Dose-response effect of dietary vitamin E concentration on meat quality characteristics in light-weight lambs

The research was carried out to evaluate the effect of different dietary alpha -tocopheryl acetate (DTA) concentrations in light-weight lambs on muscle alpha -tocopherol accumulation and on quality characteristics of stored meats. Thirty-two Manchego lambs were randomly distributed to four groups and given diets containing four levels of DTA (20, 270, 520 and 1020 mg/kg diet) for 6 weeks. Lambs were slaughtered at live weights ranging from 23(.)5 to 26(.)4 kg. A linear (P < 0.001) and quadratic (P < 0.001) effect of dietary supplementation level was observed on muscular alpha -tocopherol concentration, which fitted the following equation: mg muscle alpha -tocopherol per kg muscle = 1.78(s.e. 0(.)18) + 7(.)08 (s.e. 0(.)89)(1 - e(0.0012DTA))) (P < 0(.)001, R-2 = 0(.)99). There was a linear effect (P < 0(.)001) of muscle vitamin E concentration on thiobarbituric acid reactive substance on day 0 of storage, but a linear plus quadratic effect (P < 0(.)001) on days 3, 6 and 9. Broken Zinc analysis of data at day 9 of storage indicated a target muscle alpha -tocopherol concentration of 5(.)4 mg/kg. Evolution of surface redness of lamb chops also showed a linear and quadratic effect of dietary treatment on days 3 and 6 of storage, but only a linear effect on day 9. Broken Zinc analysis of data at 3 and 6 days indicated a target alpha -tocopherol concentration in the range 5(.)3 to 5(.)6 mg/kg muscle for optimum red colour stability. Surface luminosity showed no effect of dietary treatment at days 0, 3 and 6 of storage but a linear (P < 0(.)01) plus quadratic (P < 0(.)05) effect on day 9 of storage. Broken line analysis at this point indicated a target muscle alpha -tocopherol concentration of 3(.)2 mg/kg. It is concluded that the effectiveness of dietary alpha -tocopheryl acetate supplementation depends on the meat quality attribute assessed. A significant positive effect for lipid oxidation can be reached even at the lower supplementation level utilized in this experiment (270 mg/kg diet). However, considering the protecting effect at different storage times and particularly the effect on meat surface redness, the optimum level would be in the range 5(.)3 to 5(.)6 mg/kg muscle, which correspond to a dietary inclusion of 550 to 625 mg alpha -tocopheryl acetate/kg diet.