The objective of this study was to identify the effect of abortion on performance of Iranian Holstein cows that calved between 2005–2014. Abortion records were categorized in two groups: 1) new abortion (NLA), and 2) rebreeding abortion (RA). Production data (305-d milk, fat, and protein yields) were analyzed using PROC MIXED, number of inseminations per lactation period (INS), postpartum health disorders (PPHD), and culling records using PROC GLIMMIX, and calving to conception records using PROC PHREG of SAS software (SAS Institute, 2013). For each separate model, main herd-cow factors and all two-way significant interactions were considered in the analyses with results being reported for each calving status by lactation period. In total, 12.5 % of lactation periods were associated with at least one case of abortion, while 1.9 % of the lactation periods commenced with an abortion. Based on results from the present study, milk production decreased for cows having abortion classified as NLA or RA. Overall, when there was a RA, there was an increase in median days non-pregnant (DNP) by 132 d and INS by 1.6, whereas cows with NLA had median DNP of 15 d less and an INS of 0.17 less than cows with normal parturitions. Compared with cows with normal parturitions, cows with a NLA were 1.24, 1.88, and 2.41 times more likely to have PPHD, and be culled from the herd for involuntary reasons and reasons related to reproduction, respectively. The results of this study indicate abortions were associated with cow health and milk production and reproductive performance, indicating losses due to abortion are not only a direct result of the loss of a pregnancy.
