The Vitamin D Requirement of Young Turkeys

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Abstract
An investigation of the vitamin D requirement of young turkeys was made by measurement of the ash content of the tibiae at 4 weeks of age as influenced by various levels of vitamin D in the diet. Under the conditions of the experiment, the highest bone ash was in the neighborhood of 50%. U.S.P. reference cod liver oil produced unsatisfactory growth and calcification when added at a level of 120 units (U.S.P. or A.O.A.C.) per 100 gm. of diet. Higher levels were not fed. A linear relationship between vitamin D level and bone ash was observed in an experiment in which reference cod liver oil was added at levels ranging from 20 to 100 units per 100 gm. of diet. Growth rate of turkeys was markedly influenced by vitamin D; in one experiment the birds receiving an ample supply of the vitamin weighed 93% more than the birds on the basal diet at 4 weeks. Satisfactory growth and calcification in complete absence of sunlight were produced when turkeys received 0.4 gm. of a fish oil blend per 100 gm. of diet. Significantly poorer calcification was produced when 0.3 gm. was used. The oil was tested with chicks and was found to supply approximately 450 units of vitamin D per gram when the turkey basal diet was fed, and 466 units when a modified A.O.A.C. basal diet was used, based on a value of 95 units of vitamin D per gram for U.S.P. reference cod liver oil. The fish oil blend functioned as a source of vitamin D that was more effective, chick unit for chick unit, than reference cod liver oil for turkey poults. The average turkey: chick efficacy ratio of the fish oil blend was about 140 (cod liver oil = 100). Hence the vitamin D requirement of turkeys could not be precisely stated in terms of A.O.A.C. chick units, since the possibility of a differential species response between chicks and turkeys is not considered by such an expression. A value of 200 A.O.A.C. chick units of vitamin D per 100 gm. of diet may be taken as an approximation of the requirement of turkeys for the first 4 weeks to produce maximal calcification in the complete absence of sunlight.