Nutrients must be provided in appropriate amounts and in forms that are biologically usable for optimum performance by the animal. Therefore it is as important to know the bioavailability of the nutrient as the dietary requirement. A respectable amount of data is available on digestibility of gross energy and crude protein in commercial ingredients used in fish feeds. There is, however, much less information on bioavailability of vitamins, minerals and amino acids from various natural and synthetic sources. In many cases, assumed availability values for nutrients are used to formulate fish feeds which are probably far from accurate. Examination of data presently available supports this contention.
For more Details: