Transient suppression of ovulatory ovarian function in pony mares after treatment with slow-release deslorelin implants.

The research examines how treatment with slow-release deslorelin implants influences the ovulation and estrous behavior in pony mares over time.

Summary of the Study

The study hypothesized that the use of deslorelin, a GnRH analog, in implants could inhibit ovulation in mares while downregulating GnRH receptors. The researchers conducted this experiment on Shetland mares whose estrous cycles were synchronized with 2 injections of a PGF analog.

Research Design

• The mares were divided into three groups:
• Group D1 consisted of six mares who received 9.4 mg deslorelin as slow-release implants.
• Group D2 made up of five mares, received 4.7 mg deslorelin.
• Group C, the control group, included five mares who received 1.25 mg of short-acting deslorelin.
• The health of the mares’ reproductive tracts and ovaries were monitored every second day using ultrasonography.
• Observation of estrous behavior and collection of blood samples for progesterone and LH concentrations analysis were also performed.
• Tests with the GnRH-agonist buserelin were performed on days 10 and 45 after treatment.

Results of the Study

• Until day 50, spontaneous ovulations were notably less in group D1.
• Estrous behavior in groups D1 and D2 was significantly reduced compared to group C.
• The duration until the first ovulation varied among the groups.
• On day 10 after treatment, a GnRH stimulation test revealed interactions that were undetectable on day 45 after treatment.

Conclusions of the Study

The researchers concluded that the use of long-acting deslorelin implants in pony mares could transiently downregulate the pituitary GnRH receptors. This downregulation is associated with an inhibition of ovulation and a reduction in estrous behavior.