Characteristics of lamb carcasses of contrasting subjective muscularity

In order to compare characteristics of lamb carcasses with superior muscularity (the European E class) with carcasses that did not fit the E specification, 114 E carcasses were individually matched for weight and fatness class with 114 Non-E carcasses. The carcasses (mean weight = 17 kg) were processed under commercial conditions into six trimmed, boneless cuts of the leg and saddle (inside, outside, knuckle, rump, striploin and tenderloin) and two bone-in cuts (hind-shank and 7-rib rack). After adjustment for carcass weight, fatness (as assessed by fat depth C and tissue depth GR) and sex, the E-class group, relative to the Non-E group, had a 4.3% higher yield of leg and saddle cuts, a 14.2% higher leg muscularity index calculated from the weights of trimmed boneless cuts around the femur and femur length, a 13.6% higher muscle to bone ratio in the femur region, an 8.2% greater 'eye'-muscle depth (B), and a 3.7% greater 'eye'-muscle width (A) (all P < 0.001). All boneless cuts except the knuckle were heavier for the E group. Carcasses of female lambs had legs with higher muscle to bone ratios and a higher yield from the leg plus saddle (both P < 0.01), but the muscularity index was similar between sexes. It is concluded that although lamb carcasses subjectively selected as having higher muscularity will yield slightly more meat, this difference will be small compared with the greater muscle depth relative to bone length. The importance consumers attach to carcass or cut shape over and above any association with meat yield needs to be assessed.