Evaluation of antibiotic usage during late gestation on pelvic organ prolapse incidence in sows.

Throughout the last decade, rising sow mortality rates have afflicted U.S. pork producers, as mortality rates have increased from an average of 9.0% in 2014 to 12.5% in 2024. Part of this increase is due to increased incidence of pelvic organ prolapse (POP), which accounted for 22.6% of sow mortality in 2023. Despite widespread acknowledgement of this issue, mitigation strategies are lacking. Antibiotics represent a potential strategy to reduce POP incidence, as a 2019 survey reported POP incidence was lower when feed contained antibiotics compared to periods without antibiotics. Therefore, this study examined the effect of bacitracin methylene disalicylate (BMD) supplementation on POP incidence in late-gestation sows across two commercial farms. Administration of BMD differed between farms, with farm A administering BMD through the water and farm B administering BMD through the feed. A total of 1,014 sows were on trial at farm A, with 522 in the control group and 492 in the BMD group. A total of 1,275 sows were on trial at farm B, with 709 in the control group and 566 in the BMD group. Sows were administered BMD for approximately two weeks prior to farrowing and perineal score (PS) evaluations were conducted to determine presumed POP risk. In brief, a PS of 1 (PS1) presumes low risk of POP while a PS of 3 (PS3) presumes high risk of POP determined by protrusion and swelling of the perineal region. Analysis of PS between treatments revealed that BMD administration did not affect PS at either farm (