Number of services and the reservice intervals in relation to suboptimal reproductive performance in female pigs on commercial farms

This study investigated the associations of the number of services, reservice intervals (RI), parity, and weaning-to-first-mating intervals (WMI) with farrowing rate and pigs born alive (PBA) on commercial farms. The selected 117 farms included 115,442 service records and 93,867 farrowing records in 54,502 female pigs (females). A service was defined as one or more mating events within a 10-day time period of estrus. The number of services was categorized into three groups: non-return to service, first reservice, and second or later reservice. The RI was divided into 8 seven-day interval groups from 11 to 66 days and a group of 67-150 days. The effects of the number of services, RI, WMI, and parity on farrowing rate and PBA were analyzed by using the mixed-effects models. The frequency distributions of non-return to service, first reservice, and second or later reservice groups were 88.6, 9.7, and 1.7%, respectively. Farrowing rate decreased by approximately 18% with each service (P <0.05). Reserviced females exhibited a different reproductive performance as compared to non-return to service females depending on parity and WMI. In the non-return to service group, sows with WMI 7-12 days had the lowest farrowing rate (P <0.05). Meanwhile, in the first and second or later reservice groups, no differences between the WMI groups were found in farrowing rate. At parity 1 and 2, the first reservice group had the most PBA (P <0.05). However, at parity 0, 3-5, and >=6, no differences between the number of service groups were found in PBA. In the WMI 0-6 and 7-12 day groups, the first reservice group had the most PBA (P <0.05). The mean of RI was 44.5±0.28 days in 13,183 reservice records. RI decreased from 47.4 to 39.2 days as parity increased from 0 to >=6 (P <0.05). The frequency distributions of the RI 18-24, 39-45, and 67-150 days were 39.3, 12.4, and 18.8%, respectively. Gilts had lower proportions of the RI 18-24 days and higher proportions of RI 67-150 days than sows at parity 3-5 (P <0.05). No differences between RI groups were found in farrowing rate and PBA. Increasing farrowing rate in non-return to service females and minimizing RI in females at low parity improved herd productivity.