Understanding biological factors associated with pelvic organ prolapse in late gestation sows

Abstract

Sow reproductive efficiency is critical to the sustainability of the U.S. swine herd, and throughout the last few decades the U.S. swine industry has made significant improvements in several areas of production efficiency, including reproductive performance. However, over the past decade sow mortality rates have increased, with a disproportionate increase due to pelvic organ prolapse (POP). Most commonly, POP occurs during the peripartum period, and approximately 21% of all sow deaths are attributed to POP. Unfortunately, there is no good biological understanding of the root causes for this anatomical phenomenon. A perineal scoring (PS) system was developed, based on phenotypic observations associated with POP outcomes that can be correlated with POP risk. Late gestation sows were assigned PS using this newly developed system, and sows were assigned PS1 (low), PS2 (moderate), or PS3 (high) based on POP risk. This system was then utilized to explore differences in the vaginal microbiota in relation to POP risk (Chapter 3 and Chapter 4) in addition to identification of steroid hormones, markers of immune system activation, and other potential biomarkers of POP risk in circulation (Chapter 3 and Chapter 5). Vaginal swabs and blood were collected on PS3 sows who were parity matched with PS1 sows, and at gestation week 12 on a subset of sows. Vaginal swabs were utilized for 16S rRNA gene sequencing and differences in the vaginal microbiota between PS1 and PS3 sows, and PS3 sows that subsequently did or did not experience POP. Additionally, several microbes were observed to be consistent across studies, sharing the same trends in abundance differences between PS. Serum molecular features were evaluated via GC-MS, and differences in abundancies were detected between sows at differing risk for POP. Immune cell populations, biomarkers of inflammation and steroid hormone profiles were also altered between assigned PS1 compared to PS3 sows. Collectively, these data suggest differences exist between microbial populations, biomarkers for inflammation, and serum metabolites between sows at differing risk for POP during late gestation.