How do guinea pigs breed?

Before you decide if you want to breed your guinea pigs, there are some things you need to know:

1. Female guinea pigs become capable of breeding by the age of 4-8 weeks. The males reach sexual maturity at about the same time.
2. Pregnancy is 59-72 days, with litters of 2-5 pups born on average.
3. Once your sow (female guinea pig) gives birth, it is only 2-15 hours until she is able to conceive again. That means if the male is still in the enclosure, she can be pregnant before the end of the day.
4. Guinea pig breeding is risky, at best. The females are prone to pregnancy complications – as many as 20% of all sows die while giving birth.
5. At the end of the day, you have to find good homes for the offspring, unless you want to have more pigs around, still breeding (brother-sister, mother-son, father-daughter matings are all common and ill-advised as inbreeding causes a range of problems in the offspring).

If you’re still determined to breed your guinea pigs, read on. But if you don’t want this happening, read this article.

How old should my pigs be before I breed them?

Sows should be first bred when they are large enough to bear a litter — they reach puberty as early as 5–6 weeks of age, although many breeders prefer to breed them when they achieve 350–500g (at 5–13 weeks).

During the birthing process, the pelvic bones have to separate at the pubic symphysis (where the two sides of the pelvis meet). This symphysis fuses completely at 6-9 months unless the sow is bred before then. For this reason, most breeders and vets recommend breeding for the first time between 3 and 6 months as, if the sow is bred after the pelvic symphysis fuses, there are serious and potentially fatal consequences for the sow and offspring, as she will usually not be able to give birth naturally.

Male guinea pigs will begin mounting behaviour as early as 4 weeks of age but are usually not fertile until 8–10 weeks of age. Boars are therefore first bred at 500–800 g (7–13 weeks).

Breeding cycle

Guinea pigs come into season approximately every 16 days (range of 13–21 days). The sow will accept the male for 6 – 11 hours towards the end of this cycle. She will continue to come into season every 16 days until she is pregnant. A fertile heat occurs from 2-10 hours after giving birth, at which time 60–80% of sows will become pregnant if mated.

Monogamy or polygamy?

Both monogamous and polygamous breeding occurs, with 1 boar capable of mating with up to 10 sows, depending on the size of the enclosure. Litter intervals in guinea pig colonies range from 80-96 days, and an average of 0.7–1.4 young are born per sow per month. In commercial colonies, breeders are retained for approximately 18 months, and pets may reproduce for up to 3 years.

Is she in season?

A receptive sow prowls and runs about the cage, mounts other sows, and arches her back downwards when approached by the boar. The boar will circle the sow, sniff, lick, nibble, and mount her. After one or two intromissions, mating ceases.

What to expect during pregnancy

Two-thirds or more of matings are fertile. Sows do not build nests. They may lose hair on their flanks and back and can double in size during the 59 to 72-day pregnancy. Litter size may be affected by the age of the sow (very young and old sows produce smaller litters); obesity (fertility and litter size are lower in obese sows); and nutrition (poor nutrition reduces fertility, litter size, and survivability of the pups). The length of pregnancy is shorter the more foetuses are present. Most litters usually consist of 2–5 pups.

A normal delivery occurs over a 30-minute period, with 3-7 minutes between births. The sow will readily consume the placenta after giving birth.

Caring for the young

Pups usually weigh between 45–115 g at birth although pups weighing less than 60 g (i.e., those from large litters) at the time of delivery usually have little chance of survival. The pups are precocious, that is, they are born fully furred with eyes open and teeth erupted, and within a few hours they are fully mobile. They do not nurse for the first 12-24 hours, and the sow and litter should not be disturbed during this time. Voluntary urination occurs between 1–2 weeks of age; prior to this the sow stimulates urination and defecation by licking the ano-genital region (the area around the pup’s bottom). The pups wean at 180g, or 14–28 days.

Guinea pig pups begin eating solid food and drinking water within hours of birth. They get all their maternal antibodies from the placenta, not the milk. Nevertheless, up to 50% of pups can die if pups do not receive milk from a sow during the first 3–4 days of life.

The duration of maternal care is dependent on the female’s condition rather than litter size, pup weights, or pup development. Feeding the sow a well-balanced diet during pregnancy and nursing usually leads to less deaths of both sows and pups (lower mortality). Young guinea pigs can attach to nipples on day 1, and during the first week more time is spent nursing in the light. Guinea pigs nurse sitting up; this allows the pups to push up under the abdomen to reach the mammary glands, and the sow remains immobile during the first few minutes of nursing although sound signals and other cues may prompt licking by the sow. The pups will also eat the sow’s faeces to establish the bacterial flora of their gastrointestinal tract.

The guinea pig pups begin eating solid food and drinking water a few days after birth. Food preferences are established and imprinted within a few days of birth, even if they are still feeding from the sow, and it is wise to provide a variety of foods in the first few weeks.

If the sow abandons the pups before they are a week old, or if the young are orphaned or weaned early, mortality may be high (over 50% deaths). If you have a litter of pups which has been abandoned, orphaned, or weaned early it is strongly recommended that you seek advice from a veterinarian experienced with Guinea pigs. Guinea pigs, like most rodents, will readily foster pups from different litters. If this is not possible, bottle feeding may be required. Guinea pig milk has been shown to be similar to cow’s milk, other than having a higher protein level. It has been suggested that adding egg white to cow’s milk may be a suitable hand rearing formula for orphaned or abandoned guinea pig pups.