Title: Correlations between measures of feed efficiency and feedlot return for F1 lambs Authors
Submitted to: Western Section of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 1, 2011
Publication Date: June 1, 2011
Citation: Kirschten, D.P., Notter, D.P., Leeds, T.D., Mousel, M.R., Taylor, J.B., Lewis, G.S. 2011. Correlations between measures of feed efficiency and feedlot return for F1 lambs. Western Section of Animal Science Proceedings. 62:86-89. 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 feedlot return for progeny of terminal-sire breeds of sheep are needed to improve lamb profitability. Thus, we used recent economic data to determine the effects of terminal-sire breed on returns of F1 lambs. Annually for 3 yr, Columbia, USMARC Composite, Suffolk, and Texel rams were mated with mature Rambouillet ewes. From weaning until harvest, F1 lambs (561 wethers; 548 ewes) were fed a step-up finishing diet for ad libitum intake. Pen was the experimental unit, with 3 pens of lambs per year for each sex and sire breed and 1 self feeder per pen. 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). Feed intake (FI), BW gain, G:F, feed conversion (FC), residual feed intake (RFI), residual BW gain (RGN), and feedlot return ($R) were determined. Return was based on 2010 Idaho feeder and slaughter lamb prices, feed costs, and other typical costs; no discounts were applied for excessively fat lambs. Year and breed, but not sex, affected (P < 0.01) $R. The $R for Suffolk-sired ($38.15) was greater than that for Columbia- ($28.49) and Texel-sired ($27.22), but not different from $R for Composite-sired lambs ($32.54). Pearson correlations between $R and BW gain, G:F, and FC were 0.76, 0.85, and -0.84, respectively (P < 0.01). Correlations were not significant between $R and RFI (P > 0.76), RGN (P > 0.10), and FI (P > 0.39). Even though BW gain accounted for less variation in $R than did G:F and FC, BW gain does not require measurement of FI, which is not typically measured in the industry. Selecting terminal-sire breeds with increased genetic merit for postweaning BW gain should simultaneously improve returns from feedlot lambs.