Submitted to: Joint Abstracts of the American Dairy Science and Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2012
Publication Date: N/A
Interpretive Summary: Modern genetic technologies can be used to enhance the inherent abilities of lambs to convert livestock feed into human foods. Enhancing these inherent abilities would allow producers to conserve feed and natural resources, improve the value of their market lambs, and increase the efficiency of producing human foods. Thus, genetics studies are underway at the USDA, Agricultural Research Service, U.S. Sheep Experiment Station to characterize the effects of breed, which is composed of animals with common ancestors and certain distinguishable characteristics, including genetic makeup, of sire on various aspects of growth and carcass merit of lambs. Recent results from these studies indicate that breed of sire has important and predictable effects on carcass traits. Sheep producers can use this information to select sire breeds to make significant improvements in the efficiency of producing human foods.
Technical Abstract: 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 a 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 foreshank (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 Suffolk- and Composite- did not differ from Texel- (1.6 kg) or Columbia-sired (1.6 kg) lambs. Columbia- and 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.