Estimation of genotype-by-environment interaction for milk traits based on foreign sires used in Colombia

Background: genotype-by-environment interactions play an important role in genetic improvement programs because they can change the performance of a breeding individual according to the environment where it is evaluated. Objective: to determine the genotype-by-environment interactions for some important traits in dairy farming among countries supplying bovine genetics and assessments conducted in Antioquia, Colombia. Methods: the study was conducted in 135 Holstein herds located in Antioquia. Daughters of 180 sires were evaluated for milk yield and 186 for fat and protein percentages, and somatic cell score. The genotype-by-environment interaction was addressed using Spearman's and Pearson's correlation tests between estimated breeding values in Colombia and those estimated in the sire's countries of origin. Subsequently, the magnitude of the interaction was determined using the regression coefficient between estimated breeding values in Colombia and the foreign estimate for each trait. Results: correlations between estimated breeding values calculated in Colombia and abroad were low, with the highest correlation (0.11) for protein content and the smallest one -(0.06) for milk yield per lactation. The results show a change in the ranking of sires based on their estimated breeding value, depending on whether foreign or domestic breeding values were applied, which indicates a high genotype-by-environment interaction. The results show a regression coefficient between foreign and domestic estimated breeding values of -0.286 L/lactation, with 0.23%, 0.002%, and -0.003 scores for protein percentage, fat, and somatic cell score, respectively. All regression coefficients except that for milk yield were statistically significant (p<0.05). Conclusion: this study demonstrates a high genotype-by-environment interaction between sires evaluated in Antioquia and abroad, underscoring the need to strengthen the estimation of breeding values adjusted to Antioquia's environment.