eating mud is that a nutrition deficiency?

Certainly a physical exam and lab work is in order but this generally is not a nutritional problem. This is a form of obsessive compulsive disorder. Restriction of the activity is required only if the amount of mud eaten is leading to digestive problems. Problems may include vomiting or constipation. A blockage could occur if there are rocks in the mud. There is the possibility that your dog is bored or emotionally upset for some reason. An animal communicator may be able to pinpoint the exact cause. Separation anxiety can be treated medically with Clomicalm. If this is an only pet, getting another dog to keep it company while you are away may be the answer.