Use of multinational data to improve national evaluations of Holstein bulls.

The usefulness of multinational data for the improvement of national estimates of genetic merit of Holstein bulls was assessed. For 222 bulls, combined US-Canadian evaluations and evaluations from the US only from January 1993 for milk, fat, and protein yields were compared with their US only evaluations from August 1997. The correlations between the 1993 and 1997 evaluations and the standard deviations of differences in evaluations from added data favored the evaluations from the US only because of a part-whole relationship; often 1997 data were largely from US only data from 1993. However, the results for 35 bulls with reliability increases of > 5% indicated that combining US and Canadian evaluations improved the prediction of future evaluations. The value of foreign data also was assessed from national and international evaluations on the scales of Canada, Germany, and the US. The changes from 1996 national evaluations to either 1996 international evaluations or 1997 national evaluations were compared to determine whether adding international data at the earlier time could provide a useful prediction of subsequent change in national evaluations. Although the degree of agreement among differences from added national and international data varied, international evaluations did provide useful information beyond the more limited national data available at the same time.