Effect of vitamin E and A supplementation on egg yolk alpha-tocopherol concentration

The objective of this study was to asses the effect of dietary dl-alpha-tocopheryl acetate (alpha-TAC) and vitamin A supplementation on egg yolk alpha-tocopherol (alpha-T) concentration. A total of 96 ISA brown hens (a brown-egg laying hen), 32 wk of age, was used. Eight concentrations of alpha-TAC (0, 20, 40, 80, 160, 320, 640, and 1,280 IU/kg diet) were included in a corn-soybean meal-based diet containing 4,000 IU of vitamin A/kg diet. Production parameters were not affected by dietary treatment. Interhen variation in yolk alpha-T concentration increased at higher dietary intakes. Logarithmic transformation stabilized variance and showed the existence of a linear relationship between dietary alpha-TAC supplementation level and alpha-T egg yolk concentration (P < 0.001). As the dietary concentration of alpha-TAC rose, efficiency of uptake of alpha-T from feed to yolk decreased linearly (P < 0.001). A parallel experiment was carried out in which four additional groups of hens were fed diets containing four levels of dietary alpha-TAC (0, 40, 160, and 640 IU/kg) and 40,000 IU vitamin A/kg diet. A significantly lower egg yolk alpha-T concentration was found in hens fed diets including the highest level of vitamin A supplementation (P < 0.001). No interaction of dietary alpha-TAC and vitamin A concentrations was observed on egg yolk alpha-T concentration. No effect of dietary treatment was observed on yolk oxidation and other egg quality characteristics.