Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/14/2012
Publication Date: 3/9/2012
Citation: Mousel, M.R., Notter, D.R., Leeds, T.D., Zerby, H.N., Moeller, S.J., Lewis, G.S. 2012. Evaluation of Columbia, USMARC-Composite, Suffolk, and Texel rams as terminal sires in an extensive rangeland production system: III. Prefabrication carcass traits and organ. Journal of Animal Science. DOI:10.2527/jas.2011-4767. 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: To evaluate terminal sire breeds, harvest BW, prefabrication carcass measurements, and organ weights were evaluated over 3 yr, for 518 crossbred wether lambs. Lambs were produced by single-sire matings of 22 Columbia, 22 USMARC-Composite (Composite), 21 Suffolk, and 17 Texel rams to adult Rambouillet ewes. Lambs were raised to weaning under an extensive western rangeland production system and finished in a feedlot on a high-energy finishing diet. Wethers were randomly assigned to be harvested at an average BW of 54.4, 61.2, or 68.0 kg and then transported to The Ohio State University abattoir for harvest. Wether BW was recorded before transport and before harvest. Prefabrication carcass measurements and organ weights were recorded either after harvest or after an approximate 24-h chill. Suffolk-sired lambs had the heaviest off-test BW, harvest BW, HCW, chilled carcass weight (CCW), and kidney weights (P < 0.01) than lambs sired by the other breeds. Suffolk-sired lambs had more (P < 0.01) kidney-pelvic fat than did Columbia-sired lambs; Composite- and Texel-sired lambs were intermediate and did not differ (P > 0.06) from the other crossbred lambs. Texel- and Suffolk-sired lambs had larger LM area and greater conformation scores than Columbia-sired lambs (P < 0.03). Texel-sired lambs had greater (P < 0.01) body wall thickness, quality grades, and leg scores than Columbia-sired lambs. Composite- and Suffolk-sired lambs did not differ from each other or from lambs sired by any other breed for body wall thickness (P > 0.18) and were intermediate for quality grades and leg scores. Sire breed did not affect (P > 0.05) shipping shrink, dressing percentage, pelt weight, liver weight, and fat depth. Adjusting data to a comparable harvest BW or CCW modified sire breed rankings for some measurements. Texel-sired lambs were equal or superior to lambs sired by other breeds for HCW, CCW, dressing percentage, pelt weight, LM area, quality grade, and leg and conformation scores. However, Texel-sired lambs also had values for kidney-pelvic fat weight, fat depth and body wall thickness that were equal to or greater than those of lambs sired by the other breeds, thus indicating increased fatness at comparable BW. Producers can use these results to select terminal-sire sheep breeds that will complement their production system and improve market lamb value.