estimation of genotype by environment interaction for production traits in iranian holstein cattle

in order to evaluation of genotype by environment interactions in holstein cows, iran was divided into cold, middle cold, temperate and hot climate regions. for this purpose used from 39570, 35813 and 18955 records for milk, fat and protein yields, respectively, to progeny test for 35 sires that have 50 daughters in each climate. the data were collected by the centre of breeding and improvement of livestock production from 775 herds, during 1991 to 2009 years. breeding values for milk, fat and protein yield for each animal were predicted from multiple traits with animal model (blup). average of breeding value estimated for sires in cold, middle cold, temperate and hot climate was 75.53, 377.74, 167.08 and 81.49 kg for milk yield, -0.18, 5.42, 1.85 and 1.63 kg for fat yield and 0.96, 8.05, 3.93 and 1.94 for protein yield respectively.  spearman correlation for milk yield for cold-middle cold, cold-temperate, cold-hot, middle cold-temperate, middle cold-hot and temperate-hot also was 0.63, 0.61, 0.45, 0.87, 0.54 and 0.48 respectively, for fat yield was 0.63, 0.69, 0.52, 0.91, 0.49 and 0.40 respectively, and for protein yield was 0.61, 0.62, 0.39, 0.81, 0.48 and 0.41, therefore spearman correlation estimated show that ranking of sires was difference at different climates and existent genotype by environment interaction at difference regions of iran.