Examination of international genetic evaluations of Holstein bulls.

The first large-scale, international genetic evaluation of Holstein bulls computed by the International Bull Evaluation Service Centre in February 1995 was examined and compared with national evaluations from Canada, Denmark, Finland, France, Germany, Italy, Sweden, The Netherlands, and the US. Assumption of a genetic correlation of 0.995 between all countries and exclusion of bull daughters from a country in which the bull had not been sampled resulted in correlations of essentially unity between national and international evaluations. For the few bulls sampled in multiple countries, correlations were lower but still high (< or = 0.95). Genetic trend was more rapid for countries in which genetic merit for earlier years was lowest. Differences among countries in genetic merit of recent bulls have decreased markedly, especially between the US and other countries. Mean evaluation for bulls born during 1988 in the US surpassed means for bulls in France, Italy, and The Netherlands by < 3 kg for PTA for protein. Application of seven national economic indexes showed that some indexes with different mathematical forms can rank bulls similarly. If the official index for one country is assumed to be optimal, use of an index from another country could substantially reduce the mean merit of selected bulls by more than one-half an index standard deviation. Selection on either national or international genetic evaluations can give rapid genetic progress if the economic index is correct.