Influence of calving season on the interactions among reproductive disorders of dairy cows

The objective of this study was to evaluate the influence of calving season on the interactions among reproductive disorders prior to conception and t heir effect on subsequent reproductive performance in dairy cows. Data from 3170 lactations of Holstein-Friesian cows that subsequently conceived were analysed by means of path analysis techniques. The cows were from nine com mercial dairy herds in north-eastern Spain. Lactation incidence rates for r etained placenta, metritis, ovarian cysts and repeat breeding (more than fo ur artificial inseminations per conception) were 6.4, 3.7, 5.4 and 7.9%, re spectively, and there were no differences between warm (May to September) a nd cool (October to April) calving seasons. However, our data show that cal ving season influenced the interrelationships among reproductive traits. La ctation number was not related to any of the path model variables for cows calving in cool seasons and retained placenta did not directly influence ov arian cysts or repent breeding. In contrast, older cows that calved during warm seasons showed an increased risk of experiencing retained placenta, ov arian cysts and more days open; retained placenta was a direct risk factor for ovarian cysts and repeat breeding. Our data indicated that a cool seaso n decreased interactions among reproductive disorders of dairy cows. Cows t hat calved in a cool environment could more effectively cope with reproduct ive disorders prior to conception and this fact was mainly observed in olde r cows.