Effects of genotype and dietary forage to concentrate ratio during the finishing period on carcass characteristics and meat quality of lambs from hill sheep systems

The study investigated the effects of lamb genotype produced from hill floc ks on feed efficiency, carcass characteristics and meat quality in animals finished on either a high forage: concentrate ratio diet (HFC) or a low for age: concentrate ratio diet (LFC). Purebred Scottish Blackface (BXB) lambs were compared with Blue-Faced Leicester x Scottish Blackface (BLXB) and Tex el x Scottish Blackface (TXB) lambs. Purebred Cheviot (CXC), Suffolk x Chev iot (SXC) and Texel x Cheviot (TXC) lambs were also investigated. Lambs on the LFC diet were offered grass silage and concentrates mixed in the propor tion of 0.80 silage and 0.20 concentrates on a dry matter basis. The LFC di et consisted of 0.20 grass silage and 0.80 concentrates on a dry matter bas is. Representative lambs were slaughtered at the start of the experiment an d on reaching 38 and 46 kg live weight. Averaged over the two slaughter wei ghts, within the Blackface cross lambs, BXB had a lower liveweight gain (P < 0.01) than either BLXB or TXB (138,207 and 203 (S.E. 11.1) g/day, respect ively). Within the Cheviot cross lambs, CXC had a lower liveweight gain (P < 0.05) than SXC (188 v. 220 (S.E. 11.1) g/day), while SXC and TXC (204 g/d ay) had similar liveweight gains. Lambs on the LFC diet had a higher dressi ng proportion (P < 0.001) compared with lambs finished on the HFC diet (0.4 66 v. 0.434 (S.E. 0.0018) kg carcass per kg live weight). Averaged over the two slaughter weights BXB lambs had a lower (P < 0.05) dressing proportion than the other genotypes. Carcass conformation classification (assessed on a five-point scale) was higher (P < 0.001) in lambs finished on the LFC di et (3.0 v. 2.4 (S.E. 0.04)). Conformation classification was higher in lamb s produced from Cheviot compared with Blackface ewes (P < 0.05). Within the Blackface cross lambs, BXB and BLXB lambs had a lower conformation classif ication (P < 0.001) than TXB lambs (2.4, 2.4 and 2.9 (S.E. 0.08) respective ly). Within the Cheviot ewes, TXC lambs had a higher (P < 0.001) classifica tion than either CXC or SXC (3.1, 2.7 and 2.7 (S.E. 0.08) respectively). La mbs finished on the LFC diet had a higher fat classification score compared with lambs on the HFC diet (P < 0.001) (3.4 v. 2.8 (S.E. 0.04)). Fat class ification was similar across all genotypes. Lambs finished on the LFC diet had a lower ash content in the carcass than lambs finished on a HFC diet (P < 0.01) (44 v. 47 (S.E. 0.8) g/kg). Lamb genotype and dietary forage: conc entrate ratio had no significant effect on cooking loss, sarcomere length, Warner-Bratzler shear force and L* values. Ultimate pH (pH(U)) was not infl uenced by dietary forage: concentrate ratio, but was significantly (P < 0.0 1) higher in BXB lambs compared with BLXB, TXB, CXC and TXC lambs. Lambs of fered the LFC diet during the finishing period had significantly higher val ues for a* (P < 0.05), b* (P < 0.001), C* (P < 0.001) and HI (P < 0.05) tha n lambs offered a HFC diet. Of these parameters only b* was significantly a ffected by lamb genotype, with BXB lambs having a lower value (P < 0.05) th an the other genotypes.