Sire by Region Interaction for Production Traits in Dairy Cattle

Abstract

During the past decade considerable attention has been given to sire by herd interactions, but data have not been available to consider the broader regional aspects of this problem. Sire by region interactions for milk production, fat production, and fat test were examined, utilizing the first available DHIA record of 10,548 artificially sired daughters of 46 Holstein sires used in the northern and southern regions of the United States. Daughter records were expressed as deviations from adjusted herd-mate averages. Correlations between the average breeding values of the sires in the two regions for the three traits approached 1.00, indicating that the ranking of sires was essentially the same in both regions. Estimates of the sire by region interaction variances for the three traits also were essentially zero. Although additional confirmation is needed, these results suggest that influences associated with a particular region should not unduly confuse the ranking of sires in the different regions when herd-mate comparisons from artificially sired daughters are used.