Carotene Balance and Blood-carotene Levels in Heifers and Lactating Dairy Cows, and Their Relation to the Production of Off-flavor Milk

In the course of an investigation of oxidized flavor in milk, it was discovered that four cows were excreting in their feces more carotene ^ than they were consuming. The flavor of the milk from each of these cows was markedly and quickly improved by adding a carotene concentrate ^ to the ration. Since Atkeson and his coworkers (1),^ Fraps and Treichler (Í0), and Moore (18) had already shown that only a small fraction of the total carotene ingested appears in the milk, either as carotene or vitamin A, it was not altogether unexpected that large quantities of carotene should be excreted in the feces. In view of the great losses in the metabolism of carotene, it seemed desirable to examine the nature and quantity of these losses imder variable conditions. The relationship of the excretion of carotene in the feces of cows to carotene intake and to the concentration of carotene in the blood serum was studied. The results are presented in this paper. Except for carotene and vitamin A secreted in the milk, these studies were balance trials. In a previous study, Atkeson and his coworkers (1) showed that when cows were stall-fed green rye only 0.086 percent of a daily intake of 3.5 g carotene was deposited in the butter, as carotene, and only 0.154 percent as vitamin A. From these figures one might conclude that a carotene balance of the type here presented would not be appreciably affected by the small amounts of carotene secreted in the milk either as carotene or as vitamin A. Harris and Ray (14) found that animals without adequate reserves of vitamin C would use a suddenly increased supply much more efficiently than would animals with larger reserves. It was totally unexpected that cows showing evidence of carotene deficiency or even cows with moderate reserves would excrete in their feces carotene from body stores. The analogy to vitamin C, and consideration from this standpoint of certain experiments on children and rats might, however, have suggested this possibihty.