Influence of Dietary Vitamin A on Carotenoid Utilization, Nitrogen Retention and Energy Utilization by the Chick

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Abstract
The effect of feeding high dietary levels of vitamin A palmitate on the utilization of carotenoids, nitrogen retention and energy utilization by the chick was studied. Five-week-old chicks were fed diets supplemented with 4,400, 26,400, 158,400, and 475,200 IU of vitamin A/kg of diet for a 3-week experimental period. Yellow corn was the dietary source of carotenoids. A consistent decrease in the carotenoid content of serum, liver and skin was obtained with the increase in vitamin A level of the diet. Significant (P < 0.01) negative correlation coefficients were calculated when values of serum, liver, and skin carotenoids were plotted against logarithm of dietary vitamin A level. A consistent decrease in the absorption of carotenoids was found when the output of carotenoids in the excreta was measured. Absorption of carotenoids was determined by the conventional total collection method and by the chromic oxide indicator technique. The results obtained by the 2 methods were essentially similar. Both N retention and metabolizable energy of the diets were depressed with excess vitamin A supplementation. An adverse effect of excess body storage of vitamin A on the utilization of carotenoids was also noted.