Vitamin A studies with rats and pigs

Abstract
The vit. A activities of carefully purified prepns. of xeaxanthin, vit. A alc, vit. A ester and [beta]-carotene were assayed on pigs and rats. Zeaxanthin was inactive for both species. Pigs made less efficient use of [beta]-carotene than rats and for their minimal requirements required about 300 I.U. of [beta]-carotene or 100 I.U. of preformed vit. A daily per 10 lb. live wt. No difference was found in the biological activities of vit. A alc. and vit. A natural ester in either pigs or rats.