Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 22, 1996
Publication Date: N/A
Interpretive Summary: Comparison of dairy bulls across countries has been difficult, controversial, and often of questionable accuracy. In February 1995, the International Bull Evaluation Service, which has 32 country members, produced the first large-scale international evaluations for Holsteins. The 54,781 bulls had evaluations for milk, fat, and protein expressed to the scale of each of the 9 countries (Canada, Denmark, Finland, France, Germany, Italy, Holland, Sweden, and the United States). The international rankings of bulls for a given country were examined and found to be essentially the same as for national evaluations. Thus, the combining of data did not alter within-country rankings. Most countries have used U.S. genetics extensively. Each country except Finland had U.S. sires for 75 to 99 of their top 100 bulls. This has resulted in reduction of U.S. superiority, although the United States still has the highest genetic average. Each country has their own economic index for combining milk, fat, and protein bull evaluations. Those indexes were compared. Although all appeared to be quite different, some ranked bulls almost the same. Others, however, ranked bulls quite differently. Having evaluations for bulls from many countries on the same scale will allow breeders to make more informed selection decisions. However, use of an index appropriate for their farm situation is essential to making the most progress.
Technical Abstract: Results of the first large-scale international genetic evaluation of Holstein bulls were examined. National evaluations were combined for Canada, Denmark, Finland, France, Germany, Italy, The Netherlands, Sweden, and the United States. The assumption of a genetic correlation of .995 between all countries and the exclusion of daughters of bulls from a country where not sampled resulted in correlations of essentially unity between sets of national and international evaluations. For the few bulls with daughters in multiple countries, correlations were lower but still high. Genetic trend was more rapid for countries where earlier genetic merit was lowest. Thus, difference among countries in genetic merit have reduced markedly, especially between the United States and others. The extensive use of U.S. sires in other countries has permitted a closing of the genetic gap. The average evaluation for bulls born in 1988 in the United States surpassed bulls in France, Italy, and The Netherlands by less than 3 kg for predicted transmitting ability for protein. Application of seven national indexes for combining yield data showed that some were similar in impact. Others reduced mean merit of the selected 100 bulls substantially, even more than half an index standard deviation. The index needs to be correct or progress can be reduced markedly. Changes in methodology for the international evaluations have already taken place, and future research needs to examine the impact of those modifications.