[A genetic disorder of vitamin A metabolism is recessively white canaries]

A discussion of vitamin A and carotene metabolism in recessively white canaries has been going on for years. This colour canary is reputed to be a 'weak' bird. In the present study, the concentrations of vitamin A, total carotenoid and beta carotene in the serum, liver and feed of both coloured and recessively white canaries were determined. The most important conclusions are: - The normal concentration of vitamin A in the livers of health canaries varies from 500 to 1,500 I.U. of vitamin A per gram of liver. - This is achieved by administering an amount of approximately 15,000 U.U. of vitamin per kg of egg feed. The intake through the feed by each canary will then be approximately 800 I.U. of vitamin A/kg. of body weight daily. - Carotenoids are practically not resorbed from the intestine by recessively white canaries. Vitamin A is also absorbed to a less extent by these birds than it is by canaries which are not recessively white. For their supplies of vitamin A, recessively white canaries are completely dependent on the pressure of vitamin A in the feed. - It would appear to be essential to increase the vitamin A content of the egg feed for recessively white canaries to 20,000 I.U./kg. of egg feed.