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 their 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 commercial dairy herds in north-eastern Spain. Lactation incidence rates for retained placenta, metritis, ovarian cysts and repeat breeding (more than four artificial inseminations per conception) were 6.4, 3.7, 5.4 and 7.9%, respectively, and there were no differences between warm (May to September) and cool (October to April) calving seasons. However, our data show that calving season influenced the interrelationships among reproductive traits. Lactation number was not related to any of the path model variables for cows calving in cool seasons and retained placenta did not directly influence ovarian cysts or repent breeding. In contrast, older cows that calved during warm seasons showed an increased risk of experiencing retained placenta, ovarian cysts and more days open; retained placenta was a direct risk factor for ovarian cysts and repeat breeding. Our data indicated that a cool season decreased interactions among reproductive disorders of dairy cows. Cows that calved in a cool environment could more effectively cope with reproductive disorders prior to conception and this fact was mainly observed in older cows.