Slaughter and muscle sample collection
At the end of the feeding phase the lambs were transported 150 km
to a commercial abattoir for slaughter after an overnight fast with water
available in lairage. All carcasses were trimmed according to AUS-MEAT
specifications (Anonymous, 2005) and were chilled at a mean temperature of 2 °C for 24 h. Muscle pH was measured at 24 h post-mortem, in
the m. longissimus lumborum (LL) using a pH metre with temperature
compensation (WP-80, TPS Pty Ltd., Brisbane, Australia) and a polypropylene spear-type gel electrode (Ionode IJ 44), calibrated at chiller temperature. The LL from the lumbar region was removed from the left side
of the carcass and cut in half. From the cranial end, duplicate samples
(~25 g) were collected (11th rib area) with one set stored at −80 °C
for subsequent determination of antioxidant status (vitamin E) and
the other at −20 °C for determination of fatty acid composition. The remaining section of the LL samples was used for the assessment of fresh
colour stability over 4 days of retail display (i.e., 5 days post-slaughter)
and determination of lipid oxidative substances (thiobarbituric acid reactive substances, TBARS).