GJ, what makes you say boxers need a low protein diet? dogs are animals with a carnivorous background, with a digestive tract that is much more adapted to digesting and utilizing protein and fat rather than carbohydrates.
roxy - yes, of course dogs are able to taste their food and have different preferences.
if your dog has seizures, it's morelikely that something is in the food that causes them to happen, rather than something missing. many dogs who suffer from seizures improve drastically when poultry (chicken, duck, turkey) and grains (gluten) are eliminated.