ABSTRACT
This study investigated the effects of the herd, cowparity, the insemination protocol and season on the incidenceof pregnancy loss (PL) in dairy herds. Furthermore, wedetermined the downstream effects of PL on reproductiveperformance and its economic impact. The overallincidence rate of PL was 6.9% in 1,001 pregnant cows andits incidence peaked (p<0.01) during the second trimesterof gestation. GLIMMIX analysis revealed that cow paritywas the important risk factor for the PL. The odds ratioshowed that the likelihood of PL in cows with parities of 1or 2 was decreased by 0.6 or 0.5 fold compared to the cowswith a parity of 3 or higher. Following PL, the mean rateof endometritis was 23.2% and endometritis was morecommon (p<0.05) when PL occurred during the thirdtrimester than during the first and second trimesters. Themean culling rate was 46.4% and this did not differ withthe period of PL. The overall mean intervals from PL tothe first service and conception were 63.4 and 101.8 days,respectively. The mean interval from PL to first servicewas longer (p<0.01) for cows with PL during the thirdtrimester than for the cows with PL during the first andsecond trimesters. The economic loss resulting from eachPL was estimated at approximately $2,333, and this waslargely due to an extended calving interval and increasedculling. These results suggest that cow parity affects theincidence of PL, which extends calving interval and causessevere economic loss of dairy herds.