My butcher calls this 'Sawdust' and it is essentially raw meat comprised of beef, pork, veal, chicken, bone and fat in a granular form. It is literally the dust from the industrial meat saws they use. This is a terrific and inexpensive way to add some more calories to your dogs diet. I simply add a tablespoon or two to my dogs meals.
The best part is you can usually get this for very little money, sometimes free!