Unfortunately, despite appearences, bull breeds tend to have very sensitive tums. I would look at the diet you are feeding. Make sure it is premium, wet if possible or wet the dry food. Bullies should have at least 2 meals a day, preferable 3. Another option is to spread the food over a floor, so he has to 'graze' the food (combats boredom also) if you are not feeding premium dry, the food can massively swell in his stomach, making him throw up and worst case scenario, causing blat.