Instructions
Observe the sow's eating habits. Sows tend to lose their appetite during the heat period.
Observe the sow's behavior. Sows tend to be restless and may be more affectionate or irritable than usual during this time.
Look at the sow's vulva. It will become more plump and pink when she comes into heat.
Place your hands on the sow's sides, near her back and apply pressure. A sow in heat will stand still, showing her willingness to take a boar.
How to Tell When a Pig Is in Heat
When a female pig, or sow, turns 5 months old, she will begin a heat cycle. Every three weeks healthy, mature pigs come into heat and are ready for breeding. Since boars are attracted to sows during this time, pig owners should identify the signs of heat so they can breed or confine their sows as desired. The heat period can last anywhere from eight to 36 hours.