Factors Associated with First Service Conception Rate in Dansk Holstein Cows Raised on a Farm in Southern Denmark

The objective of this study was to investigate the effects of different factors on the first service conception rate (CR) in Dansk Holstein cows raised on a farm in the Southern Denmark.Data including age of cows, parity, age at the first service (AFS), age at the first calving (AFC), calf's gender, previous gestation length, calving to service interval (CSI), calving season, and service season of 699 cows was collected from the herd's database.Logistic regression was used to evaluate the effects of the investigated factors on the CR.Results showed that AFS, AFC, calving interval, CSI, and CR were 410.622.2,714.550.2,394.559.7,87.623.7 days, and 40.8%, respectively.The odds of conception in parity 3 (OR=0.41,95%CI=0.26-0.64,P<0.001) was lower than that in parity 1.A CSI of 36-60 days (OR=0.28,95%CI=0.16-0.48,P<0.001) and 60-80 days (OR=0.50,95%CI=0.29-0.85,P<0.01) resulted in a lower CR than a CSI of 81-90 days.Cows calving in spring (OR=3.59,95%CI=1.76-7.33,P<0.01), summer (OR=3.24,95% CI=1.64-6.42,P<0.01), and winter (OR=3.89,95% CI=2.07-7.30,P<0.001) had a higher CR than in autumn.Cows having service in spring (OR=3.49,95% CI=2.16-5.63,P<0.001), summer (OR=3.29,95%CI=2.08-5.19,P<0.001), and autumn (OR=3.79,95%CI=2.23-6.43,P<0.001) had a higher CR than in winter.An AFC of 671-700, 701-730, and >760 days (OR=0.34-0.52,P<0.05) conferred a lower CR than that of 646-670 days.This study indicates that parity >2, AFC >670 days, CSI <60 days, calving in autumn, and service in winter are risk factors for reduced CR in the investigated Dansk Holstein cows.