Comparison of Methods to Rank Bulls Across Countries

Ayrshire (5149) and Jersey (10,525) bulls born in Canada and the US between 1950 and 1985 were ranked for genetic merit for milk and fat yields. Ranking methods included two joint evaluations (US and Canadian) using lactation records from both countries, a linear model combination of evaluations from each country’s national evaluations, combined US national and converted Canadian evaluations, and combined Canadian national and converted US evaluations. Correlations of linear model combined evaluations for milk yield with joint evaluations were .96 for Ayrshires and .98 for Jerseys for US joint evaluations and .89 and .84 for Canadian joint evaluations. Correlations of combined national and converted evaluations with joint evaluations ranged from .88 to .94 for Ayrshires and from .83 to .98 for Jerseys. Variation and correlations between joint and linear model combined evaluations were consistent across birth Received January 27, 1992. Accepted April 30, 1992. ICurrent address: INTERBULL Centre, Department of Animal Breeding and Genetics, Swedish University of Agricultural Science, Box 7023, Uppsala 75007, Sweden. 2Reprint q u e s t s should be addressed to the Department of Animal and Poultry Science, University of Guelph, Guelph, ON, Canada NlG 2W1. G. BANOSI Centre lor Genetic Improvement of Livestock2 Department of Animal and Poultry Science University of Guelph Guelph, ON, Canada N1G 2W1