The Swedish University of Agricultural Sciences has done a study into hereditary hip dysplasia in Maine Coon cats. They concluded that the size of the cat is a major contributing factor in cats developing hip dysplasia. They also said that selective breeding plays a part not just in terms of reducing the size of the cat but in breeding with an eye on individual cats who were less likely to suffer from hip dysplasia.
Maine Coon cat breeders can’t breed for smaller cats (which would help reduce the incidence of hip dysplasia in this breed) because the breed standard prevents breeders developing a cat which is too delicate in bone structure and which is not rugged in appearance. These cats should be solid and historically they have been the largest domestic cat breed.
As breeders are reluctant or can’t breed for smaller sizes they have to find some other form of selecting breeding to achieve the goal of reducing hip dysplasia. I presume that will mean selecting individual cats who are less likely to develop the condition and introducing them into breeding lines.
The research found that a cat’s hips get worse as the size of the cat increases. They recommend, in a commonsense way, that it is not a good idea to promote large body sizes in domestic cat breeding. A Swedish health programme with respect to this cat breed has proved successful in reducing the incidence of hip dysplasia. Domestic cats, as we know, are very good at hiding pain and the Winn Feline Foundation makes it clear (as does commonsense) that for some individual cats who are severely affected it is a painful condition. You can tell because these cats may look stiff when they walk and they may be reluctant to jump or climb. They sometimes appear lame.
The fact that hip dysplasia can cause chronic ongoing pain is surely a good reason to try and eliminate or reduce this inherited condition. The Swedish study stated that hip dysplasia was relatively common in Maine Coon cats at one third of them being affected. The problem needs to be dealt with. It is unethical to breed cats who will go on to feel chronic pain. In fact it is also probably a breach of cat association standards but that is an inconvenience which is quietly brushed under the carpet.