Estimation of genetic and phenotypic trends for calving interval in Holstein Dairy Cattle in Isfahan Province

In order to estimate genetic and phonotype trends of calving interval, records of the Isfahan Province Holstein cows that registered by Vahdat Industrial Agriculturists & Dairymen Cooperative of Isfahan from 1983 to 2010, were used. Single trait animal model was used for analysis of records. Genetic and phonotype trends were estimated using regression average breeding value and phonotype value on year of calving .Heritability for calving interval were 0.07±­0.004. Genetic trends for calving interval was -0.005±0.001 days per year. Phonotypic trends for calving interval was estimated +0.47±0.1 days per year.