Breeding and pregnancy

The charity does not deal directly with breeding guinea pigs, apart from taking in unwanted, pregnant sows and their litters.  However, you may find some of the following information useful for guinea pig pregnancy.

Puberty: Sows – 4 weeks, Boars  – 6 Weeks

Ideal breeding age: 5-6 months

Gestation period: 63 – 75 days

First litter size: 1-3

Subsequent Litters: 3-6

Birth Weight: 60-90g/2-3oz


Not one of our favourite words. Before you decide to breed please bear in mind that there are an abundance of unwanted guinea pigs, and rescue centres all over the country are bursting at the seams with rescues after irresponsible breeding. However, in the interest of the welfare of guinea pigs we have decided to put together this guide to caring for a pre- and post-natal guinea pig and her babies.

If you must breed you should be responsible for the care for the off-spring or have made prior arrangements for new homes at weaning. Far too many people act irresponsibly once the euphoria of birth and weaning has worn off.

We see a substantial number of unwanted guinea pigs as a direct result of irresponsible breeding and ask you to carefully consider the consequences before breeding your guinea pigs, taking into account, extra cost, less room, more responsibility, inbreeding, and stress on the sow.

So the rules are:

  1. Never in-breed (can cause a multitude of problems including blindness, deafness, dental abnormalities and mental impairment to name a few)
  2. Never breed Dalmatians and Roans together as the offspring will more than likely be born with genetic abnormalities
  3. Never breed from a sow which is more than 12 months old as the pubic bones may not allow a flexible exit for the young, unless she has already had a litter
  4. Never breed from a sow which is more than 3 years old, or breed over and over again from the same sow
  5. Get your breeding pair healthchecked to ensure they are fit and well and that there will not be any genetic abnormalities passed on to the new litter
  6. Never deprive your pregnant sow of plentiful fruit and veg, especially greens, which are important for milk production
  7. Never ignore warning signs that all may not be well with your pregnant sow if she is listless, dribbling at the mouth or has vaginal discharge
  8. Never ignore a baby left in its unbroken amniotic sac.  You can gently break the sac open yourself, at the snout end, with a thumbnail, give a little rub and pop back under Mum
  9. Never take the nutritious afterbirths away, as the nursing mum will eat them (the only time they become carnivores)
  10. Never ignore a sow who continues to grunt and bear down to no avail. Get to the vet pronto!
  11. Never ignore a new born baby lying cold and motionless. Warm up the baby by gently rubbing it all over and jiggling it about in your hands until you instil life into it, then put under Mum
  12. Never let the babies eat greens until they are eleven days old but continue to give them to Mum (you will need to supervise)
  13. Always remove boars from the litter by 4 weeks as some reach puberty sooner

Once again, please, please, please consider very carefully before breeding from your guinea pigs.

Sexing your guinea pigs

The confusing aspect is that both sexes have a “Y” shape at the genital area.  So how do we define boys from girls?

With boars, in the centre of the upper part of the “Y” shape you should see a raised dot with a ring around it.  Although the penis will be retracted, this is a fairly obvious sign.  As he gets older you will be able to confirm his gender by gently pushing above the ring, when his penis should “pop” out.

With sows, a neater “Y” shape can be seen with no ring around the dot in the upper part of the “Y