estimate of inbreeding coefficient and its effects on reproductive traits of dairy herds in isfahan province

this study was carried out to study the inbreeding coefficient and its effect on reproductive performance of dairy cows (age at first calving, calving interval and open days) in isfahan province. records of 31,977 (primiparous cows), 36,982 and 51,423 (multiparous cows) for age at first calving, calving interval and open days were used, respectively. the inbreeding coefficients of animals were calculated using pedigree information of 78,425 females and 8,056 males, which were born from 1963 to 2009. the overall mean and maximum inbreeding coefficients in holstein cows were 2.33% and 31.30%, respectively. the results showed that 57,234 animals were inbred with 3.57% inbreeding coefficient. regression coefficients on inbreeding coefficient for age at first calving, calving interval and open days were 0.589±0.21, 1.08±0.15 and 0.27±12, respectively. estimated inbreeding indicated significantly negative effect on the reproductive traits in different parturition periods. the results revealed that the average inbreeding trend was increased in the dairy herds. the increased inbreeding was due to close mating systems between the candidates, and it showed negative effects on the reproductive traits in isfahan dairy herds.