Effect of holding medium, temperature and time on structural integrity of equine ovarian follicles during the non-breeding season.

The research examines the effectiveness of different solutions, temperatures, and incubation durations on maintaining the structural integrity of horse ovarian follicles during off-breeding times. The researchers concluded that equine follicles were best preserved at 4°C in phosphate-buffered saline for up to 4 hours.

Methodology and Evaluations

• Equine ovaries obtained from an abattoir were used for the study. These were divided into 19 fragments, one of which was instantly fixed in Bouin’s solution for control comparison. The other fragments were distributed and held in either PBS (Phosphate-buffered Saline) or MEM (Minimum Essential Medium) at varying temperatures and incubation times (4, 20, or 39 °C for 4, 12, or 24 hours).
• After their respective incubation periods, all fragments were fixed in Bouin’s solution for 24 hours and subsequently subjected to standard histologic analysis.

Result Analysis

• In total, 2,567 ovarian follicles were analyzed. These included 1,752 primordial, 764 primary, 34 secondary, and seven antral follicles.
• The transporting of equine ovarian fragments in both MEM and PBS solutions resulted in a notable decrease in the percentage of structurally normal follicles with increasing time and temperature, compared to the control group.

Efficiency of Solutions, Temperatures, and Duration

• When preserved at 4°C for 4 hours, the PBS solution had a higher rate (98.9%) of morphologically normal follicles, including both primordial and developing follicles, than the MEM, which had a rate of 48.7%.
• At 39°C for 12 hours, all follicles in both solutions were degenerated, revealing a direct negative impact of higher temperatures and duration on follicle integrity.

Follicular Development Stages

• Primordial follicles were less affected by preservation than primary and secondary follicles in all media, times, and temperatures tested. The only exception was at 4°C for 12 hours in PBS, in which primary and secondary follicles were less affected.
• About 43% of antral follicles remained morphologically normal when maintained in MEM at 4°C for 4 hours.

The research thus concluded that the optimum environment for the preservation of equine ovarian follicles was in PBS at 4°C, up to a duration of 4 hours.