You should never stop giving prednisone without a vet's advice. It should be stepped down slowly, decreasing the dose over a period of time until it is completely phased out.
Prednisone is usually helpful with these dogs with inflammatory bowel issues.
Even if your pet is only on one pill a day, you still need to step it down. Your vet might want you to go to 1/2 a pill for a week and then a pill every other day until he is completely weaned.