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University of Wisconsin, Madison 53706 and US Department of Agriculture, Clay Center, NE 68933
Abstract
Weights and individual feed consumptions of 160 beef, dairy and beef x dairy dams and their progeny were used to estimate several measures of life cycle cow efficiency. Efficiency was expressed as the ratio of output to input, where output included relative values for slaughter weights, carcass weights and trimmed wholesale cut weights of progeny and weight of the dam, and inputs were pre- and postweaning feed consumption of progeny plus lifetime feed consumption of the dam. In the first approach, inputs and outputs were weighted by their probability of occurrence; 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. Weight, height and weight/height of dam at 240 d of age were not correlated significantly with subsequent efficiency of progeny slaughter weight production, indicating that selection on these traits would be ineffective for increasing lifetime cow efficiency. However, females exhibiting more efficient weight gains from 240 d to first calving tended to produce progeny with more efficient post-weaning gains and tended to become more efficient producers on a lifetime basis. Correlations of efficiency estimates with weight of dam at calving were negative and generally highly significant. Height of dam was related positively to postweaning feed efficiency of progeny, but was negatively related to life cycle cow efficiency. Correlations involving weight/height indicated that fatter dams were less efficient. Level of milk production needed to maximize biological efficiency varied with the breed combinations involved. The importance of fertility and calf survival were demonstrated by the close association of efficiency with slaughter rate and age at calving. Correlations among efficiency ratios calculated at weaning and at slaughter were .88 (P<.01) or above, whereas relationships between pre- and post-weaning efficiency were nonsignificant. Correlations between postweaning efficiency and efficiency of slaughter weight, carcass weight and trimmed wholesale cut weight production ranged from .10 (P>.05) to .41 (P<.01).
1 Dept. of Meat and Anim. Sci. Paper No. 847. 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.
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