Effects of supplementation with vitamin E on the performance and the tissue peroxidation of broiler chicks and the stability of thigh meat against oxidative deterioration

Two experiments were conducted: Expt 1 determined the optimal allowance of vitamin E in the diet for broiler chicks aged 0-3 weeks; Expt 2 investigated the effects of different dietary levels of vitamin E (a-tocopherol) on the performance and the oxidative stability of thigh meat of broiler chicks during storage. In Expt 1, 1-day-old 900 broiler chicks were allocated to five treatments, each with six replicates (cages) of 22 as-hatched chicks for performance evaluation, and another cage of 45 male chicks for determining plasma and hepatic alpha -tocopherol and thiobarbituric acid reactive substances (TBARS) concentration in blood and liver. The basal dietary alpha -tocopherol concentration was 13 mg/kg, and the five alpha -tocopherol acetate supplementation levels were 0, 5, 10, 50 and 100 mg/kg. For 0-3-week-old broiler chicks fed with maize-soya bean meal-soya oil type diet, supplementation of vitamin E did not influence the feed intake, but tended to improve growth and feed utilization, however there was no significant correlation between performance and vitamin E supplementation level. Significant positive correlations existed between dietary supplemental vitamin E level and plasma or hepatic alpha -tocopherol concentrations (P < 0.05), and a negative correlation with hepatic TEARS levels no matter at what age (11, 16 and 21 days). In Expt 2, 2200 broiler chicks were randomly allocated to five treatments with four replicates (pens) in each. Chicks were fed ad Libitum five pellet diets supplemented with vitamin E at 5, 10, 20, 50 and 100 mg/kg of diet. respectively. The basal dietary -tocopherol level of grower and finisher diets were 7 and 6 mg/ kg) respectively. Supplementation of vitamin E tended to improve growth and feed utilization of birds during 0-3 weeks of age, but the performance from 0 to 6 weeks of age were not influenced. The hepatic alpha -tocopherol concentrations of 6-week-old chicks linearly increased with the dietary vitamin E levels (R-2 = 0.98, P < 0.001). The content of TEARS in the thigh meat over 4 days of storage under 4C was significantly decreased by increasing dietary vitamin E level (P < 0.05). There was a significant inverse relationship between TEARS value in the thigh meat and the dietary vitamin E level (R-2 = 0.93, P < 0.01). Supplementation of vitamin E significantly improved the meat quality stability substantially against oxidative deterioration. Comparing the hepatic alpha- tocopherol levels of chicks in Expts 1 and 2, total allowance of dietary alpha -tocopherol of 20-30 mg/ kg could sustain relatively constant hepatic alpha -tocopherol level at round about 2-2.5 mug/kg. (C) 2001 Elsevier Science B.V. All rights reserved.