This is my opinion from my education with Pawpeds;

Pawpeds observations of feline polydactyly and working with other long-term breeders of Maine Coons.

What is a Polydactyl Cat

Cats usually have 5 digits on each foot and 4 on the hind feet. Polydactyl cats have more digits per paw. For show the Maine Coon must have seven toes on each paw. Each toe must touch the ground. This is a TICA standard;

Proof of the long history of the Polydactyl Maine Coon

Arnold Plotnick was the first veterinarian to scientifically record polydactyly in the cat in 1868 and Darwin discusses it in the 1850s. Polydactyl is an inherited gene and not from inbreeding. "The polydactyl trait probably arose as a spontaneous mutation, and a polydactyly kitten from two normal-toed parents may represent a new mutation event". Two breeds that claim historical reference is the Pixie Bob and the Maine Coon. The reports claim that 40% of the Maine Coon breed was polydactyl. In 1876 a MCBFA member discovered a painting with the Maine Coon polydactyl. At one point there was an attempt to breed the natural trait out. Now there is a rise in the number of breeders working with the trait to promote and protect the trait in the Maine Coon. The polydactyl breed adds to the gene pool of cats and helps with the breed.

Clinical Studies

There are three scientific studies specific to polydactylism in cats on the Pawped site. Heredity of Polydactyl Cats by Ch Danforth in 1947, The Anatomy of Polydactylism in cats with Observations on Genetic Control by Chapman and Zeiner 1961 and Danforth's Heredity of Polydactylism. The genetic Pd gene is what expresses the polydactylism.

Heredity

''For his first study Danforth looked into the heredity of polydactyly and used controlled and uncontrolled data from a male and female cat he had found living 85 miles apart. Additionally, he used data from cats belonging to friends. In total Danforth bred 234 kittens in 55 litters, averaging 4.24 per litter, undertaking poly x poly matings, poly x non-poly matings & non-poly x non-poly matings. The biggest percentage expression (28%) was that of 6, 6, 5, 5, (ie 6 toes right forefoot, 6 toes left forefoot, 5 toes right hind & 5 toes left hind) though we do not know from what combination of mating's these expressions were initiated. He sexed only 100 kittens at birth, of those 52 were male and 48 female, unfortunately, he fails to sex the remaining 134 kittens. Danforth analyzed the feet of 97 polydactyl cats and discovered 25 different expressions of polydactyly. (See Table 1.) [8] The expression varied from just one extra digit on one front foot (5, 6, 4, 4) to two on the front, and two on the right posterior to one on the left (7, 7, 6, 5) Sadly he does not correlate between number of toes and parental polydactylism, so we do not know from this study whether or not number of toes on both parents affects number of toes on the offspring. However, he does suggest that there is "little correlation between grades of expression and offspring".

Danforth concludes: "The evidence thus far accumulated indicates that in the cat polydactyly is conditioned by a single dominant gene whose probable chief effect is to incite some changes in the pre-axial part of the limb bud causing an excess of growth in that region. From this excess tissue, enlarged supernumerary digits are developed, none of which in itself has a genetic individuality. The trait is not related to sex, and no evidence is found that its gene is lethal when homozygous."

It would appear that polydactyly is a simple autosomal dominant trait with variable expression and a cat needs only one copy of the gene to express it. However Danforth found that even when breeding poly x poly only 76.23% of the offspring expressed the trait to some degree. When breeding poly x non-poly almost one third (32.5%) of the offspring were polydactyl. Danforth surmised from his results that only three of the cats used were homozygous for the trait, therefore, even when bred to a non-poly 100% of the offspring was polydactyl. The only way of knowing whether the cat is heterozygous or homozygous for the trait would be through test breeding, though the chances of homozygity would likely be increased where the offspring results from two polydactyl parents. The heterozygous cat would carry the Pd & the pd gene therefore in these cats the trait cannot be fixed and this is true even when breeding two polydactyl cats together assuming they were both heterozygous. (Plotnick [1].)'' (copied from pawped website) Tica Website

Conclusion:

Maine Coons are one of the natural breeds that have polydactyl feet. They originated in Maine, where the weather was harsh, with deep snow. The poly feet helped them navigate the deep snow. There was a large percentage of Maine Coon Polydactyl. This has helped the breed by adding more cats to the gene pool. I have a personal love for the Maine Coon Polydactyl cats. I have enjoyed showing and breeding to the The International Cat Association standard. Polydactylism is not from inbreeding and is part of the natural breed.