Spontaneous multiple ovulation and development of multiple embryonic vesicles in a mare.

The research paper discusses a case of a Warmblood mare that experienced multiple ovulations spontaneously. The development and decline of embryonic vesicles were monitored, as was the progesterone level in the mare’s plasma. Yet, the oocytes’ development capacity appeared to be compromised.

Multiple Spontaneous Ovulations in the Mare

• The researchers noted an unusual instance of a Warmblood mare that ovulated 12 follicles without any external stimulus within a span of 2 days. In regular mare physiology, multiple ovulations within such a short timeframe are extraordinary.
• All the follicles observed in this case did not exceed 22mm in diameter, well within typical follicular dimensions for ovulating mares.

Development and Decline of Embryonic Vesicles

• The team used ultrasonography to monitor the mare’s reproductive system. Six embryonic vesicles were identified on Days 13 and 17 post-ovulation.
• However, by the 26th day, a significant decline in the number of vesicles was observed, with only one surviving.
• The survival and development of this remaining conceptus were subsequently tracked until Day 42. The specific reasons for the disappearance of the other five vesicles are not addressed in the abstract. However, a decline in the number of vesicles could be indicative of early-stage resorption or failure in the embryos’ development.

Progesterone Levels in Plasma:

• The study assessed the changes in progesterone concentrations in the mare’s plasma, an essential hormone for maintaining pregnancy in mares. A rise in progesterone was noticed on Day 7, reaching 14 ng/ml.
• Over the next 8 days, the progesterone levels saw a decline and later plateaued to approximately 4-6ng/ml until Day 70, indicating the hormone’s role in this occurrence of multiple ovulations and subsequent embryonic developments.

Impaired Developmental Competence of Ovulated Oocytes:

• The multiple spontaneous ovulations were a recurring event in this mare. However, the team found that the developmental competence of the ovulated oocytes seemed to be impaired.
• The impairment could perhaps be contributing to the reduced number of viable embryonic vesicles, although further investigation would be needed to establish a causal relationship.