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Life Cycle Efficiency of Beef Production: VII. Prediction of Cow Efficiency Ratios for Progeny Weaned and Slaughtered^1,2,3,

University of Wisconsin, Madison 53706 and U.S. Department of Agriculture, Clay Center, NE 68933

Abstract

Weight and individual feed consumption data collected on 160 beef, dairy and beef x dairy dams and their progeny were used to calculate several measures of life cycle and actual lifetime cow efficiency to weaning and slaughter end points. Accuracy of predictors of cow efficiency that did not require feed intake data for progeny or dams was then examined. Multiple coefficients of determination (R²) for predictors expressed as the ratio of weaning or slaughter weight output to dam weight were similar to those for predictors expressed as the ratio of weight output to metabolic weight of dam. Including progeny metabolic weight along with dam metabolic weight in the denominator of ratio predictors generally reduced R² values. Accuracy of prediction was lower for weaning or slaughter weight alone than for predictors that expressed progeny weight as a ratio to dam weight or dam metabolic weight. The R² values were greater for multiple regression equations that included combinations of progeny weight, dam weight, weight:height ratio of dam, milk production and age of dam at calving than for ratios of progeny and dam weights. A prediction equation that included progeny weaning or slaughter weight, dam weight and age of dam at calving was the most useful from the standpoint of accuracy and simplicity. Life cycle and actual lifetime efficiency were predicted with sufficient accuracy to be useful (R² >.30) at the end of the second parity in all analyses.

¹ Dept. of Meat and Anim. Sci. Paper No. 858. Research was supported by the College of Agr. and Life Sci., Univ. of Wisconsin, Madison, and the Agr. Res. Serv., USDA. Semen was donated by Amet. Breeders Serv., DeForest, WI; Amer. Int. Charolais Assoc., Houston, TX; Carnation Genetics, Hughson, CA; Curtiss Breeding Serv., Cary, IL; East Central Breeders Coop., Waupun, WI; Midwest Breeders Coop., Shawano, WI; Noba, Inc., Tiffin, OH; and Tri-State Breeders Coop., Westby, WI.

² The experiments were contributions to North Central Regional Project NC-1, "Improvement of Beef Cattle Through Breeding Methods."

³ The authors thank E. Hoch, P. Bringle and J. Kane for their excellent technical assistance in conducting the experiments.

⁴ Present address: Anim. Sci. Dept., The Ohio State Univ., Columbus 43210.

⁵ Dept. of Meat and Anim. Sci., Univ. of Wisconsin, Madison 53706.

⁶ Roman L. Hruska, U.S. Meat Anim. Res. Center, ARS, USDA, Clay Center, NE 68933.

⁷ Graduate research associate, Anim. Sci. Dept., The Ohio State Univ., Columbus 43210.