Breeding guinea pigs is a rewarding pastime. They are easy to mate, easy to rear and you’ll be as happy as a pig in mud watching the new squeakers growing and developing. Just be sure you can find good homes for the resultant babies.
As with real pigs, female guinea pigs are called sows and males are called boars. Sows can breed at the tender age of five weeks but this is too young. A sow should weigh a minimum of 400gm, equivalent to about three months of age, before being mated and should preferably be a little older than this.
How to mate your guinea pig
Male guinea pigs should be about three to four months of age before being allowed to mate.
A female guinea pig's oestrus (heat) cycle lasts 16 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 happy boar can service the needs of up to ten sows.
The waiting game
The female guinea pig takes her time to produce her babies. It will take from nine to ten weeks before you are rewarded with young ones. A sow will produce from one to six young, but three to four is the average. Large litters usually have a shorter gestation period (length of pregnancy).
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.
Delivering the piglets
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.
Diets for pregnant guinea pigs
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 brussel 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.
Care of the newborn pups
The pups 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 cavies 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?