The control of oestrous behaviour in the mare

Area of Science:

• Reproductive endocrinology
• Equine behavior

Background:

• Estrus expression in mares is crucial for successful reproduction.
• Hormonal profiles, particularly steroids, are traditionally linked to estrus behavior.

Purpose of the Study:

• To quantify sexual proceptivity and rejection behaviors in cycling and postpartum mares around ovulation.
• To investigate the relationship between observed behaviors and circulating steroid hormone concentrations (progesterone, estrogens, androstenedione, testosterone).

Main Methods:

• Behavioral observations of mares (cycling, non-lactating and postpartum, lactating Pony mares) were conducted around ovulation.
• Plasma concentrations of progesterone, total estrogens, androstenedione, and testosterone (in cycling mares) were measured.
• Behavioral scores were compared with hormone levels.

Main Results:

• Rejection behavior was observed during dioestrus and periods of low progesterone.
• No consistent correlation was found between net behavioral scores and circulating estrogen or androgen concentrations in cycling mares.
• No consistent relationship was found between behavioral scores and hormone levels in postpartum mares, regardless of silent or overt estrus.

Conclusions:

• The expression of estrus signs in mares appears to be regulated independently of circulating steroid hormone concentrations.
• Further research may be needed to identify other factors influencing estrus behavior in mares.