Comparison of genetic trends for production traits of Holstein cows at difference claimants of Iran

The aims of this study were to estimate the genetic trend of production traits for Holstein dairy cows at different climates zone of Iran. For this purpose, 301649, 268035 and 151091 records of respectively milk, fat and protein yield of the first lactation were used, from cold, middle cold, temperate and hot climatic zones of the country. Genetic parameter was estimated using Average Information Restricted Maximum Likelihood (AIREML) based on univariate trait analysis. Genetic trends were computed as the regression of the animals predicted breeding values on birth years. The estimated heritabilities in the cold, middle cold, temperate and hot climates were 25±0.01, 0.27±0.01, 0.27±0.01and 0.21±0.01 for milk yield, 0.21±0.01, 0.19±0.08, 0.19±0.09 and 0.15±0.02 for fat yield and 0.21±0.02, 0.20±0.01, 0.22±0.02 and 0.29±0.07 for protein yield, respectively. The genetic trends for cold, middle cold, temperate and hot climates were 28.55±1.57, 33.21±1.95, 33.40±1.86 and 10.90±0.83 kg/year for milk yield and 0.56±0.04, 0.71±0.03, 0.62±0.06 and 0.22±0.03 kg/year for fat yield and 0.77±0.04, 0.89±0.05, 0.79±0.06 and 0.04±0.02 kg/year for protein yields, respectively. The genetic trends of all traits in hot climate was differed than those of the other climates (p<0.01).