Production systems to deliver premium grade lambs to the growing international and Australian markets

Abstract

This study investigated the potential to produce premium grade (>22kg carcass weight and fat score 2–4 [10–20mm GR range]) Australian lambs using feeds available in late spring to summer to meet a growing demand from growing international and local markets. Second cross lambs (Poll Dorset×[Border Leicester×Merino]) were fed either: lucerne pasture (Lucerne, Medicago sativa L.); annual ryegrass (Lolium rigidum Gaud.) with sub-clover pasture (Trifolium subterranean L.) (Ryegrass); a combination of annual ryegrass based pasture and a commercial finisher pellet (RyeFeedlot) or a commercial finisher pellet (Feedlot). Lambs were weaned, adapted to diet for 2 weeks and fed for a further 6 weeks. For the RyeFeedlot treatment, pellets were offered at 300g/day/head from week 1–4 and then at 500g/day/head from week 5–8. After 8 weeks of feeding, lambs were transported to a commercial abattoir, slaughtered and carcass traits assessed. Chemical analyses of the feedstuffs showed, estimated metabolisable energy (ME) concentration was highest for the Feedlot ration, intermediate for RyeFeedlot and Ryegrass and lowest for Lucerne, while crude protein (CP) concentration was highest for Lucerne, intermediate for Feedlot and lowest for RyeFeedlot and Ryegrass. Despite lower (P <0.05) DMI, ME and CP intake, lambs on the Ryegrass treatment grew faster (P <0.05), achieved heavier body weight (P <0.04) and carcass weight (P <0.002) than RyeFeedlot fed lambs. Feed efficiency (feed per gain) was higher (P <0.001) for Ryegrass and Lucerne than for Feedlot and RyeFeedlot treatments. Daily DM and ME intakes were greater (P <0.05) for lambs offered the Feedlot treatment than those fed the Lucerne treatment, but carcass weights and carcass yield (dressing%) did not differ between these groups. Carcass weight (P <0.002) was lowest for lambs offered the RyeFeedlot treatment compared with all other groups. Dressing percentage was higher (P <0.001) for lambs fed Lucerne and Feedlot treatments compared with lambs fed RyeFeedlot and Ryegrass treatments. On average, lambs from the RyeFeedlot treatment produced carcasses suitable for the lighter end of the local market (18kg), while Feedlot and Lucerne treatments produced carcasses suitable for export markets (22kg), however lambs fed the Ryegrass treatment produced carcasses with >18kg but less than 22kg required for the Australian national market. The number of lambs reaching 22kg carcass weight was 63, 54, 44 and 9% for Lucerne, Feedlot, Ryegrass and RyeFeedlot treatments, respectively and 0, 8, 0 and 22%, respectively were below 18kg. The results demonstrate that lucerne based pastures have the potential to consistently produce premium grade carcasses for growing export and local markets similar to feedlot rations.