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Life Cycle Efficiency of Beef Production: V. Relationship of Cow Efficiency Ratios for Progeny Slaughtered to Components of Input and Output^1,2,3,

University of Wisconsin, Madison 53706 and US Department of Agriculture, Clay Center, NE 68933

Abstract

Several measures of life cycle cow efficiency were calculated using weights and individual feed consumptions of 160 beef, dairy and beef x dairy dams and their progeny. Ratios of output to input were used to estimate efficiency, where outputs included relative values for slaughter weights, carcass weights and trimmed wholesale cut weights of progeny and weight of the dam, and inputs included pre- and postweaning feed consumption of progeny plus feed consumed by the dam over her entire lifetime. In the first approach to estimating efficiency, inputs and outputs were weighted by their probability of occurrence, where probabilities were a function of the age distribution of the cow herd and calf crop percentage in a theoretical herd. The second approach involved dividing the sum of the weight outputs by the sum of the feed inputs when all pieces of information were weighted equally. Both approaches included efficiency estimates calculated with and without cow salvage value. Efficiency estimates that did not include salvage value of the dam were negatively correlated (P<.01) with weight of dam at weaning. Larger, faster-gaining progeny were more efficient in the time constant postweaning phases of experiments initiated in 1964, 1969 and 1974. Correlations of cow efficiency with slaughter weights of progeny summed across parities were positive and highly significant. Metabolizable energy (ME) intake of dams accounted for approximately 69 and 65% of the total ME required to produce slaughter progeny in the first and second approaches, respectively, and showed a large negative association with lifetime efficiency.

¹ Dept. of Meat and Anim. Sci. Paper No. 816. Research was supported by the College of Agricultural and Life Sciences, Univ. of Wisconsin, Madison, and the Agr. Res. Service, USDA. Semen was donated by American Breeders Service, DeForest, WI; American Int. Charolais Assoc., Houston, TX; Carnation Genetics, Hughson, CA; Curtiss Breeding Service, 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 wish to thank Ms. S. Kading and Ms. J. Busby for typing this manuscript and Messrs. 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, US Meat Animal Research Center, ARS, USDA, Clay Center, NE 68933.