What's the difference between Canadian Sphynx, Don Sphynx and Peterbald? Besides the country of origin?
The main difference besides looks are the different genes that cause the hairlessness in the Canadian Sphynx and the Donskoy.

The Canadian Sphynx's hairlessness is caused by a recessive gene, which means that both parents need to carry that gene in order to conceive a kitten that will carry the gene as well and be hairless. in case only one parent does, it is most likely that only 50% of the litter will carry it and be hairless while the other half will have furr or they might all have furr\patches of furr. For that reason it is not recommended to breed a Canadian Sphynx with a different breed that does not carry the gene, I've seen horrible outcrosses and mutations of mixed Canadian Sphynxes (Mixing with a Devon\Cornish Rex is usually safe since all Canadian Sphynxes carry Devon Rex genes but again the hairlessness will most likely be 50\50) .

The degree of hairlessness in a Canadian Sphynx depends on how strong the gene is in that specific cat If you hear something like F1 F2 F3 F4 Sphynx that indicates the degree F1 being the weakest, mixed Sphynxes will usually carry this gene while F4 being the strongest cats carrying this gene are purebred and can be show cats as well .. out crossing different degrees will give you different results.

On the other hand the Donskoy's (Don Sphynx) hairlessness is caused by a dominant gene which means that even if only one parent carry's the gene all the baby's will most likely get it and be hairless, that makes it a lot easier to out cross successfully, which brings us to the peterbald -

The Peterbald is a cross between a Donskoy an Oriental and a Siamese.

It is said that this specific gene in Donskoy's and Peterbals's is very likely to cause health issues and although were I come from they are very popular and finding a Canadian proved to be fairly difficult, I do hear about them having digestive issues and skin problems and a couple of different issues (those two are the most common). The Canadian Sphynx can also suffer from these things but they are not caused by the gene but by different things that can appear in regular cats as well. It is still not proven but all Donskoy breeders I've met or spoke too before have told me that they can suffer from skin and digestive problems and to me it did sound like something that is related to the breed, I've never heard this from a Canadian Sphynx breeder though.
I am a Donskoy Breeder and my Canadian Sphynx has digestive problems and my Don Sphynx are very healthy. I think the unhealthiness is the crossing of 2 naked Peterbalds. The crossing of this gene result can produce unhealthy kittens.

The Canadian Sphynx's hairlessness is caused by a recessive gene, which means that both parents need to carry that gene in order to conceive a kitten that will carry the gene as well and be hairless.
If both parents carry a single copy of the gene (both parents usually have one hairless parent and one furred parent), both are furred, and there is a 50% chance each parent will pass on the hairlessness gene to any given offspring.
Approximately 25% of their offspring will be hairless.
Out of the 75% furred offspring, one third (25% out of all kittens) will not carry a single copy of the hairlessness gene, and will never have hairless offspring.
Two thirds (50% out of all kittens) will carry a single copy of the gene, and can have some hairless offspring if mated with a hairless or carrier cat.

When both parents are hairless Sphynxes, all of their offspring will be hairless. All of their offspring will be homozygous to the hairlessness gene, that is to say they will have two copies of the gene, one from both parents, because both of the hairless parents have two copies of the gene, and thus will always pass on the gene to their offspring.

in case only one parent does, it is most likely that only 50% of the litter will carry it and be hairless while the other half will have furr or they might all have furr\patches of furr.
When only one parent is a hairless Sphynx, not a single kitten will be hairless. Every single kitten will have fur. 50%, however, will carry a single copy of the hairlessness gene, and will be able to have hairless offspring following the above model. 50% will never have hairless offspring, because they do not carry a copy of the gene.

For that reason it is not recommended to breed a Canadian Sphynx with a different breed that does not carry the gene, I've seen horrible outcrosses and mutations of mixed Canadian Sphynxes.
There are several crossbreeds of Sphynx and furred cat breeds. For example the Elf Cat, which is a cross between Sphynxes and American Curl cats.
In fact, Canadian Sphynxes themselves are a crossbreed between Sphynxes and furred cats - specifically, American Shorthairs and Domestic Shorthairs. It is a part of the Sphynx breeding program that Sphynxes are allowed to be bred with these breeds, in order to keep the gene pool diverse and avoid inbreeding. Obviously 1st generation crosses will be furred (this would be the F1 Cohen spoke of). 100% of the F1 cats will be carriers to the hairlessness gene. When bred with another F1, 25% of the offspring will be furless, 50% furred carriers, and 25% furred non-carriers. When an F1 (or furred carrier regardless of generation) cat is bred with another hairless Sphynx, however, 50% of the offspring will be hairless, with the other 50% being furred carriers, once again.

Please, do your research.

(Mixing with a Devon\Cornish Rex is usually safe since all Canadian Sphynxes carry Devon Rex genes but again the hairlessness will most likely be 50\50)
Crossing Sphynxes with Cornish and Devon Rexes is generally frowned upon due to some genetic disorders associated with these crosses. Do some further research and consider if it would be ethical to breed them.

On the other hand the Donskoy's (Don Sphynx) hairlessness is caused by a dominant gene which means that even if only one parent carry's the gene all the baby's will most likely get it and be hairless, that makes it a lot easier to out cross successfully, which brings us to the peterbald -
The Donskoy hairlessness gene is indeed dominant! This means that a hairless Donskoy cat will always have a minimum of 50% hairless offspring! However, a hairless cat of the Donskoy breed (or Peterbald, for that matter) will not necessarily always have offspring that carries this gene.

Why? Because a Donskoy only requires a single copy of the hairlessness gene to display hairlessness. This means that some Donskoy will only have that single copy of the gene, and will only pass the gene on to 50% of their offspring - but a minimum 50% of their offspring will always have the hairless gene, regardless of the breed and genes of the other parent.

However, many Donskoys are homozygous (have two copies) to the gene, and 100% of these cats' offspring will be hairless.

Anything between 75% and 100% of two hairless Donskoys' offspring will be hairless to some extent, depending on the cats' genetics.

It is said that this specific gene in Donskoy's and Peterbals's is very likely to cause health issues and [...] I do hear about them having digestive issues and skin problems and a couple of different issues (those two are the most common).
I would be really interested in seeing any studies on Donskoy and Peterbalds' general health as breeds, but until such are made, I would advise you to refrain from making such general, unspecific statements. Details! Specifics! Please!

The Canadian Sphynx can also suffer from these things but they are not caused by the gene but by different things that can appear in regular cats as well.

It is still not proven but all Donskoy breeders I've met or spoke too before have told me that they can suffer from skin and digestive problems and to me it did sound like something that is related to the breed, I've never heard this from a Canadian Sphynx breeder though.
It is your opinion that Donskoy and Peterbalds' issues are related to their breed, while Sphynxes' differing needs in comparison to furred cats supposedly aren't.

Digestive and skin problems also happen in Canadian Sphynxes, as you said, but if you're going to claim none of it is related to their breed and "can appear in regular cats as well", I'm going to judge you so hard.

Canadian Sphynxes' skin problems are mostly related to their hairlessness. In a cat with hair, the sebum their skin excretes will travel off the skin along their hairs. Since Sphynxes have very little hair, the sebum stays on their skin and if the cat nor the owner washes it off, it may clog their pores. Unlike furred cats, Sphynxes sweat, and they easily get cold because of that. Sphynxes also are easily sunburnt due to the lack of hair.

Sphynxes have a higher metabolism as well, and will need more food than your run-on-the-mill furred cat in order to keep it up - they have this to help keep them warm in the absence of warm fur. I happened to see a mention online that low-grade cat food, while might not cause issues for a furred cat with a lower metabolism, may cause issues to the Sphynxes. Any cat, however, may get digestive issues from food unfit for it.

Sphynxes are also more prone to ear infections, because they do not have protective hair on the inside of their ears, and the cat's owner will be required to clean the ears regularly.

Donskoy and Peterbald cats probably have similar issues. I would be interested in knowing what further issues they may have, though.
I have had four Canadian Sphynx cats, two male, two female. The females were mother and daughter, the males
not related. I lost all four to cardiomyopathy. The expense and the heartbreak over the seven years was intense.
I now have two Peterbald males, eight months old. The are delightful, very energetic, affectionate and have
wonderful personalities. Hopefully they will remain healthy for years to come. I loved my Sphynx cats intensely
but could not put myself through loosing any more.

I breed peterbalds in australia. Supurb cats. Foundation cat is over 8 acts like a 2year old. Interested in the gene, and when suggesting problems, need to think about the ones imported through siamese.oriental mingling.

AnonymousWhen both parents are hairless Sphynxes, all of their offspring will be hairless. All of their offspring will be homozygous to the hairlessness gene, that is to say they will have two copies of the gene, one from both parents, because both of the hairless parents have two copies of the gene, and thus will always pass on the gene to their offspring.

how does this work with a canadian father and a donskoy mother? I know they are not allowed to breed but I know a person who did it. All kittens had hair when they were young, later it fell off yet remained permanently on their faces and legs. They also have whiskers. I am curious to know how did the genetics work in this case if a father has recessive gene and mother has dominant gene yet we know that donskoys come in furred version as well (wiry and velour coat). So how did a hair gene came through a dominant bald mother and recessive bald father?