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Prediction Equations of Beef Cow Efficiency^1,2,3,

University of Wisconsin, Madison 53706

Abstract

Data from 107 beef (Hereford), dairy (Holstein) and beef x dairy cross cows and their calves through three parities were used to develop prediction equations of cow efficiency. Efficiency was defined as the ratio of calf weaning weight output to cow and calf input through three parities, adjusted for age of the dam at completion of three parities. Cows and calves were individually fed in confinement. Prediction equations of weaning efficiency developed from these data were validated using data from South Dakota State University, and prediction equations developed there were validated using the Wisconsin data. Dam weight or weight:height ratio at weaning of the calf in combination with progeny weaning weight accounted for 56 and 59% of the variation in weaning efficiency, respectively. Equations based solely on traits measured early in the life of the cow were of less predictive value; yearling weight and weight:height ratio explained 22 and 25% of the variation in weaning efficiency, respectively. Equations using a measure of cow size or condition and progeny weight were the most parsimonius equations developed from both the Wisconsin and South Dakota data. These equations performed well when validated on independent data. However, yearling weight and weight:height of the dam, the best early traits for prediction of efficiency in the Wisconsin data, accounted for less than 1% of the variation in weaning efficiency in the South Dakota data.

¹ Dept. of Meat and Anim. Sci. Paper No. 856. 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 for typing this manuscript and Messrs. E. Hoch, P. Bringle and J. Kane for their excellent technical assistance in conducting the experiments.

⁴ Dept. of Meat and Anim. Sci., Univ. of Wisconsin, Madison 53706.

⁵ Dept. of Anim. and Range Sci., South Dakota State Univ., Brookings 57007.