What kind of puppy food is it? The bull terrier needs good, hard food to keep it's teeth healthy and strong. Also, in human years, how old is your dog? My dog is a small Shih Tzu and she eats big dog food now and she is Human years: 5 Dog - Years: 35 . She's been eating that since age 2 or 3. I think your dog will be ready before then.