Potential signals mediating the maintenance of reproductive activity during the non-breeding season of the mare.

This research investigates the continuation of reproductive activity in certain mares during the non-breeding season, despite this going against the typical seasonal nature of mare reproduction. With a special focus on the potential influence of body fat and energy availability on these outlying reproductive patterns, the research provides new hypotheses on the regulation of mare reproductive rhythms for future studies.

Research Context

• The study is set within the context of understanding the reproductive activity of mares, specifically how some continue breeding even during the non-breeding season.
• Previous research has mainly focused on mechanisms behind the initiation of the breeding season in mares and much less information is known about the termination of the breeding season.
• The investigated phenomenon of continued reproductive activity during winter most commonly occurs in mares who consistently maintain a non-pregnant state over successive years.

The Role of Adiposity in Reproductive Activity

• Maintaining non-pregnancy could lead to an increase in the mare’s total body fat percentage, which forms the researchers’ hypothesis that the degree of adiposity (or fatness) may influence reproductive activity during non-breeding season.
• To examine this, the researchers manipulated the mares’ fat stores through pharmacological treatments or feed restriction.
• Despite the changes made, the study found that manipulation of body fat during autumn did not change the mechanisms causing anoestrus (a period of sexual inactivity) or affect the number mares exhibiting oestrous cyclicity (recurring physiological changes associated with ovulation) throughout winter.

New Hypotheses for Future Research

• The researchers have proposed two new hypotheses for further study after their fat manipulation experiments proved inconclusive.
• The first supposes that anoestrus, as part of the long-term regulation of seasonal reproductive rhythms in mares, might be related to the recognition of available metabolic fuels before perceiving a change in the daylight length.
• An alternative hypothesis suggests that termination of the breeding season might only occur when a certain level of energy availability is reached, enough to initiate a presumptive inhibitory daylight signal. This might work in conjunction with an increase in body fat.
• The aforementioned proposals have been derived from both previous and current research.