Prevalence and risk factors of repeat breeder syndrome in Isfahan Holstein cows

The aim of this study was to determine the incidence and quantify risk factors associated with repeat breeder (RB) syndrome in Isfahan Holstein dairy cows. Calving and insemination data of parities 1 to 7 on 91727 Holstein dairy cows from 62 herds collected during 1993 to 2013 were used. Cows failed to conceive after three or more regularly spaced services in the absence of detectable abnormalities regarded as RB. A multivariate logistic regression model was used to quantify risk factor associated with repeat breeding. Least squares mean number of services per conception were 2.15 ± 0.15 and 2.54 ± 0.15 for normal and RB cows, and uncorrected values were 2.73 and 3.28 for normal and RB cows, respectively. Herd, milk yield, season of calving and season of first insemination, dystocia, stillbirth, abortion and days from calving to first service were the major factors affecting RB syndrome. Average incidence of repeat breeding was 43.7% (27.8-55.2%). Dystocia and stillbirth increased the odds of being RB by 39% and 11%, respectively (P< 0.01). Risk of being RB in high producing cows increased by 79% compared to cows with low milk yield (P< 0.01). Odds of being RB increased by 28% in cows that was RB in previous parity. Fat yield and length of dry period had no significant effect on being RB. Considering at least 75 days distance between calving and first service, insemination in cool seasons, decreasing dystocia and improving reproduction management of high producing cows, could reduce RB syndrome.