I am interested in how breeders of the Manx cat are able to create healthy cats. We know that the gene that causes taillessness in the Manx is a nasty gene, which potentially causes severe health problems in living Manx cats and which causes the death of embryos before birth.
Kittens die before birth when they are homozygous for the Manx gene. “Homozygous” means possessing a pair of identical alleles at a place (locus) on the chromosome. The Manx gene is symbolised by the capital letter “M” because It is dominant. The CFA say it is “incomplete dominant”.
At one time breeders were not aware that kittens were dying in the womb. I presume there was no evidence of their existence except that there was a decrease in the average number of young per litter when Manx mated Manx cat, which is when the offspring will be homozygous to the M gene.
Some kittens are stillborn and some cats die before 12 months of age. In cats that survive, the effect of the Manx gene is not only seen in a short tail or no tail. There are defects along the entire length of the cat’s spine.
At the front of the vertebral column the vertebrae are shortened, while in the rear part there are missing vertebrae and fusing of vertebrae. There are umpteen deficiencies, potential or actual, to contend with such as spina bifida and the spinal cord terminating prematurely, which means nerves do not reach certain internal organs or the hind limbs (‘Manx syndrome’ describes the various problems).
Surely, it must be a breeder’s nightmare. Of course, breeders cannot mate Manx with Manx because that results in kittens dying inside the womb. But do breeders do this?
It would seem certain that breeders should have to mate Manx with a random bred cat or a cat of another breed to at least minimise the number of kittens born with health problems.
However, the Cat Fanciers’ Association says that outcrossing is not permitted. “Outcrossing” means introducing a different breed or random bred cat into the breeding line. They also say:
…Once a Manx kitten gets past the age of six months the majority of well-cared-for pets live long lives – 15 or more years…
This implies that kittens sometimes don’t get beyond the age of 6 months due to the health defects of the M gene. The CFA do not, as far as I can tell, provide information about best breeding practice on their website. They barely touch on the health issues.
Without information as to how Manx breeders create healthy cats, I must presume that they create lots of unhealthy cats and that these cats are killed by breeders at an early stage of their lives.
If I have that wrong, please correct me. It seems to me that the health problems associated with a lack of a tail are too severe to manage in a way that prevents the creation of ill kittens.
There is another hidden problem. Not all Manx cats are tailless. And some don’t have the right sort of taillessness. What happens to these cats? Who wants a Manx with a tail? Customers certainly don’t. A breeder might retain one of these tailed Manx cats for breeding purposes but how often does that happen?
My regrettable conclusion is that the Manx is a famous cat breed that is almost impossible to breed in an ethical way. It should, therefore, not be bred.