The Vitamin a Requirement of Growing Turkeys

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Abstract
Three experiments were conducted in which 228 male Broad Breasted Bronze turkeys were used to determine the vitamin A requirement of growing turkeys, the experiments being so designed as to allow the application of three criteria: growth, histopathology, and vitamin A concentration in the blood and liver. A basal vitamin A deficient diet was used which, when adequately supplemented with vitamin A, was capable of producing birds averaging 2,000 gm in weight at 8 weeks of age. This diet was supplemented with levels of 0, 150, 300, 600, 1,200, 2,400, 4,800 and 7,200 I.U. of vitamin A per 100 gm of feed. From the analysis of growth curves, the point of greatest response was calculated to be 1,683 I.U. of vitamin A per 100 gm of feed. Histological examination of the brain revealed no conclusive results. The plasma level of vitamin A in lots receiving less than 1,200 I.U. of the vitamin per 100 gm of feed was greatly influenced by the dosage of vitamin A in the diet. Lots receiving more than 1,200 I.U. of vitamin A per 100 gm of feed showed little effect of the dosage on plasma levels. Lots receiving less than 1,200 I.U. of vitamin A per 100 gm of feed were unable to maintain their liver stores of the vitamin with increased age, while lots receiving more than 1,200 I.U. per 100 gm of feed increased their liver stores as age advanced. It is concluded on the basis of the growth data and the plasma levels and liver storage of vitamin A that the vitamin A requirement of growing turkeys is 1,700 I.U. of the vitamin per 100 gm of feed.