Yeah, they are very rare as a genetic mutation, but do show up occasionally in domestic herds. Farmers learned that they were less prone to hoof rot and by 1908 there was a breed designation for them. They gained in popularity as a premier pork meat until the beef industry took a huge chunk out of the market after the 1930s. At that time, there were hundreds of registered mulefoot herds around the US and Canada. Now, they are almost extinct as a domestic breed and feral mulefoots are very rare. The condition can be bred for and so is hereditary. I am guessing that my success with getting so many probably stems from there having been a domestic population in the area at some point in the recent past. Of course, this is a trait most people will miss if they aren't looking for it. I would be willing to bet that hunters kill more of these than we realize exist, but nobody is really looking at the feet.