The control of oestrous behaviour in the mare.

This research observed the sexual behaviour of mares around the time of ovulation and compared it to blood levels of certain hormones. It found that the visible signs of sex readiness (oestrus) in mares are regulated mostly independently of these hormones in the blood.

Overview of the Experiment

• The study involved monitoring both the sexual behaviour and hormone levels of non-lactating and postpartum, lactating Pony mares during their ovulation period.
• The observed behaviour included positive and negative components of sexual activity, known as ‘proceptivity’.
• The hormone levels measured in the mares’ plasma included progesterone, total oestrogens, androstenedione, and in the case of non-lactating mares, testosterone.

Key Findings

• The researchers found that rejection behaviour in mares occurred during diestrus (when sexual activity and fertility are at their lowest) as well as periods when progesterone levels in the blood were at their baseline.
• For both cyclical, non-lactating mares and mares after giving birth, they did not find a consistent relationship between the net scores of behavioural actions and circulating levels of hormones like oestrogens or androgens.
• This suggests that there is a lot of variation between individual mares in terms of sexual readiness behaviour and hormone levels during the ovulation period.
• The researchers concluded that the regulation of visible oestrus signs is mostly carried out independently of circulating steroid hormones levels in these mares.

Implications of the Research

• This research adds to our understanding of mare reproductive behaviour and the hormonal factors that may influence it.
• It challenges the idea that circulating hormone levels are the sole or primary drivers of sexual readiness behavior in mares, pointing instead to the role of other factors or mechanisms that remain to be identified.
• The findings could be useful in the fields of animal behaviour and equine reproductive management.