I just started leasing my horse over the summer so I've only had him for about 8 months. At home, we have rubber mats on our stalls so naturally, I had no idea about his hole-digging problem. However, at our first away-from-home competition they did not have rubber mats in the stalls and the ground was quite hard with packed red clay. For our turnout the next morning, I got him out of the stall and he had a huge red clay stain on his nose that absolutely would NOT come off. Any ways to keep a horse from digging holes? Thanks!!!