Breeding Healthy Hairless Rats
Things to Consider
Furless—also known as sphynx—rats are one of the hardest types of rats to breed. They often have reproductive issues and depending on the line may also be riddled with other health problems. They take a little more care then their furred counterparts. Because of this one should really think long and hard about breeding. I highly suggest that you at least master breeding furred varieties before you try furless.
Furless Genetics 101
Before you even start to breed furless you should first have a basic understanding of their genetics. There are at least four genetically unique versions of furless rats out there. This means that occasionally you can breed two furless together and get 100% furred babies. If it's at all possible, you should figure out which of the four types your breeding stock will be. I will be concentrating on rex-based furless, which I am most familiar with.
The furless gene I worked with, the one linked to the rex gene, is the most common. Rex (curly fur) was originally a spontaneous mutation. It's a dominant gene, meaning that a rex bred to a straight-haired rat will produce on average 50% more rex. If you breed two very good quality rexes together you may end up with more rexes, and you also may end up with double rex (or patchwork hairless). These rats almost look like they have mange. They have patches of fur that grows in and falls back out again. Double rexes bred for a few generations will eventually produce hairless.
Because of this common ancestry, breeding furless can also result in breeding rexes without really aiming to. Of course, two furless (of the same genetic type) bred together will result in entirely furless litters. However it's generally healthier to cross furless, at least occasionally, with furry rats. Furless is a recessive gene, meaning both parents must either display the gene or carry it in order for it to be produced in a litter. A furless bred to a furry non-carrier will produce a completely furred litter, and in rex-based furless they will also produce roughly 50% "sloppy rexes." These rexes generally look very curly before weaning, and as they age their curls get less and less dramatic, sometimes disappearing all together. This entire litter will be born furless carriers as one of their parents was furless.
The best way to breed furless (because of lactation and health issues) is to breed a furry mother (carrier) to a furless male. The litter will result in up to 75% furless with the remaining being a mix of sloppy rex and standard. If you really want to add genetic diversity, you can also breed two unrelated carriers. Of course in this case the number of furless born will be lower (25-50% of the litter).
Can a rat whose parents are both furry be a carrier? Yes, a rat that has at least one furless ancestor in its pedigree will have a chance of carrying the gene. However the more distant the ancestor the less likely it is they'll be a carrier. Keep in mind that the above percentages are averages. Sometimes spontaneous litters can be born that break all the rules and come out with drastically different percentages. This is all part of the spontaneity of genetics. We can always give educated guesses, but when it comes right down to it, Nature likes to occasionally throw curve balls.
Picking Out Breeding Stock
In order to start a line of healthy babies you have to start with healthy adults. First, you want to pick out the perfect unrelated male and female. Check to make sure their eyes are clear, properly sized, uninfected, and able to open and close. Make sure their bodies are not too thin and preferably not too fat either. Make certain their lungs sound clear and they show no other signs of illness, ever. You want to try to avoid passing common furless health problems—many of which are genetic—to a new generation.
From there, pick the oldest (healthiest) male you can. It's very hard to breed for longevity through the female's line, but since males can breed until they die this means you can breed for longer-lived babies. The female should be bred ideally at six months of age. At this point she's fully-grown, she's not too old or too young, and she's mature enough to have a higher likelihood of actually taking care of her litter. Make sure she's never been sick a day in her life. If she's never been bred before make sure she's under a year of age (at which point a female's hips will start to fuse together if she's never been bred).
The easiest way to get healthy stock is to consult your local ratteries and breeders who dedicate their time and energy to creating healthy lines in the first place. If this is not possible use your utmost digression (and caution) to search out other possibilities.
Preparing for the Litter
When breeding furless rats you should probably set up an aquarium for them. A ten-gallon aquarium is best for first-time mothers for the first week or two of the babies lives, at which point they can be put into a bigger aquarium. The ten-gallon aquarium is best because it doesn't allow too much space (some furless mothers will run off and ignore their babies if they're given too much space for the first week or so of their babies' lives). Also, it's insulated and the smooth surfaces are safest for guarding against scratches and injury.
Use polar fleece, paper-based bedding, or shredded paper in addition to the usual bedding so the mother can make a nice warm nest. From there, make sure to give the mother extra fat and protein in her diet (boiled or scrambled eggs make a fantastic supplement) and just make sure she's generally comfortable.
It's always advisable if you are breeding a first-time mother to also breed at least one furry or experienced mother at the same time (or ideally a few days before). This can prove to be a lifesaver if at any time you need a foster mother due to lactation problems or abandonment. When the babies arrive, let them nurse on their mother for an hour or so and then check their bellies. Pinkies have translucent skin for the first week or so of their lives, so you should see a white band going across their bellies and sometimes up their sides if they're really full. Keep checking periodically because furless rats can dry up before they're supposed to, sometimes very prematurely (within a few days). To help the mother, make sure when the babies start nibbling on food on their own that you provide things they can eat. Scrambled eggs or bread soaked in milk can be great for them. Cooked oatmeal, yogurt, and other soft foods are also great.
Keeping an Eye on the Line
After the babies are all grown up and sent to their new homes, it is best to ask their new owners to report back to you if any of them have any health problems at any point during their lives. Also request to know their cause of death (and age) when they die. It sounds morbid, but this sort of data can be crucial to knowing early on if your lines have any problems. Generally one case of any ailment can be spontaneous, however two or more should be reason to reconsider perpetuating your lines. The more genetically diverse the line, the less likely they are to have genetic ailments. However breeders do occasionally inbreed (called line breeding) if a line proves 100% healthy and long-lived. These lines have shown to be genetically very efficient and breeding them together will eliminate the risk of adding problems into the line by outcrossing it with someone else. This all being said line-breeding is not for the light-hearted; it should be done with utmost caution.
Cautions aside, I hope you all have a wonderful time raising happy, healthy, well-adjusted babies and remember temperament is just as genetic as physical ailments so make sure everyone is sweet as can be and you'll never be disappointed.