Vitamin E and fatty acid content of lamb meat from perennial pasture or annual pasture systems with supplements

The present study investigated the effect of a perennial lucerne and phalaris pasture, or annual pasture with lucerne hay and a range of supplements provided as pellets (700 g/day) on Vitamin E and fatty acid content of skeletal muscle and oxidative stability of lamb meat post-farm gate. Treatments were lambs grazing perennial pasture only (PP); lambs grazing annual pasture with lucerne hay and oat grain pellet supplement (AP); AP with cracked flaxseed (AP+FS); and AP with flaxmeal (AP+FM). After 7 weeks of feeding, lambs were slaughtered after an overnight fast. At 24 h post-slaughter, samples of muscle longissimus lumborum (LL) were collected for determination of fatty acid profile and antioxidant status, as measured by Vitamin E content. Samples were also collected for retail colour assessment of fresh meat at 24 h, 48 h, 72 h and 96 h of post-slaughter. Vitamin E content of the LL from lambs grazing PP was higher (5.9 v. 3.4 mg α-tocopherol/kg, P < 0.01) than that of lambs grazing other treatments. Long-chain n-3 and total n-3 fatty acid contents in the muscle were similar among treatment groups and adequate to claim as a source of n-3. Inclusion of oat grain at 245 g (AP) or at 175 g with flaxseed (AP+FS) or 175 g with flaxmeal (AP+FM) per day in the diet of lambs increased the linoleic acid content (P < 0.05) and the ratio of n-6:n-3 (P < 0.007) in the LL, compared with lambs grazing PP. Oxidative stability of fresh meat evaluated by retail shelf life (retention of redness) and formation of lipid oxidative substance showed no differences among treatment groups and, as indicated by redness (a*-value) over a 96-h display, all values were within the range (>9.5) for quality meat over the time frame used in the present study. The results provided some evidence that inclusion of PP in the diets of lambs during dry seasons (late summer to autumn) is an effective tool of improving the Vitamin E content of muscle tissues at slaughter.