Raising gilts and sows: Part 2

This week, we look at mating your pigs. Oestrus normally lasts 21 days and occurs regularly until the sow or gilt becomes pregnant. Gilts tend to have a shorter cycle of 18 to 20 days

Oestrus comes from a Greek word meaning ‘mad desire’. As biologyonline.com points out, oestrus is a phase in the sexual cycle of female animals. It is characterised by sexual receptiveness in females. Other cues include a bloody vaginal discharge.

When the ovarian follicles mature, oestrogen is secreted. Females are said to be in heat during this phase. Anoestrus is that period when the sexual cycle rests.

Simply put, oestrus makes reproduction possible. If the breeding herd does not reproduce well, fewer pigs will be available to send to market.

When oestrus approaches, there is increased activity, and also swelling and reddening of the vulva. But the gilt may not stand for the boar at this stage, warn Graeme Taylor and Greg Roese, livestock officers at The Pig Site (thepigsite.com).

After 12 to 24 hours, the vulva will diminish in size, the mucus will become the consistency of light oil, and the gilt will respond to the back pressure test.

Apply pressure to the back and flanks of the pig. Receptive females will stand rigid and their ears will often prick up.

“Only 50% of gilts will show the standing reflex or back pressure response in the absence of the boar,” say Taylor and Roese.

For this reason, direct contact with the boar is recommended for gilts. Doing so increases the proportion of gilts coming into oestrus in the first three weeks of boar exposure.

“The actual duration of the heat cycle is shorter in a gilt and therefore her period of receptiveness is shorter. Staff should be alerted to this fact,” say Taylor and Roese.