Stage-specific metabolomic changes in equine oviductal fluid: New insights into the equine fertilization environment.

This research aimed to study the chemical composition of equine oviductal fluid (OF) at different stages of the ovulation cycle to understand better its potential effects on in-vitro fertilization (IVF) and sperm function in horses. By identifying and analyzing various metabolites in the OF, the team found that the fluid’s make-up changes between pre- and post-ovulatory stages and that these changes could influence the functionality of stallion spermatozoa.

Objective and Methodology

• The researchers sought to develop a detailed profile of equine oviductal fluid (OF) at two different stages – pre-ovulatory (PRE) and immediately post-ovulatory (PST) – using proton magnetic resonance spectroscopy (H NMR). This was intended to advance understanding of the chemical environment that equine sperm confront during the fertilization process.
• Fluid was extracted from eight mares before ovulation and six mares after ovulation. Five samples were prepared from each group for study.

Findings

• Analysis identified 18 different metabolites present in the OF samples. The metabolites found in the highest concentrations were lactate, myoinositol, creatine, alanine and carnitine.
• Only two metabolites – fumarate and glycine – showed significant differences between the PRE and PST samples. Both were found in higher concentrations in the PST samples.
• The team then carried out a preliminary study, treating sperm from three stallions with different concentrations of OF from one mare. This was in order to observe if the OF had any effect on protein tyrosine phosphorylation (PY), sperm motility, or acrosomal status.
• After incubating the sperm for four hours, they noted an increase of PY in sperm from two stallions when exposed to 0.0625% and 0.125% OF solutions. However, no change was observed in the third stallion. Neither did the OF seem to have any effect on motility or acrosomal status.

Conclusions

• This research presents the first detailed study on the metabolomics of equine OF at different stages of the estrus cycle, thereby providing valuable insights into factors affecting equine IVF. Results suggest that the OF’s composition does change during ovulation and that these variations may have an influence on PY in stallion spermatoa.
• The study’s findings signal potential avenues for future research, particularly on how manipulating the chemical composition of IVF media might enhance equine IVF success rates.