The effect of thyroxine and thiouracil on the composition of milk. 2. The carotene and vitamin A content

Publisher Website
Google Scholar
Abstract
The metabolism of carotene in 6 lactating cows and in 8 lactating goats was investigated. Goat''s milk contained 142 I.U. vit. A/100 ml., all of it in the ester form. Cow''s milk contained 88 I.U. vit. A, 6% of which was in the alcohol form. Unlike the cow''s milk, that of goat did not contain carotenoids, but in the colostrum and in the liver of goats beta-carotene was demonstrated. When the cows were deprived of carotene for 2 weeks, their milk yields were not affected, but the concns. of vit. A and carotene decreased. At the same time the proportion of vit. A present in the alcohol form increased. Superimposing thyroxin treatment upon carotene deprivation caused even greater increases of vit. A alcohol in the milk. On re-instatement of the carotene-containing diet the concns. of both carotene and vit. A increased at rates which were enhanced by thyroxin and diminished by thiouracil. The effects on vit. A and carotene of discontinuing thyroxin while the cows were still ingesting carotene were similar to those produced by injecting thiouracil. Conversely, the effects of discontinuing thiouracil were similar to those of giving thyroxin. Thyroxin and thiouracil produced changes in the composition of goat''s milk which were similar to those found in cow''s milk.