How much food to give a adult German Shepherd?

It depends on the individual dog. I have two females of similar size. One eats eight cups per day and the other three cups per day. One simply has a higher metabolism than the other. Start by feeding the amount recommended on the bag of dog food. If you can see your dog's ribs, you aren't feeding enough. If you can't see his waist, you are feeding too much. German Shepherds should be lean, fit dogs. So don't forget to give them lots of exercise too. Your vet can also advise you on whether your dog is the correct weight at your annual vet exam.