Both humans and animals need a variety of enzymes, this for a proper digestion of among other fats, carbohydrates and proteins. The main one is betaine HCL. This enzyme is produced as soon as fats and carbohydrates are eaten. Betaine is in small amounts can also be found in wheat products, fish and shellfish.
A carp has no stomach, partly because he is able to determine whether it contained food is or is not worth repeating. It goes without saying that such products as Betaine longer-term better than to full advantage at an instant session of a few hours.