Improving the pre- weaning nutrition of calves by supplementation of the cow and/or the calf while grazing low quality pastures - 2. Calf growth, carcass yield and eating quality

Tender, juicy and flavoursome are desirable meat traits in the grading syst em of Meat Standards Australia. There are 3 critical growth phases affectin g these traits in domestic trade cattle: birth to weaning (phase I), weanin g to feedlot entry (phase II), and feedlot finishing (phase III). In the st udy reported in this paper we examined the effects of supplementary feeding of cows and/or calves in phase I on calf growth rate during each of the 3 growth phases and assessed whether differences in early growth were recorde d in carcass weights and meat quality at slaughter (16.5 months old). The c alves were weaned on to high quality pastures (phase II) and then finished in a feedlot on a grain-based diet (phase III). One-hundred Hereford cows with Angus-sired calves, and 24 Hereford cows, wi th Hereford-sired calves were allocated to treatments in a 2 x 3 factorial study of calf growth rate during phase I. The treatments consisted of nil o r 4.2 kg twice-a-week of cottonseed meal to the cows for 145 days from calv ing to mid-lactation, and calves either had access to a high protein barley -based supplement in a 'creep' from 75, or from 150 days old until weaning. There were 4 replicate groups for each treatment during phase I with 24 pa ddocks. Weaners were grazed as a single herd during phase II of the study a nd separated into 10 feedlot pens in phase III. At slaughter, after phase I II, M. longissimus et laborum muscle was sampled from half the carcasses an d graded by a taste panel according to Meat Standards Australia. Calves, suckled by cottonseed meal-supplemented cows, were heavier at weani ng than those calves suckled by non-supplemented cows (201 v. 170 kg; phase I) with a trend for younger calves with access to 'creep' feeding (from 75 days old) to be heavier than calves without access to 'creep' feed (196 v. 175 kg). During phase II, liveweight change was higher for weaners from no n-supplemented cows than for weaners from supplemented cows (679 v. 593 g/d ay). During phase III this trend was reversed in favour of weaners from cot tonseed meal-supplemented cows (1.54 v. 1.46 kg/day). Similarly, carcasses of calves from cottonseed meal-supplemented cows were also heavier than oth er carcasses from other calves (226 v. 212 kg) with a greater depth of rib fat (7.0 v. 5.8 mm). In contrast to carcass weight, M. longissimus et labor um muscle samples from calves which did not have access to supplement durin g phase I were assessed as being more tender, more flavoursome and having a higher overall Meat Standards Australia score than M. longissimus et labor um muscle from calves that had access to supplements. The carryover effects of nutrition from the preweaning growth phase of calves highlight the impo rtance of early life nutrition for achieving higher carcass weights and mea t quality. However, the findings that M. longissimus et laborum samples fro m calves with lower growth rates before weaning were more tender and graded higher than samples from calves with higher growth rates was both unexpect ed and unexplained.