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 al pha -tocopheryl acetate (DTA) concentrations in light-weight lambs on muscl e alpha -tocopherol accumulation and on quality characteristics of stored m eats. Thirty-two Manchego lambs were randomly distributed to four groups an d given diets containing four levels of DTA (20, 270, 520 and 1020 mg/kg di et) 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 die tary supplementation level was observed on muscular alpha -tocopherol conce ntration, 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 mu scle vitamin E concentration on thiobarbituric acid reactive substance on d ay 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 tar get muscle alpha -tocopherol concentration of 5(.)4 mg/kg. Evolution of sur face redness of lamb chops also showed a linear and quadratic effect of die tary 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 -t ocopherol concentration in the range 5(.)3 to 5(.)6 mg/kg muscle for optimu m red colour stability. Surface luminosity showed no effect of dietary trea tment at days 0, 3 and 6 of storage but a linear (P < 0(.)01) plus quadrati c (P < 0(.)05) effect on day 9 of storage. Broken line analysis at this poi nt indicated a target muscle alpha -tocopherol concentration of 3(.)2 mg/kg . It is concluded that the effectiveness of dietary alpha -tocopheryl aceta te supplementation depends on the meat quality attribute assessed. A signif icant 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 particul arly 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.