Journal of Dairy Science, Vol 79, Issue 9 1659-1665, Copyright
© 1996 by American Dairy Science Association
Examination of international genetic evaluations of Holstein bulls
R. L. Powell and P. M. VanRaden
Animal
Improvement Programs Laboratory, USDA, Beltsville, MD 20705-2350, USA.
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.
