AJ Cavies

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Young Guinea Pigs are capable of breeding from 4-5 weeks, so move them away from their mothers and sisters as soon as they are weaned from the mother’s milk (this is at about 3 weeks) Guinea Pigs carry for between 65-70 days from the successful mating date. This is exceptionally long for an animal of this size, and this is a result of the animal originating in the high South American Andes mountains where the climate can be unfriendly at times. The end result is worth waiting for as when the babies are born (usually 1-6 in a litter) they are perfect little miniatures of mum and dad.

They are fully functioning, with eyes open, covered in hair and running around and capable of eating Hay, grass etc from day one.


Male guinea pigs should be about three to four months of age before being allowed to mate. However if male Guinea Pigs are not allowed to mate with a female until they are a year old, their libido will decrease, even to the extent they may become infertile, and for this reason it is advisable they are bred from as soon as they are four months of age.

With female Guinea Pigs they should have their first litter before they reach 10 months of age, because soon after this time her pelvic bones fuse and her chances of developing dystocia (abnormal or difficult labour/birth) are greatly increased.

A female Guinea Pig's oestrus (heat) cycle lasts 15 -17 days. She will only be interested in liaising with the boar for about eight hours during this time. Female guinea pigs get on quite well with their boar-beaus, so the easiest way to manage the romance is to leave the couple together until you are sure she is pregnant.

You can probably tell when the sow is in season as, during this time, she will regularly curve her spine downwards to elevate her rear end. In addition, you may find that she regularly mounts other female guinea pigs that she is living with. If you have a harem of females, a boar will be happy to cover up to four or five sows at the same time, but two males should never be put together in a large pen of females.

A sow will develop an obvious bulbous shape during pregnancy and will often double her weight. You will need to provide larger quantities of water for the ‘mother to be’ as she will often drink more than normal.

To determine when the birth of the young will occur is often difficult because they have a long gestation period and because the sows do not build nests. You may notice a slow widening of the pelvis, just in front of the external genitalia, developing in the week before birth. This separation increases to more than 2.5cms in the hours just before delivery.


An uncomplicated delivery usually takes about an hour. There is usually an average of five minutes between the grand entrance of each baby guinea pig (pup). Unfortunately, abortions and stillbirths are common with guinea pigs throughout their breeding lives.


Attention to the diet of a pregnant sow is important. It’s vital that the sow is given additional vitamin C. Like humans, guinea pigs will suffer from 'scurvy' if not given vitamin C. Guinea pigs don't have the enzyme needed to make their own Vitamin C and when pregnant, a female guinea pig will need three times as much vitamin C as she would do normally.

You can add vitamin C to the water at the rate of 200mg per litre. However, vitamin C degrades quickly in water and supplementing a pregnant guinea pig with specific foods rich in Vitamin C is advisable. Suitable foods, in the order of highest concentration of vitamin C, are dandelion greens (wash them first), kale, brussel sprouts, parsley, broccoli leaves, cauliflower, strawberries, broccoli florets, oranges or cabbage. Note that oranges and cabbage have only a quarter of the vitamin C content of dandelion greens and brussel sprouts. A cup of dandelion greens or Brussels sprouts will provide about 200 mg of vitamin C.

Pregnancies usually proceed without difficulty and the birthing process is well managed by Mother Nature. The new piggies will be running about gaily very soon after birth. It’s normal for mum to eat the afterbirth so don’t be concerned if you see her performing this revolting, but essential, task.

Guinea pig sows don’t make nests for their young but newborn guinea pigs are born quite independent. They are haired, have teeth and open eyes and can start eating solid food within a few hours of birth.


It’s important that the sow is removed to a nursery before the babies are born. Firstly, she is quite able to fall pregnant again within a few hours of the birth. Sixty to eighty percent of female guinea pigs will fall pregnant if mated at this time, but it’s too close to the production of the young for her to bear additional young safely.

Secondly, the other guinea pigs could trample the newborn and injure them and, thirdly, the sow is more likely to stay with her young and nurture them if she is not worried by other guinea pigs.


The babies should be weaned from the sow at 14 to 28 days when they should weigh from 150 to 200 grams.

They can be hand reared easily if necessary as they eat solid food in the few days following birth. However, normally a young guinea pig will suckle milk from its mother for around three to four weeks.

Separate your new guinea pigs from the mother at weaning time as it won’t take them long to learn about the birds and the bees. They will have no hesitation mating with their mother or with other guinea pigs in their enclosure.

Breeding Guinea Pigs is great fun, and looking at the range of colours and coat patterns produced is exciting. Be sure, though, that you are not breeding without having due regard to the future of the young guinea pigs. Are you able to find them good homes?

This can be done at any age but if you are trying to sex new born babies it can be a tricky matter for the untrained eye if they are less than one week old.

To carry out this procedure the Guinea Pig is turned onto its back and its weight should be supported with the palm of one hand so that the genitalia can be examined. In both sexes the anus is closely situated to the genitalia.

Females (sows): The sows usually have a smooth swelling over their genital area. Sometimes, it can be bumpy looking, making you think it might be a male! If you gently part the genital opening, on a sow, a "Y" shaped opening should appear.

Males (boars): Press gently just above the genital area. If it's a male, you should be able to make the penis slowly extrude. Don't be fooled by appearances. Sometimes, it doesn't look like there is a penis there at all! Especially in heavy, older males, the penis can be "tucked away" in folds of skin, looking entirely like a female! You should TRY to get the penis to ease out. The penis should have two prongs of even length at the end, if these are absent or of unequal length the boar is likely to be sterile.


  • Sexual maturity (female): 4 - 6 weeks
  • Sexual maturity (male): 3 - 5 weeks
  • Female breeding age: 4 - 5 months, weight 500g
  • Male breeding age: 3 - 5 months, weight 550g
  • Oestrus cycle: 15 - 17 days
  • Gestation range: 59 - 72 days (depending upon litter size)
  • Litter size: 1 - 6 (average 3)
  • Birth weight: 75g - 100g (depending on litter size)
  • Breeding life of female: 4 - 5 years
  • Breeding life of male: 5+ years
  • Weaning age: 3 weeks

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