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Comparison of Alternative Models for Within-Herd Genetic Evaluation of Beef Cattle

University of California², Davis 95616

Abstract

Four models for within-herd sire evaluation were compared on 13 years data with 2,656 weaning weight records from a cooperating purebred Hereford herd. The alternative models studied considered sires related vs sires unrelated and sires in genetic groups vs ignoring groups.

The correlations among sire evaluations from the alternatives were high (r>.97), however, the prediction error variance for the young sires which are of primary interest decreased 10 to 22% due to considering sire relationships vs considering sires unrelated. This decrease was more evident in comparing models which ignore grouping sires.

Bias in the sire effect solutions due to ignoring groups was calculated in models with and without the sire relationships. The difference due to bias between sires from two different groups on the average approximates the corresponding difference in group solutions used to calculate the bias. That is, evaluations ignoring groups are not greatly different from the evaluations (sire solution plus group solution) when groups are considered. However, based on these data where differences in group effects and estimated biases were small it is not possible to generalize on the merits of using sire groups for within-herd genetic evaluation.

¹ Cooperative Extension, Department of Animal Science.

² Department of Animal Science.