Mate, your dog will be a super athlete, if you feed it well, flesh and bone with fats and offal too, is the very best natural diet for any breed of dog. Excersize LOTS, and at 20 months I would have long entered my dogs and be working them regularly, but entering a young dog is down to personal preference, and you know your dog best. If he has good breeding behind him, dont worry about his abilities as long as you have done your part in rearing it to the highest standard. Look into BARF diets, thats the best thing anyone can change for their workers. Dogs do better on flesh, bone, fats, offal