During this time, the female seems more excited and increasingly aware of her environment. Gilts, however, have a much longer and more pronounced proestrus than sows. Also, the vulva of a gilt becomes more swollen and redder in color than it does in a sow. The physiological and behavioral aspects of estrus are caused by increased estrogen. Physiological signs include swelling of the vulva and clitoris and a mucous discharge.
Behavioral signs are increased activity, increased vocalization, mounting, and the standing reflex.
Sows typically come into estrus five to seven days postweaning. This will be more prominent in gilts and actually starts to dissipate at the end of proestrus. Evidence of a sticky, viscous secretion at the vulva. First, touch the thumb to the vulva in order to get a smear of the secretion. The stickier the mucous, the stronger the heat.