Genotype×environment interaction in feeding systems and sire countries for Holsteins

Abstract

The objective of this study was to investigate the effects of genotype by environment interactions in feeding systems and sire countries for production traits of the first lactation cows in Hokkaido. Phenotypic values were regressed on sire predicted transmitting abilities (PTA) to measure an existence of a scaling effect between two environments. Under considering production traits in each feeding system as different traits, genetic correlations of the traits were estimated by an animal model. The feeding system was classified by grazing, confinement and unknown, and the sire country was classified by Japan, USA, Canada and others. A significant scaling effect was observed in grazing herds. Regression coefficients of PTA of sires from USA and PTA of sires from others countries were higher than 1, whereas, Japan and Canada were less than 1, excluding protein yield in Canada. Their values of Japan ranged from 0.92 to 0.95. Genetic correlations between feeding systems ranged from 0.98 to 0.99, suggesting that national genetic evaluation for Holsteins in Japan does not have to consider the difference in feeding systems.