There is no definitive answer to how many brussel sprouts a dog can eat. The amount that is safe for a dog to consume depends on the size of the dog, as well as the other factors such as overall health, age, and activity level. For example, a large dog may be able to safely eat more brussel sprouts than a small dog. In general, it is best to err on the side of caution and give your dog only a small amount of brussel sprouts at first. You can always give them more if they seem to enjoy them and are not showing any adverse effects. If you are ever in doubt, it is always best to consult with your veterinarian.