Minimum Vitamin A and Carotene Requirements of Mammalian Species

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Abstract
Data are presented on time required to deplete vitamin-A reserves of horses and on their minimum requirement for vitamin A and for carotene. The more conspicuous symptoms of vitamin-A deficiency in the horse are described. The data previously published on vitamin-A requirement of cattle, sheep, and swine were re-evaluated and a summary table presents all of the data from this laboratory on vitamin-A and carotene requirements of various species expressed both by weight and in international units. The agreement of these and other data, with regard to the minimum to prevent earliest symptoms and also the higher levels necessary for storage and reproduction in animals and optimal dark adaptation in man are discussed. The necessity for two standards for expressing requirements, one for vitamin A and one for carotene is pointed out. These are illustrated by means of a table and a graph.