Submitted to: Western Section of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 14, 2011
Publication Date: June 1, 2011
Repository URL: http://www.asas.org/westernsection/2011/proceedings/00000081.pdf
Citation: Kirschten, D.P., Notter, D.R., Leeds, T.D., Mousel, M.R., Taylor, J.B., Lewis, G.S. 2011. Feed intake and efficiency of F1 lambs. Western Section of Animal Science Proceedings. 62:81-85. 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: Objective estimates of feed efficiency for progeny of terminal-sire breeds of sheep are needed to improve the value of market lambs. Because recent terminal-sire breed-comparison data are lacking, we determined effects of terminal-sire breed on feed efficiency of F1 lambs. Each year for 3 yr, Columbia, USMARC Composite, Suffolk, and Texel rams were mated with mature Rambouillet ewes. From weaning until harvest each year, F1 lambs (561 wethers; 548 ewes) were fed a step-up finishing diet for ad libitum intake. Pen was the experimental unit, with 1 self feeder per pen. There were 3 pens per year for each sex and each sire breed. Measured amounts of feed were delivered weekly or biweekly; feed remaining at the end of each period was removed and weighed. Days on feed varied across years (84 to 105 d). Dry matter intake, BW gain, G:F, feed conversion (FC), residual feed intake (RFI), and residual BW gain (RGN) were measured or calculated. General linear models, with sire breed, year, and sex as fixed effects, were used to analyze all traits. Year was significant in all models (P < 0.01). Sex affected (P < 0.03) DMI and FC, tended to affect G:F (P < 0.07), but did not affect any other traits. The DMI was greatest (P < 0.01; 156.9 kg) for Suffolk-sired, least (137.6 kg) for Texel-sired, and intermediate (145.7 kg) for Columbia- and Composite-sired lambs. Gain in BW was greatest (P < 0.01) for Suffolk-sired lambs (27.7 vs. 23.8 kg for all other sire breeds). Compared with other sire breeds, FC was least (P < 0.03) and G:F was greatest (P < 0.02) for Suffolk-sired lambs (FC, 5.8 vs. 6.2 kg of DMI/kg of gain; G:F, 0.177 vs. 0.167 kg of gain/kg of DMI). Breed did not affect RFI. The RGN for Suffolk-sired was greater (P < 0.02; 1.5 kg) than RGN (-0.5 kg) for Columbia- and Composite-sired lambs; RGN (-0.3 kg) for Texel-sired lambs did not differ from of any of the others. Producers can use these results to select a terminal-sire breed to improve the value of their market lambs.