Small Ruminant: Production and Reproduction

Scientific data for carcass traits of terminal-sire sheep breeds can be used to improve the value of market lambs, but information is lacking for modern terminal-sire breeds in the United States. Thus, the effects of terminal-sire breed on 14 fabricated carcass measurements were determined in F1 wether lambs. Columbia, USMARC-Composite (Composite), Suffolk, and Texel rams were mated with mature Rambouillet ewes over 3 yr. From weaning until harvest each year, F1 lambs (n = 518) were fed a step-up finishing diet and harvested in 3 groups at targeted mean BW of 54.5, 61.4, or 68.2 kg. Carcasses were fabricated according to Style A of Institutional Meat Purchase Specifications. Weights were collected for the following carcass subprimal cuts: neck, foreshank, breast, square-cut shoulder (SCShoulder), rack, roast ready rack (RRR), loin, trimmed loin (TLoin), sirloin, boneless sirloin (BSirloin), flank, leg, boneless leg (BLeg), and hindshank. All traits were analyzed individually with a mixed model that included fixed effects of sire breed, year of harvest (YR), harvest group (HG), weight-on-test deviation from the breed mean, and random effects of sire and maternal grandsire. The YR and HG were significant (P < 0.01) in all models. Sire breed was significant (P < 0.01) for all traits except flank (P = 0.05). Suffolk-sired lambs had the heaviest neck (0.86 kg), breast (4.1 kg), SCShoulder (6.5 kg), rack (3.4 kg), RRR (1.5 kg), loin (3.2 kg), sirloin (3.1 kg), leg (10.6 kg), and BLeg (4.6 kg) compared with the other F1 lambs. Suffolk-sired lambs had the heaviest foreshanks (1.7 kg) and TLoin (2.7 kg); then Columbia-sired, 1.5 and 2.6 kg, respectively; and Texel-sired lambs had the lightest, 1.4 and 2.4 kg, respectively. Suffolk-sired lambs had heavier BSirloin (1.7 kg) than Composite-sired lambs (1.5 kg), but Suffolkand Compositedid not differ from Texel(1.6 kg) or Columbia-sired (1.6 kg) lambs. Columbiaand Suffolk-sired lambs had heavier hindshanks than Texel-sired lambs, 0.94, 0.97, and 0.88 kg, respectively. Producers can use data such as these to select a terminal-sire breed of sheep that will improve the carcass value of market lambs.