This study describes the impact of Australian Sheep Breeding Values (ASBV) for post-weaning weight (PWWT), C-site fatness (PFAT) and eye muscle depth (PEMD) on lamb carcasses within the Australian Sheep Industry CRC Information Nucleus Flock. These results are taken from the 2007 drop progeny, consisting of ~2000 lambs slaughtered at a target weight of 21.5 kg. These lambs were the progeny of sires selected to ensure genetic diversity across various production traits. As expected, the PWWT ASBV increased weight at slaughter, and hot standard carcass weight. Dressing percentage was markedly improved by increasing PEMD ASBV, thus prime lamb producers will be maintaining an animal of similar weight on farm, but delivering a markedly larger carcass at slaughter. Lean meat yield % (LMY%) was highest in the progeny of sires with low PFAT ASBV, which decreased whole carcass fatness and increased muscularity. PWWT ASBV affected carcass composition but had little impact on LMY%, as the decreased fatness was largely offset by increased bone, with relatively little change in muscle content. Lastly, PEMD ASBV had little impact on whole carcass LMY%, but did appear to cause some level of muscle redistribution to the higher value loin cuts, in turn increasing the value of the carcass lean.

Remote drafting technology is now available for sheep and will enable targeted supplementation of individuals grazing together as a flock in extensive rangeland systems. A system of supplementation in which sheep are given free access to supplement at a set time interval has not been studied previously. More information on animal behaviour and supplement intake is required so that this system can be used to meet animal growth targets. The experiment reported in this paper examined the relationship between frequency of access to supplements and rate of weight change of sheep. One hundred and forty 13 month old Merino wethers had free access to drinking water and poor quality hay in an enclosed area and were allowed access to either lupins or whole cottonseed at four different frequencies (0, 1, 2 or 7 d per week). No water was available in the areas containing lupins or cottonseed but one-way flow gates allowed animals to return to the main feeding area where hay and drinking water was available. Weight change was measured over 6 weeks. There was a linear response in growth rate to increased frequency of access to lupins, with each additional day of access increasing liveweight gain by 25.8 g/d. Access to whole cottonseed did not result in a significant difference in growth rate compared to the control animals. It is concluded that the response relationship for lupin feeding could be used to predict the frequency of access to supplement through remote drafting units, to meet animal weight change targets.