Consistency of International Genetic Evaluations of Holstein Bulls

Abstract

International genetic evaluations from August 1995 and February 1996 for Holstein bulls from Canada, France, Germany, Italy, The Netherlands, and the US were evaluated for consistency across time. Mean evaluations, expressed on a US basis, were unchanged for US bulls; evaluations for bulls from France, Germany, Italy, and The Netherlands increased about 14 kg for milk and 0.4 kg for fat and protein. Mean genetic merit of US parents of bulls sampled in Canada, France, Germany, The Netherlands, and the US overestimated bull merit. Solutions for country of bull generally were not different for other countries relative to the US; however, evaluations for German and Netherlands bulls were higher than evaluations for US bulls with the same parent merit. French bulls that were full brothers to US bulls had higher evaluations for milk and protein, regardless of country of evaluation. Intercepts for conversion equations to a US basis increased by birth year and decreased for conversions from a US basis. Future international evaluations generally were predicted more accurately by prior international evaluations than by more recently converted national evaluations; however, converted evaluations with substantial increases in data could be better predictors, depending on country. The continued use of the latest international evaluations is recommended. Improvements in methodology that increase the consistency of evaluations across time and location may be possible. Alternatively, users may need to accept some uncertainty and error in international evaluations because of limitations in available data and methodology.