Effect of dietary vitamin E on the performance of broilers and quality of broiler meat during refrigerated and frozen storage.

Abstract

Experiment 1 was carried out with 220 one-day-old broiler chicks to evaluate the effect of 11 different levels of vitamin E supplementation (viz. 0 to 200 mg a-tocopheryl acetate/kg diet) on the production performance of broilers and oxidative stability of frozen broiler carcasses. The diets with vitamin E levels of 0 to 100 mg were fed from day-old to 42 days of age, and the diets with vitamin E levels of 120 to 200 mg were fed from 21 to 42 days of age. The oxidative stability, evaluated by thiobarbituric acid reactive substances (TBARS), was determined after 30, 90, 120 and 150 days of storage at -20 ?C. There were no differences in weight gain (2.29 ? 0.397 kg) or feed conversion ratios (1.85 ? 0.111 kg feed/kg gain) between dietary treatments. TBARS values increased with increasing time of storage (basal diet: day 30 = 1.71 ? 0.51; day 150 = 4.89 ? 0.51), but decreased with increasing vitamin E levels (day 150: basal = 4.89 ? 0.51; 100 mg/kg = 1.09 ? 0.27). Experiment 2 was carried out with day-old broiler chicks to evaluate the effect of five levels of vitamin E supplementation (viz. 0 to 160 mg a-tocopheryl acetate/kg diet) on performance parameters and the oxidative stability of refrigerated carcasses. The experimental diets were fed from day-old to 42 days of age. Oxidative stability, evaluated by TBARS, colour deterioration and microbiological stability was determined after 0, 4, 8, 10 and 12 days of storage at 4 ?C. Fatty acid analysis was done on samples obtained on days 0 and 12. There were no differences in total weight gain (2.37 ? 0.467 kg) or feed conversion ratio (1.88 ? 0.117 kg feed/kg gain) between dietary treatments. TBARS values increased with increasing storage time, but decreased with increasing vitamin E levels. There were no differences between treatments for colour measurements for L* (44.97 ? 0.662), a* (5.23 ? 0.315) or b* (12.76 ? 0.321) values. Microbiological counts increased over time, but dietary vitamin E concentration had no effect. There were no differences between dietary treatments for any of the groups of fatty acids measured (SFA: Day 0 = 26.1 ? 1.13 %, Day 12 = 26.1 ? 1.17 %; MUFA: Day 0 = 41.4 ? 1.46 %, Day 12 = 40.2 ? 2.28 %; PUFA: Day 0 = 32.4 ? 1.95 %, Day 12 = 33.8 ? 2.52 %). Similarly, fatty acid proportions did not change over time. There were no differences between dietary groups for mean muscle pH (6.01 ? 0.206). South African Journal of Animal Science, Vol 31, Issue 3, Oct – Dec (2001): pp.158-173 Key Words Broiler meat, Vitamin E, TBA, Fatty acids, Shelf life, Refrigeration, Frozen storage, Poultry