Breeding guinea pigs is not difficult but knowing when to breed them is crucial in the survival of the sow and the piglets.
When to Breed Guinea Pigs
A female guinea pig needs to be sexually mature to breed but also not too old to give birth. This allows an extremely small window of opportunity, unless you want to have a cesarian section (c-section) performed on the sow to get the babies out (I would hope this is not your wish!).
Guinea pigs are sexually mature as young as one month of age. While it is less important for the male pig to be a certain age at the time of breeding, the female needs to be less than 10 months old (at the maximum) in order to be able to give birth naturally. Typically breeding after 5 or 6 months of age is extremely risky to the sow since the pubic symphysis fuses by 10 months of age, and sometimes earlier.
Guinea Pig Gestation
A sow is pregnant for 59-72 days (about 2 months) and typically has 3 piglets (although 17 has been recorded - yikes!).
My absolute favorite thing about guinea pigs is that unlike other rodents, their babies are born precocial. This means they have teeth, fur, squeak and run around just like the adults when they are born. They nurse within the first few days to get colostrum but also eat big pig food, like hay, shortly after birth.
If bred by 5-6 months of age, you have a good chance of a normal pregnancy and birthing process. But if bred later in life, whether by choice or by accident, you will most likely need to have a c-section performed on the sow since her pubic has fused in order to retrieve the piglets.
Hypocalcemia (low calcium), toxemia (eclampsia), mastitis, and uterine prolapse are commonly seen in pregnant sows. Therefore, it is important to monitor your pig's stools, appetite, and activity and get her checked out by her vet the moment you think something may be wrong.