On our farm, in their fenced in acre, our various dogs started digging ankle twisting holes, and it was also hard on the riding mower. I broke them of this very bad habit by shoveling their poop into the existing holes, and any new ones they started. They stopped the digging very soon, and I later filled in the holes with dirt. This really worked for us.
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"I haven't heard of this but it certainly is worth a try."
Dr. Melinda, DVM, PhD