its vitamin content the highest value of grass-fed butter. No flavor was observed in the butter consequent on the addition of this quantity of cod-liver oil.

The pigment value, however, continued to decrease from 0.6 to 0.35 during this period of cod liver oil feeding. The weight of milk and the percentage of fat were determined at each milking, but revealed that no obvious effect was produced by the administration of this quantity of cod-liver oil.

The partially grass-fed cows received a basal diet similar to that of the entirely stall-fed animals. During January and February

. the vitamin A content of their milk fat fell almost as low as that of the stall-fed cows. This observation agrees with that reported by Kennedy and Dutcher, that access to open pasture will not assure a ration rich in vitamins unless the pasture is always fresh and green. Neither dry, parched pastures nor dormant winter pastures can compare with the value of fresh green grass in this respect. As the spring advanced and fresh grass began to grow, the vitamin A content of the butterfat improved and its color attained a higher pigment value than in the autumn.

Since this paper was written, another group of experiments on the same subject has been completed. In this series the milk of individual cows has been examined in preference to the mixed milk of small groups of cows, as was done in the case of the first series referred to above.

The experiments were started on December 5, 1922, and continued till July 10, 1923, during which time three cows were available.

At the start the diet consisted of meadow hay, 17 pounds per cow per day, Yellow Globe mangel 50 pounds, and concentrates 9 pounds. The concentrates were made up of a mixture of maize gluten feed, 1 part, soy bean meal, 1 part, and crushed wheat, 1 part.

The extracted soy bean meal and other constituents of the diet were selected to admit of the addition of oils, the effect of which addenda to the ration on the composition of the butter is also being studied.

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1 Inactive.
Fall in vitamin activity after the seeds hay period occurred in butter from all cows.
A question mark in front of a value means probable activity on the amount following the question mark
Growth dosage for last butter from Lucy has not been obtained yet.

As seen from these figures, the vitamin value rose at first on the basal diet alone, without the addition of vitamin-containing constituents, and reached a potency of 0.3 gram per growth dose.

This apparent anomaly led us to examine closely the vitamin values of the component parts of the basal ration, which resulted in the discovery that the 1922 meadow hay used in 1923 was richer in vitamin A than the 1921 seeds hay used in 1922. Some seeds hay harvested in 1922 was obtained and substituted for the meadow hay, with the result that the vitamin content of the butter dropped again to a growth dosage of 1 gram.

This result is of especial interest in view of the work on calcium assimilation published at the University of Wisconsin, by Hart and others, who obtained negative calcium balances with alfalfa hays cured in the windrow with exposure to air and light for four days, but positive calcium balances in earlier experiments with alfalfa hay cured under caps. Our experiments, therefore, give comfirmation to their statement that: “ These differences in effect of the two alfalfa hays may be attributed to a difference in the degree of destruction during the curing process of the vitamin assisting calcuim assimilation."

The addition of cod-liver oil to the food of the cows in our 1923 experiments again produced a tenfold increase in the growth-promoting properties of the butter, and although in these experiments as much as one-half pound per day per cow was finally given, no taste was detected in the milk or butter. It is to be noted that a clear good quality oil was used.

The work on the effect produced on the composition of the butter by these additions of oil is not yet completed.

The natural variations in the quantity and quality of the milk yielded make it impossible to express an opinion on this aspect of the work at present.

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The results show that winter feeding, as practiced in parts of England, may reduce the value of milk as a source of the growthproducing vitamin A, to one-tenth its summer value, but that this can be restored by feeding a substance rich in vitamin A, such as cod-liver oil.

In conclusion, it is as yet difficult to assess fully the clinical and physiological significance of this vitamin variation which is controlled by the nature of the diet; but it will be seen that it is now a definitely established scientific fact, and consequently I think that it is fairly evident that the producer, aiming at the production of the very best milk, will have to take cognizance of these results.

REFERENCES.

DRUMMOND, COWARD, and WATSON. (1921.) Biochem. Journ., 15, No. 4, 540. DRUMMOND, GOLDING, ZILVA, and CoWARD. (1920.) Biochem. Journ., 14, No. 6,

742. DRUMMOND, COWARD, GOLDING, MACKINTOSH, and ZILVA. (1923.) Journ. of

Agric. Sci., 13, 144. GOLDING, Zilva, DRUMMOND, and COWARD. (1922.) Biochem. Journ., 16, No.

3, 394. HOPKINS. (1920.) Biochem. Journ., 14, 721. KENNEDY and DUTCHER. (1922.) Journ. Biol. Chem., 50, 339. McCOLLUM, SIMMONDS, and Pitz. (1916.) Journ. Biol. Chem., 27, 33. HART, STEENBOCK, HOPPERT, and HUMPHREY. (1922.) Journ. Biol. Chem.,

53, 21. Hart, STEENBOCK, HOPPERT, BETHKE, and HUMPHREY. (1923.) Journ. Biol.

Chem., 54, No. 1, p. 75-89.

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Chairman Rose. Would you like to discuss this paper of Captain Golding's?

Dr. ANTONIO PEÑA CHAVARRIA (Colombia, South America). I would like to know if the vitamin content of the milk of the cow raised in the valley is the same as that of cows raised in the mountains.

Captain Golding. I, of course, hate to speak generally. We have experimented with pigs running on the high plains in England where the pasture was very much burned up, and they certainly suffered from vitamin deficiency. I would say the richer, greener grass in the valley might well produce a milk richer in vitamins than the poorer grass of a mountain country.

Dr. A. H. FLICKWIR (Houston, Tex.). I would like to ask Captain Golding what experiments he has made with cottonseed oil, what effect that would have on the vitamin, and if that could not be used in place of the cod-liver oil.

Captain GOLDING. We have not used cottonseed oil. Of course, cottonseed cake is commonly used in feeding cows in England, but all these vegetable oils are very poor in vitamins. We rendered olive oil inactive in the first year of our experiment. Because of the bubbling air in it, the quantity of vitamins contained in the olive oil is very small. In our second year we experimented with arachnes oil and coconut oil. There was no indication of vitamins being supplied in the butter of those cows.

Chairman Rose. Are there any other questions? If not, we will thank Captain Golding for his paper and go on to the next. Dr. Cornelia Kennedy will not be present to read her paper, so we will pass that for the present and substitute for it the subject, “ The use

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