Dogs eating Poop and Grass

My oldest Dane (pretzel)is 10 in April He eats poop. Is he missing something in his food? We have 3 Danes and they all have their noses to the ground and they graze on grass. We do have moles from time to time. Are the Danes missing something in their food. We do kibbles and bits food. we do the weight one for sugar (5YR) and and the balance on and chicken one half and half for Big Foot (3YR)and pretzel. Pretzel and sugar are the parents of foot. Parents have been fixed.

 

Answer from Dr. Gaylord Brown:
There is a commercial product called forbid that, when fed, breaks the habit. Episodic reinforcement is often required to keep them from going back to this bad habit. Eating poop or grass is not an indication of a nutritional deficiency.