All the information below is from my knowledge and experience. I have been breeding for 10 plus years and I have learned so incredibly much and I'm still learning with every litter. It takes a GREAT amount of experience to breed cavies and you won't learn everything from the internet or books. It is okay if you have different opinions since not every breeder does things the same.
When first deciding to breed hairless guinea pigs (or regular guinea pigs), you must make sure your sow is under 7 months old when first being bred. After she is about 9 months old her pelvic bones fuse together which makes delivery impossible. If your planning on breeding your sow and she is over 9 months old then 99% of the time it will result in ceasarean section and she will most likely die. Hairless Guinea Pigs do not do well with pain and it would not be a good idea to risk her being bred so late. The sow must also weigh at least 500 grams but heavier is always better and be about 3-5 months old.
Do not breed your hairless Guinea Pigs if you have no idea what your doing! Read several books before hand, and browse several sites on the internet. This will not make you an expert. It takes years of experience to fully understand what all the signs mean when a Guinea Pig is pregnant. You can contact me about any questions you might have. Someone with experience is always the best :)
A sow will come into season about every 18 days and stay in season for about 24 hours. I have seen my cavies mate before when the sow was not in season, but it just depends on their attitude of the situation. Usually the boar should be at least 4 months old before being introduced to a female. You want him to be mature and sturdy for his new duties :) My Hairless Guinea Pig Boars sometimes get beaten up by the sows when they are not in season and some even loose a little weight from running around all day chasing them around. The sow might even spray hiim with urine to tell him that she is not ready.
When a sow is in season she will let the boar mate with her several times within the 24 hour period. The boar will do his mating dance, make rumbling sounds, and skake his little bottom to impress her. After she is bred they usually become really good buddies.
The gestation period of a pregnant cavy is about 60 - 70 days with the average being at 65 days. It's a very long gestation unlike gerbils, hamsters, or rabbits. This is because cavy babies are born completely developed, eyes open, and walk around within hours after being born. Depending on the size of the litter, you might not notice the babies moving or a change in body size until about a month before the birth. If you have experience then you will probably be able to tell sooner and usually that is a result in a larger litter. Cavies become noticeably large and can hardly walk. When she is in her last 2 weeks from delivery then I recommend not picking her up unless you cleaning the cage. Make sure you hold her rear end with one hand and her front with the other. Do not squeeze her tummy at all!! Just gently lay your hands on her sides and you will be able to feel movement and little kicks.
During pregnancy your sow will require 2 times more Vitamin C and fresh greens. I give my sows an assortment of bananas, strawberries, cucumbers, roman lettuse, spinach, carrots, etc. They also receive Vitamin C and Calcium tablets.
It is sometimes very hard to tell exactly when they will give birth. My sows are video monitored their last 2 weeks of pregnancy. Thanks to the video monitor I have watched many pregnant sows show signs that were bad and show signs that were good. I have seen many births and know when theirs problems and when theirs not. Most of the time everything goes well.
As I said in the beginning, all of this is from my point of view in which I am giving you my oppinion about. From my experience, the sows sides will get very hard when they are about to give birth. You will be able to feel the back bones, and other parts of the babies bodies very clearly. You should be able to fit your finger or more between her pelvic bones. These are both signs that she is days, maybe moments from giving birth. Make sure her bedding is extra soft and comforable.
Some immediate signs that she is in labor is a hiccupping motion which is her pushing the babies out. Other signs of labor is she might roll on her tummy and turn in circles several times looking for her babies. With each contraction she will push the babies out one at a time, with about 5-10 minutes between each baby. Some will take the sow longer to get out and some will slide their way out.
If you are present at the birth then in my oppinon, help her out. I will remove the sack on the babies nose right away and use a baby booger sucker to such out their mouths and noses. If I notice the baby barely moving then I will pull its ears gently and rub its tummy and back just like mom might do. Sometimes I will leave it next to the mom to take care of after I have removed the sac from its nose. Other babies I will pick up and make sure its moving and breathing normally. When I am present at the birth, I almost never just let her do it all. I would never want to risk loosing a baby because I didn't help.
After the birth is over you can let her eat the placentas if you would like or I just let her eat one and throw the rest away. The sow will come into season right after giving birth but never let her rebreed that quickly. It is very hard on sows already to be having babies, and she will need time to rest. I might rebreed after the babies are weaned from mom but it depends on how sturdy she looks.
CARING FOR NEWBORNS
Skinny pig babies are born fully developed with no furr unlike Baldwins. They have teeth, eyes open, and run around within hours after being born. From my experience some babies might get the shavings in their eyes and then become irritated so I put a towel down for about a week. Sows only have 2 teats which means the new borns have to take turns. Usually they are pretty good about it but I still make sure each one is at the proper size each day and watch for ones that are smaller than others because this might mean something is wrong.
I will bottle feed all the babies about 2-4 times a day if it is a litter of 3 or more. This ensures their survival and keeps them going strong. I do not force them to drink the milk, they usually suck about 1 tablespoon down in a day. They can have cat replacer milk that you can buy at your local pet store. When they are about 3 days old, I will start feeding them carrot, green brean, or mixed vegetable baby food through a syringe. They should start nibbling on solid foods within a couple days after birth. I will stop the bottle feeding and syringe feeding when I see them gaining weight normally and eating solid foods. They are weaned at about 3-4 weeks.
If you have any questions or concerns, feel free to contact me