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Prediction of Genetic Differences Among Herds with Estimates of Breeding Value¹

Department of Animal Science, Iowa State University, Ames 50011

ABSTRACT

Estimates of breeding values are used to select cows across herds as well as within herds to be dams of future sires. Variation in estimates of breeding values should reflect genetic differences among cows, among and within herds. This study compared the amount of genetic differences among herds predicted by six estimates of breeding values.

Estimates of breeding values were developed by selection index and a mixed linear model for 25,843 Holstein cows in 693 herds in Iowa, Kansas, and Missouri. Intrasire regressions indicated that 10% of the differences among herds was genetic. Additional regressions indicated that the estimates of breeding value varied significantly in their ability to predict these genetic differences, but even the best procedure yielded estimates less than 60% of the desired value. Both inclusion of more information from relatives and adjustment of herdmate averages for expected herd genetic average improved the association of herd production with estimates of breeding values. Estimates of breeding values did not vary greatly in the proportion of their total variation associated with herds. Product-moment correlations between the estimates of breeding values were all greater than .88.

¹ Journal Paper No. J-9114 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 1053. This work was supported partly by a grant from the National Association of Animal Breeders.