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Title: Evaluation of Columbia, USMARC-Composite, Suffolk, and Texel rams as terminal sires in an extensive rangeland production system: IV. Postweaning growth, feed intake, and feed efficiency

Author
item Kirschten, David
item NOTTER, DAVID - Virginia Polytechnic Institution & State University
item Leeds, Timothy - Tim
item Mousel, Michelle
item Taylor, Joshua - Bret
item Lewis, Gregory

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2013
Publication Date: 5/22/2013
Citation: Kirschten, D.P., Notter, D.R., Leeds, T.D., Mousel, M.R., Taylor, J.B., Lewis, G.S. 2013. Evaluation of Columbia, USMARC-Composite, Suffolk, and Texel rams as terminal sires in an extensive rangeland production system: V. Postweaning growth, feed intake, and feed efficiency. Journal of Animal Science. 91(5):2021-2033.

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 postweaning weight gain, feed intake, and feed efficiency. Sheep producers can use this information to select sire breeds to make significant improvements in the efficiency of producing human foods.

Technical Abstract: This study was conducted to quantify differences in postweaning performance among 4 sire breeds using records from 1,109 crossbred lambs over 3 yr. Lambs were sired by Columbia, USMARC-Composite (Composite), Suffolk, and Texel rams mated with adult Rambouillet ewes. After weaning, lambs were finished on a high-energy diet in group-fed pens. Suffolk-sired lambs grew 13 to 19% faster (P < 0.05) and were 7 to 15% heavier (P < 0.05) after 90 d than the other breed crosses, and Suffolk-sired lambs consumed 4 to 11% more (P < 0.01) ME. However, the G:F at 90 d was greater (P < 0.01) for Suffolk-sired lambs (5.99 vs. 5.62 g of BW gain/ME intake, Mcal) than for the other 3 sire breeds. Suffolk-sired lambs had the greatest (P < 0.05) residual BW gain (RG) at 90 d (0.94 vs. - 0.32 kg BW for the other 3 sire breeds combined), and at 6.6 (0.63 vs. - 0.24 kg of BW for the other sire breeds combined) and 9.1 mm of fat depth (0.87 vs. - 0.32 kg of BW for the other sire breeds combined). At 60 kg of BW, Suffolk-sired lambs had eaten 16 to 24% less (P < 0.01) than the other breed crosses. Suffolk-sired had greater (P < 0.05) RG (0.73 kg of BW) than Composite- and Columbia-sired (- 0.44 kg of BW combined) at 60 kg of BW, but Suffolk- were not different (P > 0.05) from Texel-sired lambs (0.00 kg of BW). Suffolk-sired lambs had the greatest (P < 0.05) RG at 90 d, Columbia-sired lambs had the greatest (P < 0.05) residual feed intake (RFI; 7.02 vs. - 2.53 Mcal ME for the 3 other sire breeds), and Texel-sired lambs ate 5 to 11% less ME (P < 0.01) than the other breed crosses. At 60 kg of BW, Texel- and Composite- (- 2.34 Mcal, ME combined) had more favorable (P < 0.05) RFI than Columbia- (6.45 Mcal, ME), and Suffolk-sired lambs (0.44 Mcal, ME) were intermediate and not different from the other 3 sire breeds. At 6.6 mm of fat depth, Columbia- and Suffolk- (3.28 Mcal, ME, combined) had greater (P < 0.05) RFI than Texel-sired lambs (- 4.23 Mcal, ME); at 9.1 mm of fat depth, Columbia-sired lambs had the greatest (P < 0.05) RFI (7.36 vs. - 2.12 Mcal, ME for the other breeds combined). In summary, except for ME intake at 90 d, Suffolk-sired lambs were equal or superior to Columbia-, Composite-, and Texel-sired lambs for BW, BW gain, ME intake, G:F, RFI, and RG to 90 d, 60 kg of BW, and 9.1 mm of fat depth. Also, terminal sire breed affected G:F, RG, and RFI, and breed ranks for RFI changed across the test period, but breed ranks did not change for G:F and RG.