Lab with Nail Problems !!!!

[deadfeathers]

I have a six year old Black Lab that over the last two years has had a chronic problem with his nails cracking on his paws. It's happened probably 4 times on one of his back paws (same foot and nail), and now twice on his front paws (different feet). They crack right down the center with one side of it breaking up and having to be cut off, while the other side of the nail stays down and adhered to the undergrowth(not sure what you call it). Once they break it seems that they never grow back right and hence they keep breaking. The back nail has almost seemed to die and there is only a litte stub their. Any how my question is, is there any reason for this, a deficiency in his diet, etc....

Or is there any way to prevent it from continually happening. Its gotten to the point I don't even take him into the vet anymore. Just trim it myself, call the vet for some antibiotics so the foot don't get infected, and we go back to it... Well if any of this makes any sense, I would appreciate some advice.. Thanks.