Animal performance and chemical body composition of lambs fed diets with different protein supplements

Abstract

Thirty six Merino lambs with average initial live weight of 13.5 kg (SE ± 0.56 kg) were used in a 3×3 factorial arrangement (4 lambs per group). The treatments were three concentrate supplements (barley [B], barley 82.5% plus soybean meal 14.5% [BSM] and barley 82.5% plus meat meal 14.5% [BMM]) and three slaughter weights (20, 25 and 30 kg live weight). The lambs fed the B diet consumed less concentrate supplement (0.701 vs. 0.780b and 0.758b kg DM day−1, P<0.05) gained weight less rapidly (217 vs. 304b and 304b g day−1, P<0.01) and had a greater food conversion ratio (3.29 vs. 2.64b and 2.57b g DM supplement kg−1 LW gain, P<0.01) than the lambs on the BSM and BMM treatments respectively. Lambs supplemented with B were characterised by the highest fat and energy deposition (P<0.01) in both components of the empty body weight (carcass and ‘non-carcass'). Although diet protein concentrations were different between supplements (B: 165.5, BSM: 219.3 and BMM: 237.2 g kg−1 DM), there were no differences (P>0.05) in crude protein intake between BSM and BMM. (171.0 vs. 179.7 g crude protein day−1). The source of dietary protein (soybean meal vs. meat meal) did not have a significant influence (P>0.05) on performance and chemical body composition of lambs. The interactions between the effect of slaughter weight and the concentrate supplement were non-significant (P>0.05). This study suggests that meat meal can successfully replace soybean meal as a protein supplement for growing lambs from weaning to 30 kg live weight and offer an alternative to soybean meal as a regional protein source for lamb diets.