piglet and sow health; sows; health

Pork production: When are sows in heat and how long are they pregnant?

Question: I have just started pig farming and have 5 young females, 6 months old, and a 9 month old boar. I don’t know very much about pigs and I would like to know some figures related to pig breeding. I read that females should be 8 months old and nice and big before breeding and the boar should be 10 months old. When, and how often, will the females come on heat and for how long is a sow pregnant?

  • At 6 months of age and presumably sharing the same air space (although not the same pen) as the boar, so that they can smell him, your gilts are probably already coming on heat. You’re right to wait until they are at least 8 months old to breed them.
  • Female pigs come on heat every 3 weeks.
  • The length of pregnancy for pigs is about 115 days, which is roughly 3 months, 3 weeks and 3 days.
  • The smell of the boar stimulates the females to cycle, so it is likely that all five gilts will come on heat together.
  • With only 1 boar, it would be wise not to serve more than 2 females at one time, as a boar should not work more than 2 or 3 times a week – he needs some time to build up his sperm reserves in between services.
  • Having 5 litters at once would have other disadvantages as well. Lactating sows need extra feed of good quality and also extra water.
  • Somebody needs to keep an eye on the sows while they are farrowing – they usually manage well without assistance, but help should be on hand in case it is needed.
  • The piglets will need a good-quality creep feed before and after weaning as well as warmth and lots of clean, dry bedding.
  • This means there are extra costs you will only recover later when you sell the piglets.
  • Select the 2 gilts that are the biggest and/or in the best condition (but not too fat) when they are in standing heat to be bred first.


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

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