Estimates of GxE effects for economic efficiency among daughters of Canadian and New Zealand sires in Canadian and New Zealand dairy herds

Abstract

The existence of genotype by environment interaction (GxE) was tested for economic efficiency, first lactation and mature weight among daughters of Canadian and New Zealand sires in Canadian and New Zealand herds. The economic efficiency traits were evaluated using both British Columbia fluid milk pricing and Ontario component pricing systems for Canada and the New Zealand component pricing system for that environment. The GxE was tested at the macro level (strain by environment) and at the micro level (sires within strain by environment). Among economic efficiency traits a significant macro GxE was found only for lifetime economic efficiency when using the British Columbia milk payment system for Canada. Only protein yield and percentage, among the production traits, had significant GxE at the macro level. At the micro level significant GxE were found for all economic efficiency traits for both sire strains. Significant interactions were also found for first lactation yield traits among Canadian bulls. These later results indicate that sires rank differently in the two environments tested and that breeding values estimated in one production system may not be good predictors of merit in the other. ___________________________________________________________________________________