Studies in mares have examined serum inhibin concentrations using immuno-assays unable to distinguish dimeric inhibin-A from inhibin-B isoforms. Inhibin-A and inhibin-B immuno-assays were used to investigate concentrations in cyclic mares, young and old (6 vs 19 years old, respectively) mares following hemi-ovariectomy, mares during pregnancy and in mares with confirmed granulosa cell tumors (GCTs). Mares with inter-ovulatory intervals of 26 days had ovulatory peaks of inhibin-A averaging 80 pg/mL with a mid-cycle nadir of 5 pg/mL. Inhibin-A and inhibin-B concentrations were highly correlated (r = + 0.79, P < 0.01) though peak and nadir concentrations of inhibin-B were not significantly different. However, the ratio of inhibin-A to inhibin-B (A/B) changed significantly through the cycle, highest at ovulation and <1 (more inhibin-B than -A) at mid-cycle. Two mares with grossly extended inter-ovulatory intervals demonstrated mid-cycle inhibin-A (and inhibin-B) excursions suggestive of follicular waves. Follicle-stimulating hormone was negatively correlated with inhibin-A and -B concentrations in all 6 mares. Hemi-ovariectomy in young mares resulted in a significant decrease in inhibin-A and inhibin-B concentrations one day later (P < 0.05) but older mares did not, suggesting a possible extra-ovarian source(s) of these hormones. Both inhibin isoforms dropped to very low levels during pregnancy (P < 0.0001), inhibin-A (P < 0.0001) more rapidly than -B (P < 0.05), so that inhibin-B became the predominant measured form throughout most of gestation (P < 0.05). Mares with confirmed GCTs had elevated inhibin-B concentrations more reliably than inhibin-A but neither inhibin-A or -B was correlated with anti-Müllerian hormone concentrations. Collectively, concentrations of inhibin-A and -B were aligned with physiological events in healthy mares, though more pronounced cyclic changes were seen with inhibin-A. Inhibin-B concentrations were significantly associated with GCTs (P < 0.01), inhibin-A concentrations were not. While both inhibin-A and -B concentrations track physiological events such as cyclic follicular activity, only inhibin-B concentrations effectively signal ovarian neoplasia in mares.

In this study we examined the timeline of mitotic events of invitro-produced equine embryos that progressed to blastocyst stage using non-invasive time-lapse microscopy (TLM). Intracytoplasmic sperm injection (ICSI) embryos were cultured using a self-contained imaging incubator system (Miri®TL; Esco Technologies) that captured brightfield images at 5-min intervals that were then generated into video for retrospective analysis. For all embryos that progressed to the blastocyst stage, the initial event of extrusion of acellular debris preceded all first cleavages and occurred at mean (±s.e.m.) time of 20.0±1.1h after ICSI, whereas 19 of 24 embryos that did not reach the blastocyst stage demonstrated debris extrusion that occurred at 23.8±1.1h, on average 4h longer for this initial premitotic event (P&lt;0.05). Embryos that failed to reach the blastocyst stage demonstrated a 4-h delay compared with those that reached the blastocyst stage to reach the 2-cell stage (P&lt;0.05). All embryos that reached the blastocyst stage expressed pulsation of the blastocyst with visible expansion and contraction at approximate 10-min intervals, or five to six times per hour. Using a logit probability method, we determined that 2- and 8-cell stage embryos could reasonably predict which embryos progressed to the blastocyst stage. Together, the results indicate that TLM for equine embryo development is a dynamic tool with promise for predicting successful embryo development.

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Transvaginal aspiration of oocytes (TVA) in the equine industry has gained more relevance and become a valuable technique to produce offspring from subfertile mares. TVA is a semi-invasive procedure and requires handling the ovaries transrectally to position them closely to an ultrasound probe located in the mare’s vagina. Once the ovary lies in close apposition to the ultrasound probe, a 12G needle is inserted through the needle guide, puncturing, aspirating, and scraping each follicle to recover the oocyte. Potential complications described include rectal tears, puncturing of blood vessels, ovarian abscesses, and peritonitis. Occasionally, problems occur after uneventful procedures, such as colic, peritonitis, pain, and anorexia. However, the source of these complications is not fully known. We hypothesize that blood and peritoneal fluid parameters would differ pre- and post-TVA in mares. A few reports provide some parameters after TVA (e.g. peritoneal protein, neutrophils, nucleated cells) without reference to pre-TVA values. These studies have not identified an effect in peritoneal fluid variables due to multiple abdominocenteses. Therefore, our aim was to analyse blood and peritoneal fluid in mares pre- and post-TVA, and to identify changes in parameters of the procedure (duration, number of pokes, number of follicles) and the mares’ clinical responses. Ten healthy mares were selected to undergo the procedure. Thirty minutes before starting TVA, a blood sample was drawn for complete blood count (CBC) and blood chemistry, and abdominocentesis was performed to obtain abdominal fluid and assess the cytology. This same protocol was repeated 24 hours after TVA. Physical exams were performed pre- and post-TVA. Paired t-tests were used to identify differences between groups (pre- and post-TVA). Spearman correlations (ρ) were used to assess the relationship between variables. There was a significant increase in peritoneal lactate (5.65-fold), peritoneal total protein (2.4-fold), and total nucleated cells (46-fold) between pre- and post-samples. These parameters were not associated with operator, number of times the needle was introduced into the ovaries, or number of aspirated follicles. The remaining parameters evaluated in CBC and blood chemistry did not differ. A positive correlation between total peritoneal protein and blood albumin was found post-TVA (ρ=0.72, P=0.01) but not pre-TVA (ρ=−0.1, P=0.65), suggesting an increase in protein level due to bleeding. Clinically, 9 mares were healthy throughout the study except one that presented signs of pain (facial grimace, anorexia, hyperthermia) the day following TVA. In conclusion, we showed changes in the peritoneal fluid during uneventful TVA procedures. The information provided by this research gives further insight into changes potentially caused by a TVA in abdominal fluid parameters. Further studies are necessary to determine expected standards and the duration of the changes after TVA.