DOG EATS DRYWALL

Question
LATELY MY FIVE YEAR OLD GERMAN SHEPHERD HAS STARTED GNAWING HOLES IN THE DRYWALL IN SEVERAL PLACES IN THE HOUSE. I WAS WONDERING IF IT WAS VITAMIN DEFICIENT AND IF NOT IS THERE SOMETHING I CAN APPLY TO THE DRYWALL TO RID HIM OF THE HABIT LIKE VINEGAR OR SOMETHING ELSE NOT HARMFUL THANK YOU AND I LOOK FORWARD TO YOUR ADVICE

Answer
If you are feeding a commercial dog chow and little else, he should be getting all the vitamins he needs.  There is a spray, Bitter Apple  sold at pet stores.  

Is he at home by himself all day?  He is bored.  You could have a professional dog walker give him a walk every day.  Better yet, doggy day care.