Submitted to: American Society of Animal Science Annual Meeting
Publication Type: Abstract only
Publication Acceptance Date: 3/1/2011
Publication Date: 6/15/2011
Citation: Mousel, M.R., Leeds, T.D., Notter, D.R., Zerby, H.N., Moeller, S.J., Lewis, G.S. 2011. Carcass fat and muscle measurements in terminally sired F1 lambs. American Society of Animal Science Annual Meeting. 89:584. Interpretive Summary: Terminal sire breed can affect final body weight and carcass composition of crossbred lambs. Scientists at the U.S. Sheep Experiment Station determined whether breed of terminal sire affected final live lamb weight, chilled carcass weight, carcass loin muscle area, carcass back fat, carcass body wall thickness, and weight of kidney-pelvic fat. All of these traits are important determinants of carcass value. Terminal-sire rams, Columbia, USMARC Composite, Suffolk, and Texel, were mated to mature Rambouillet ewes over a period of three years to produce 518 wether lambs. Lambs were finished in a feedlot to a targeted average weight of 54.5, 61.4, or 68.2 kg. Live body weight was measured before the lambs were shipped to the abattoir. The Suffolk-sired lambs had heavier final live, chilled carcass, and kidney-pelvic fat weights than did lambs of the other three sire breeds. The Texel- and Suffolk-sired lambs had larger loin muscle areas than did the other two sire breeds. Breed differences were not detected for back fat or body wall thickness. The results from this study indicate that producers can select a terminal-sire breed to improve the value of their market lambs.
Technical Abstract: Science-based data for growth and carcass traits of terminal-sire breeds of sheep can be used to improve the value of market lambs, but information for modern terminal-sire breeds in the United States is limited. Thus, the effects of terminal-sire breed on live weight, chilled carcass weight, loin muscle area, and 3 measures of fat were determined in F1 wether lambs. Over a 3-yr period, Columbia, USMARC Composite, Suffolk, and Texel rams were mated with mature Rambouillet ewes. From weaning until harvest each year, the 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. Lamb BW was measured before transport to the abattoir. The following traits were measured on each carcass: kidney pelvic fat (KPF), chilled carcass weight (CCW), 12th and 13th rib loin muscle area (LMA), backfat thickness (BF), and body wall thickness (BWT; approximately 12.7 cm ventral to the dorsal midline). All traits were analyzed with mixed models 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 < 0.03) in all models. Sire breed was significant (P < 0.03) for all traits except BF (P > 0.09) and BWT (P > 0.06). Suffolk-sired lambs had the largest BW and CCW, 65.66 and 32.56 kg, respectively, and Texel-sired lambs had the smallest, 59.43 and 29.06 kg, respectively. Suffolk-sired lambs had the most KPF, 1.29 kg, and Columbia-sired lambs had the least, 1.13 kg. Texel- and Suffolk-sired lambs tended to have the greatest BF and BWT, while Columbia-sired lambs tended to have the least. The LMA for Suffolk- and Texel-sired lambs was greater than that for Columbia- and Composite-sired lambs, 17.05, 16.79, 15.47, and 16.049 cm2, respectively. Producers can use data such as these to select a terminal-sire breed of sheep that will match their production system and improve the value of their market lambs.