Oestrus Behaviour - Anatomy & Physiology

Sow

• Oestrus detection is a crucial assessment to ensure sows are presented to the boar at the correct time.
• Good relationship between weaning and return of oestrus, unlike the cow.
• Vulva swollen and congested 3 days prior to Oestrus.
• Desire to seek the boar.

• Observe twice daily remote from feeding time.
• Stands for a boar producing lots of pheramones in saliva.
• Stands very firmly to be mounted, hence the 'back pressure test' is very reliable.
  • But, becomes refractory after 10 minutes standing, then no visible response for 1-2 hours.

Mare

• 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').

• Commonly teasing is performed (usually daily) using a less valuable stallion over a 'teasing board'.
• Mare will stand as if to urinate, lift her tail and lean her hidquarters toward the stallion.
• Mare repeatedly exposes her clitoris ('winking')
• If the mare is in oestrus, the stallion usually demonstrates a Flehmen response.

Clinical Methods and Assessments for Oestrus Detection

• Detection of a follicle and absence of a corpus luteum by palpation or ultrasound examination of ovaries.
• Demonstration of follicle size, follicle wall thickening and follicle wall softening on ultrasound.

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Bitch

• 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

• Poor relationship between time of ovulation and external appearance.

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).

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Queen

• 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.