Objective measurement of shear force revealed no difference between genotypes for
tenderness, whether measured on the loin or the topside (Experiment 2). There was no
evidence of a curvilinear relationship between pH and tenderness of the loin (Purchas,
1990; Young et al., 1993), although we had few samples with high pH values.
There is much anecdotal evidence from industry that Merino lambs produce darker
meat than crossbred lambs. Young et al. (1993) suggested, that Merino lambs in
New Zealand may produce darker cooked meat, but they did not measure meat colour
in the raw state. Our results showed no differences in objectively measured colour of
muscles between the genotypes when they were raised and slaughtered under the same
conditions. Darker meat may have been expected from the BL x M and M x M genotypes
because of their higher pH, although Menzies and Hopkins (1996) found a poor correlation
between pH and objectively measured colour across a pH range of 534 to 6.11. In
Australia, Merino lambs commonly graze low quality pastures and are generally slower
growing and older than crossbred lambs at slaughter. These environmental factors may
lead to meat colour differences between genotypes which are not due an intrinsic breed
effect.