Shark Liver Oil and the Vitamin A Potency of Milk

IN'TRODUCTION"The vitamin A activity of winter milk usually is lower than that of summer milk due to the reduced carotene intake of cows maintained on winter rations.It is well known that the vitamin A activity of milk is dependent on the level of carotene and vitamin A in the ration.The data presented herein are the result of an attempt to increase the vitamin A potency of winter milk.REVIEW OF LITERATURE l~eports in the literature have shown that feeding carotene, whether as green pasture or hay in amounts as high as 6,000,000 International Units (I.U.) of vitamin A per cow per day, has never resulted in butter containing more than 56 I.U. of vitamin A per gram, nor milk containing over 2500 units per quart (2,18,20,21,22).Archibald and Parsons (1) fed a fortified cod-liver oil with the dairy ration and reported a significant increase in the vitamin A level of the milk from these animals as compared with those receiving unsupplemented rations.They reported 3596 units of vitamin A per quart of milk when cod-liver oil (3000 U.S.P. units of vitamin A per gram) was fed at 0.25 per cent level in the grain.The vitamin A assays of the milk in two consecutive years did not agree because of a change in the quality of the roughage used in the basal ration.These investigators noticed a favorable effect on milk production and found no significant effect on the average butterfat content of the milk. Deuel et al.(3, 4) administered 700,000 and 1,400,000 I.U. of vitamin A in the form of shark-liver oil to Guernsey cows £nd observed a corresponding increase in the vitamin A potency of the milk, proportional to the amount of vitamin fed.The basal diet included large amounts of fresh-cut alfalfa and baled alfalfa hay.These workers reported an average of 113 I.U. of vitamin A per gram of butterfat after daily administration of 1,400,000 I.U. of vitamin A as shark-liver oil, and as high as 172 I.U. of vitamin A per gram of butterfat with one animal.These analyses were