Carcass quality of crossbred lambs expressing the callipyge phenotype bornto Romanov purebred and crossbred ewes

Carcass quality was evaluated in 35 male and 41 female lambs, 38 expressing the callipyge phenotype (Cg) and 38 controls expressing the normal phenoty pe (N). Lambs were from Romanov and Suffolk X Romanov ewes mated to two rui ns heterozygous for the callipyge locus and slaughtered at approximately 44 kg live weight. The Cg lambs reached slaughter weight at 163 days of age, 13 days younger, and had a dressing proportion 0.524, 0.029 points higher. Also they had more leg (341 v. 308 g/kg), less loin (315 v. 328 g/kg) and l ess shoulder (340 v. 360 g/kg) than the N lambs. The leg, loin and shoulder wholesale cuts and half the carcass of Cg lambs had 82, 113, 77, and 92 g/ kg more lean and 52, 98, 59, anti 72 g/kg less fat than N Iambs, respective ly. The Cg lambs also had larger loin-eye area (18.5 v. 13.1 cm(2)), less b ackfat at the C (4.1 v. 6.1 mm) and at the GR locations (11.0 v. 15.2 mm) a nd less internal fat (202 v. 339 g) than the N lambs. Dissection of the 12t h rib indicated that Cg lambs had more muscle (574 v. 462 g/kg), less fat ( 276 v. 358 g/kg) (both P < 0.001) and similar (P > 0.05) bone (155 v. 165 g /kg) to N lambs. Colour of the longissimus muscle was significantly paler i n Cg lambs. Intramuscular fat and dry matter of longissimus muscle were sig nificantly lower (49 v. 120 and 247 v. 253 g/kg) in Cg than in N lambs. Cg lambs were significantly different (P < 0.05) from N lambs for all traits s tudied except age at slaughter, tissues at the GX location, proportion of b one in the 12th rib and the L* colour of the longissimus muscle. Breed type effect was significant only for age at slaughter, whereas the effect of se x was significant for all traits except for proportion of lean in the leg, b* colour and intramuscular fat content of the longissimus muscle. No inter actions were significant except phenotype X breed type on fat thickness ove r the longissimus muscle. Post-mortem ageing of the longissimus muscle for 9 or 15 days caused a significant reduction in muscle toughness in Cg lambs compared with those aged for 3 days (113 v. 98 Newtons) but the muscle tea s still rougher than that from N lambs (with a shear force of 64 and 51 New tons 15 at 3 and 9 or 15 days post mortem). The principle component analysi s including carcass conformation and composition traits as well as meat qua lity traits was indicative of a distinctly different carcass of Cg compared with N lambs. The first two principal components explained 0.70 of the tot al variation.