Oestrus Behaviour - Anatomy & Physiology

Introduction

Oestrous detection is a problem because mares not in oestrus can cause significant damage to a stallion.
May be a slight oedema of the vulva and a mucoid discharge.
Generally mares return to oestrous about 6-10 days after foaling.
- Called a 'foal heat' because often the foal develops diarrhoea at this time, which makes the oestrus easy to detect.
  - Fertility may not be high at 'foal heat' oestrus.
Mares with an older foal at foot may not show signs of oestrus, as they are protective of the foal ('foal shy').

Long period of proestrus where the bitch is attractive, but will not allow mating.
- Characterized by:
  - Vulval swelling
  - Presence of serosanguinous discharge

Followed by standing oestrus:
- Standing to be mated
- Deviation of the tail
- Discharge becomes paler in colour
- Reduction in vulval oedema

Clinical Methods and Assessments for Oestrus Detection

Assessment of vulval softening
Assessment of vaginal epithelial cells
Examination of the appearance of the vaginal wall.
Measurement of plasma progesterone concentration (detecting a rise in progesterone that preceeds ovulation in this species).

Oestrus detection is important, for although the queen is an induced ovulator (thus ovulation will not be missed, the LH response to mating decreases with each day of oestrus and follicles ultimately regress.
Proestrus is short and often unnoticed.
Oestrus is characterized by increased vocalization,rubbing and rolling.
Queen is more active and will seek the tom.
Stands to be mated by lowering her front quarters and extending her hind legs.
Demonstrates lordosis
Tail erect and held to one side.
Slight mucoid vulval discharge.