If you give your dog more than the daily recommended serving of bully sticks, this may upset his stomach. Because bully sticks are so high in protein, feeding him too many can cause your dog to begin vomiting or experiencing diarrhea from an upset stomach. Immediately introducing bully sticks into your dog’s diet can also upset his stomach. To prevent this, give him a short time frame for chewing. As your dog becomes more accustomed to them, you can increase his chewing time.