Use of the GnRH analogue, deslorelin acetate, in a slow-release implant to accelerate ovulation in oestrous mares.

The research article is about two clinical trials conducted to assess the efficacy and safety of the hormone deslorelin in accelerating ovulation in mares. The hormone was found to reduce the time to ovulation and the duration of oestrus, but its impact on pregnancy rates was mixed, with similar rates for treated and placebo mares at the second oestrus.

Background

• The study was based on the use of GnRH (Gonadotropin-releasing hormone) analogue, deslorelin, in a slow-release implant. This hormone is used in veterinary medicine, particularly in controlling reproduction in animals.
• The objective of these trials was to assess the impact of this hormone on acceleration of ovulation in mares.

Methodology

• The clinical trials were conducted in two different settings, with the first trial including 174 mares studied across six locations in Canada and the second trial including 98 mares studied across three locations in the USA.
• Deslorelin was administered subcutaneously as a short-term implant to normally cycling mares in oestrus with a dominant ovarian follicle more than 30 mm in diameter.
• Follicles were monitored every 24 hours by ultrasonography until ovulation occurred.
• The mares were then either mated naturally or inseminated artificially.

Findings

• The results showed that the use of deslorelin significantly reduced the mean time to ovulation in both trials. The treatment led to an increase in the percentage of mares ovulating within 48 hours.
• In the second trial, the duration of oestrus in the deslorelin-treated mares was reduced and the number of matings or artificial inseminations was also reduced.
• However, the impact on pregnancy rates was varied. In the first trial, pregnancy rates for matings at the treatment oestrus were not significantly different for deslorelin-treated and placebo-treated mares. In the second trial, pregnancy rates were reportedly lower for deslorelin-treated mares, although these rates equalized for both groups of mares after mating at the second oestrus.

Implications

• The study concludes that the use of deslorelin can reduce the time to ovulation and it has potential in improving breeding management in mares.
• However, the results also indicated a need for further research on the impact of deslorelin on pregnancy rates following its use to accelerate ovulation.
• Importantly, the treatments showed no systemic side effects and only slight, short-duration local reactions at the implantation sites.