Abstract

ABSTRACT The objectives of this experiment were to determine the effects of high dietary levels of vitamin E on growth performance and pulmonary hypertension syndrome (PHS) mortality. Male broiler chicks (Cobb 500) were randomly assigned to one of four dietary treatments consisting of standard starter and grower diets supplemented with 0, 17, 46, and 87 mg dl-a-tocopherol acetate/kg. To encourage the development of PHS, air temperature in the house was 32 and 28 C for Weeks 1 and 2, dropped to 18 C during Week 3, and kept between 10 and 15 C during Weeks 4 through 7. Also, chicks were placed in floor pens on litter used for five previous flocks and ventilation reduced to increase dust and ammonia in the house. Ammonia levels increased from an initial 18 to 36 ppm on Day 42 with the increase in ammonia corresponding to an obvious increase in dust in the air. Lung and liver tissue obtained at 2, 5, and 7 wk of age were analyzed for tissue a- and g-tocopherol by liquid chromatography. Dietary vitamin E had no effect on body weight, feed intake, or feed efficiency. Cumulative PHS mortality through 7 wk of age was 21 % and was also unaffected by dietary treatment. Liver and lung a-tocopherol concentrations exhibited a dose-response increase to dietary tocopherol and there was a high correlation between lung and liver tissue a-tocopherol (r = 0.72, P < 0.05). Whereas g-tocopherol concentrations in lung and liver were unaffected by dietary treatment, liver and lung exhibited age-dependent increases in both a- and g-tocopherol. Despite dose-dependent increases in tissue a-tocopherol, supplementation of diets with up to 87 mg dl-a-tocopherol acetate had no effect on growth perfor-mance or PHS mortality in broilers under the conditions used in this study.