Supplementing hen diets with vitamins A and E affects egg yolk retinol and α-tocopherol levels

Laying hens were fed a basal diet supplemented with increasing levels of retinyl acetate and alpha-tocopheryl acetate to investigate the effects of vitamin A and E supplementation upon egg yolk retinol and tocopherol concentrations. The high concentration of added vitamin E caused a decline in egg production and poor feed conversion. Egg quality was not affected by vitamin A and E levels. Yolk retinol concentration was enhanced by added vitamin A, from 24.6 IU/g for eggs from the control group, to 33.6 and 37.7 IU/g of yolk when hens were fed 15,000 and 30,000 IU/kg of diet. Yolk alpha-tocopherol was significantly increased by dietary tocopherol supplementation, ranging from 10.9 mug/g (control group) to 160.6, 264.1, and 383.2 mug/g of yolk, respectively;, when 200, 400 and 600 mg/kg of ration were added, respectively. Yolk alpha-tocopherol was increased by 24.9 and 44.0% with increasing vitamin A supplementation at 15,000 and 30,000 IU/kg of diet, respectively. When correlation coefficients and regression equations were calculated, it was found that yolk alpha-tocopherol decreased (P < 0.05) as supplemental vitamin A increased, indicating the adverse effect of dietary vitamin A on yolk tocopherol deposition. The nutritional value of eggs, related to retinol and tocopherol, can be improved by dietary manipulation of hens diet, but attention must be focused on their inter-relationship.