Relationship between embryo recovery rate and uterine lavage fluid composition in postpartum mares.

The research aimed to figure out if the components of uterine lavage fluid in postpartum mares could predict conception. The study found that persistent inflammation may be the main reason for low pregnancy rates during the first postpartum estrus cycle. Further study was suggested to confirm if lysozyme or possibly TIC could be useful in predicting conception at foal heat.

Research Design

• The researchers’ goal was to ascertain whether certain elements in a postpartum mare’s uterine lavage fluid could be used as a predictor for conception. The components under investigation were neutrophil numbers (PMN), trypsin-inhibitor capacity (TIC), lysozyme, N-acetyl-beta-D-glucosaminidase (NAGase), beta-glucuronidase (B-Gase), total protein, and plasmin.
• Fifteen mares were inseminated within 13 hours after the first postpartum ovulation. Uterine lavage fluids were successfully collected from nine out of twelve mares before insemination and from all mares before embryo recovery 7 to 8 days after insemination.

Findings

• The researchers were able to recover embryos from 53% (8 out of 15) of the mares. In the period leading up to insemination, 3 out of 4 mares that did not produce embryos showed elevated levels of PMN, TIC, and lysozyme. In contrast, only 1 out of 5 mares that did produce embryos showed elevated levels of PMN and TIC, while none had elevated levels of lysozyme.
• None of the tested parameters differed significantly in mares with or without embryos. However, lysozyme was the most likely to be significant (had a p-value of 0.07).
• In both groups of mares, levels of NAGase and B-Gase were significantly higher during dioestrus (the period between estrus cycles) than immediately after ovulation. The NAGase level was found to be higher in mares that did not produce embryos at the time of embryo recovery.

Conclusion

• The results of this study suggest that a prolonged state of inflammation is the most probable reason for low pregnancy rates during the first postpartum estrus cycle in mares.
• The researchers recommended further study to confirm if either lysozyme or TIC could be useful in the prediction of conception at foal heat.