The effect of an extended artificial photoperiod and gonadotrophin-releasing hormone infusions in inducing fertile oestrus in anoestrous mares.

The research investigates ways to induce fertile oestrus, or heat, in non-cycling thoroughbred mares to encourage early conception. It compares two techniques, namely lengthening the period of daylight or using a combination of extended daylight and infusing gonadotrophin-releasing hormones.

Research Methodology

• The researchers took eleven mares and subjected them to conditions of 16 hours of light and 8 hours of darkness (an extended photoperiod). This extended photoperiod tries to mimic the-long days of summer, a time horses naturally breed.
• Out of these, five mares also had osmotic minipumps implanted in them that released approximately 100 nanograms of gonadotrophin-releasing hormone (GnRH) per kilogram per hour over the span of 28 days. This treatment was aimed at stimulating the production of other hormones that could trigger ovulation in these mares.

Findings

• The results showed that the five treated mares ovulated nearly a month earlier than the untreated mares. Not only did they ovulate earlier, but their ovulation was also followed by a competent luteal phase, which is crucial for a receptive uterine environment and early pregnancy.
• Furthermore, these treated mares were actually able to conceive approximately 32 days earlier than the untreated mares, which can significantly accelerate the breeding and foaling schedule on a thoroughbred farm.

Conclusion and Potential Applications

• The researchers concluded that the combination of using GnRH pumps and an extended photoperiod starting from July 1st could be a promising technique for early induction of fertile oestrus in thoroughbred mares.
• This method could be beneficial for breeders looking to improve reproductive efficiency on commercial stud farms, thereby increasing the number of foals and potentially reducing the costs associated with each breeding cycle.