Pigs cool, pork

Pork production: Do pigs become infertile in summer?

Question: My friend and I are both newcomers to pig farming. My friend heard that pigs often become infertile in summer – is this true?

Pigs don’t really become infertile in summer, but if the weather is very hot they may not breed as well as they do in cooler weather. This is called “summer infertility”.

Pigs are very sensitive to heat, because they can’t sweat. If the place where they are kept is hot, the last thing they are going to feel like is breeding!

There can also be temporary direct effects on fertility. The testicles of the boar are in an exposed position and have a good blood supply so that they can lose heat quickly. They should always be cool to the touch. If the temperature is high enough to cause the boar’s temperature to rise, this cooling mechanism may not work very well.

This is bad for the sperm, because they die at higher temperatures. The heat doesn’t affect the sow’s fertility directly, but being too hot is very stressful and if she’s in the early stages of pregnancy she may reabsorb the embryo and return to service.


There are some things you can do to make sure your pigs are as cool as possible. The pig pen should be well-ventilated to ensure good air circulation. This can be done by having the upper half of both sides of the shed open (they can be closed with heavy plastic curtains in winter).

The roof can be constructed in a way to allow for a space along the top, instead of the two halves meeting in the middle. Hot air rises, so it’s drawn out at the top and cooler air comes in from the sides. Painting the roof white or silver helps to reflect the heat.

If the pigs are kept in open housing or pens, make sure there’s enough shade for all of them. Watering an area to make a mud bath is also very helpful in keeping pigs cool and happy.

Whether they’re kept indoors or out, sprinkling water on pigs at the hottest time of the day also keeps them cool, and they enjoy it very much. Make sure the pigs have plenty of water to drink and that the water is cool – if the water pipes are exposed to the sun, cover them with a very thick layer of sacking; and if the pigs don’t have piped water, make sure the drinker is always in the shade.

As long as the pigs are kept comfortable during hot weather, they should reward you with piglets at any time of the year!

  • This article was written by Dr. Mary-Louise Penrith and first appeared in Farming SA.

share this