Abstract:
In three experiments, we studied the effects of duration of rest and nature of resting conditions before slaughter and of electrical stimulation, on carcass weight, bruising and muscle properties of cattle of known age. In experiment 1, 22 Droughtmaster steers (mean liveweight 284 kg) rested for 2.5 or 26.5 h following a 125 km road journey. In experiment 2, 82 Zebu crossbred cows (mean liveweight 416 kg) rested for 4 or 52 h after a 1310 km rail journey. Those rested for 52 h were allowed to rest either peacefully (P), subjected periodically to noise and disturbances (D) or mixed with unfamiliar cows (M). In experiment 3, 68 Hereford and Simmental x Hereford cows (mean liveweight 445 kg) rested for 28 h, after a 930 km road and rail journey, and during this time were subjected to resting treatments P, D or M. All cattle had access to water until slaughter, and were slaughtered at the same abattoir. All carcasses were electrically stimulated in experiment 1, but only half those in each treatment group in experiments 2 and 3. Electrical stimulation of carcasses had a much greater effect on tenderness than did resting conditions before slaughter. The LD muscles of stimulated carcasses were more tender than those of unstimulated ones. Of the 31 cattle slaughtered after a few hours' rest, only one carcass had a high pH value 24 h post mortem. The LD muscles of cattle rested for 26.5 h were more tender than those of cattle rested for 2.5 h. Resting treatment did not consistently affect mean carcass weight, pH24, time for LD muscle to cool to 20�_C or cooking loss. Noise and disturbance during the resting period appeared to be more stressful than mixing (13.6 v. 4.5% carcasses with high muscle pH 24 h post mortem in experiment 3 only). Steers rested for 26.5 h had a higher mean bruise score than those rested for only 2.5 h, but there was no effect of resting time or resting conditions on bruising in cows.