The effects of pregnancy status (non-pregnant, early to mid (1 to 5 months) and late (> 6 months)) and month of pregnancy on live weight, carcass weight, dressing proportion, bruising and muscle properties were examined in 237 Shorthorn and Brahman crossbred cows (mean live weight 424 kg, 62% pregnant). The cows were transported 1155 km to an abattoir and given access to food and water until slaughter. Mustering to slaughter periods were 5, 6 or 7 days.
The mean gross hot carcass weights for the 89 non-pregnant, 108 early to mid pregnant and 40 late pregnant cows were 207, 199 and 187 kg (P < 0·05). Their respective dressing proportions were 487, 469 and 443 g/kg (P < 0·05). Among the pregnant cows, carcass weight and dressing proportion decreased by 2·95 kg and 6 g/kg, respectively, for each month of pregnancy (P < 0·05).
Cows in late pregnancy had lower mean initial yield (IY) and peak force (PF) shear values for m.longissimus dorsi (LD) than non-pregnant cows. The late-pregnant cows also had the greatest mean pH 24 h post mortem (pH24) and ultimate pH (pHu) values (P < 0·05). They also had a greater proportion of carcasses with high pHu values than the early to mid-pregnant and non-pregnant cows (0·30 v. 0·157 v. 0·079; (P < 005). Among the pregnant cows, mean pH24 increased by proportionately 0·038 and the proportion of high pH24 carcasses by 0·055 for each month of pregnancy (P < 0·05). Pregnancy status had no significant effect on mean fat depth, bruise score, PF-IY value or cooking loss.