RESUMEN
Delayed conception is defined as an interval of greater than 90 days postpartum before a cow becomes pregnant again. In this study, the risk factors for delayed conception in Korean dairy herds were determined by evaluating several reproductive factors in individual cows. The following data was recorded from 1,012 pregnancies in eight dairy herds (designated A-H) from July 2001 to June 2006: herd, cow parity, repeated animal (cows included 2, 3, or more times), calving season, calving condition (abnormal partus), postpartum disorders (retained placenta, metabolic disorders, metritis and ovarian cysts) and conception. Logistic regression was used to evaluate the effects of these factors on delayed conception. A stepwise procedure was used to obtain the appropriate model (alpha = 0.05), which revealed the herd, metritis and ovarian cysts to be significant risk factors for delayed conception. The odds ratio showed that the likelihood of delayed conception increased by 3.3 and 2.0 fold for each incidence of metritis and ovarian cysts, respectively. Delayed conception was significantly more likely in 2 herds, in herd A by 2.0 fold and in herd B by 2.4 fold, compared with herd H. These results suggest that the prevention of postpartum metritis and ovarian cysts, as well as improved herd management, will be needed to maintain a short interval between calving and conception in Korean dairy herds.