Continuous administration of low-dose GnRH in mares I. Control of persistent anovulation during the ovulatory season.

The research article presents three experiments examining the effects of a continuous, low-dose GnRH infusion in mares, establishing its non-disruptive influence on normal estrous cycles while enabling ovulation and follicle development in persistently anovulatory mares. Furthermore, the study reveals the comparative advantages of GnRH treatment in accelerating the conception process.

Experiment 1: Effects on Normal Estrous Cycles

• This experiment aimed to establish whether low-dose GnRH infusion (5 microg/h) would disrupt established estrous cycles in mares.
• Results showed that treatment increased serum P4 during the luteal phase without modifying interovulatory intervals, implying it does not disrupt regular cycles. It also tended to increase serum LH levels.

Experiment 2: Influence on Anovulatory Mares

• The second experiment evaluated low-dose GnRH treatment’s effect on persistently anovulatory mares.
• The treatment significantly improved serum LH compared to controls, with all GnRH-treated mares ovulating, demonstrating its effectiveness in inducing ovulation.

Experiment 3: Role in Reproductive Recovery

• This experiment involved mares undergoing Delayed Recrudescence or Lactational Anovulation. They were assigned to two groups: GnRH/GnRH, which received GnRH treatments during Period I (2.5 microg/h for 14 days) and II/III (5 microg/h); and Control/GnRH, which didn’t get treated during Period I.
• During Period I, the percentage of GnRH-treated mares that ovulated or conceived was higher than the controls, highlighting its effectiveness in enhancing reproduction.
• During subsequent timeframes, ovulation frequency, pregnancy rate, and cycles/conception turned out to be similar between groups. However, the interval to conception in the GnRH/GnRH group was shorter than the Control/GnRH group by over ten days, suggesting that the treatment accelerates the conception process.