Correlation of international sire evaluations and transmitting abilities based on interaction effects between two countries

Genotype-environment interaction arises when the ranking of genotypes chang es under different environments. An alternative model was proposed to estim ate the transmitting ability as a sum of a constant part common to two coun tries and a variable part (interaction effect) specific to each country. Se paration of the constant part and the variable part in the alternative mode l is logical because the genes controlling a quantitative trait are unlikel y to be all involved in genotype-environment interaction. The correlations between multiple-trait evaluations-across countries and the transmitting ab ilities of the proposed alternative model were compared using a combination of four factors: 1) the size of interaction variance, 2) the number of dau ghters per sire, 3) the correlation of interaction effect between two count ries, and 4) the availability of a sire's national evaluation in both count ries. The results indicated that the correlation between the transmitting a bilities of the alternative model and multiple-trait evaluations across cou ntries was higher when sires had national evaluations in both countries rat her than in either or neither country. The correlation between genetic eval uations of the two procedures dropped consistently when the number of daugh ters per sire changed from 100 to 30. The correlation between the two proce dures in one country increased with increasing numbers of daughters in the other country. As the interaction variance increased, the correlation betwe en the two procedures decreased, suggesting that it was important to take i nto account the genotype-environment interaction in global evaluations. Par tition of sire effects into the constant and interaction parts permitted th e combination of these two parts with different weights for international s ire selection.