Ruttishness in pigs lasts for an average of 21 days. To test a sow for ruttishness, push down on her hindquarters.
If she stands rigid (the so-called standing reflex), she is on heat. Her vulva may also be red and swollen, with a white discharge.
Receptivity reaches a peak about 30 hours after the start of ruttishness.
Sows come on heat again four to six days after weaning. The shorter the period between farrowing and weaning, the greater the possibility that the sows’ subsequent periods of heat will be irregular.
Once ruttishness begins, bring the boar to the group of sows every morning. Ruttish sows will seek out the boar. A sow should be relatively lean before pairing, but gaining weight through good nutrition. From weaning to first ruttishness, she should eat about 3kg/day.
A sow should not be serviced before it reaches 110kg and is seven to eight months old (around the third time she comes on heat after puberty).
Ideally, the sow should be serviced three times during her period on heat. She should therefore be taken to the boar three times at 12-hour intervals.
Young and adult boars
In the case of boars, the first ripe sperm and ejaculation occurs at five to six months of age.
Puberty can be brought on sooner by putting ruttish boars and sows in adjoining pens, but boars should not be used for servicing before they are eight months old. The fertility of a boar improves up to 12 months of age.
Before 12 months, it should not be used for more than four services per week and a maximum of one per day. Allow a day’s rest between services.
Adult sows can be aggressive, so young boars should initially service young sows. An adult boar should not service more than one sow per day, with no more than six services per week and with rest periods of one to two days in between.
A boar should not service more than 15 to 20 sows per season, as an overworked boar’s fertility can decrease significantly.
Source: Elsenburg infopak by TS Brand, B Aucamp, J Botha and A Kruger.