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Supplementing Hen Diets with Vitamins A and E Affects Egg Yolk Retinol and -Tocopherol Levels

Departamento de Clínica Médica, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, Cidade Universitária Armando de Salles Oliveira, Av. Orlando Marques de Paiva 87, São Paulo, 05508-000, Brazil

Correspondence: A. V. Mori, E-mail: cxmendon{at}usp.br

Laying hens were fed a basal diet supplemented with increasing levels of retinyl acetate and a-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 -tocopherol was significantly increased by dietary tocopherol supplementation, ranging from 10.9 µg/g (control group) to 160.6, 264.1, and 383.2 µg/g of yolk, respectively, when 200, 400 and 600 mg/kg of ration were added, respectively. Yolk -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 -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.

Key Words: egg yolk • hen • retinol • vitamin A • vitamin E • -tocopherol • laying performance