Nutritional assessment and feed intake of microparticulate diets in crustaceans and fish

Artificial microdiets have been prepared for nutritional studies and for re placing live feeds in seed production of fish and crustaceans. Much knowled ge has been accumulated on microdiets and their dietary values for several species. Total replacement of live feeds with microdiets has been accomplis hed in prawns, and optimum dietary levels of several nutrients have been re ported for prawns. These studies have demonstrated specific nutrient requir ements of larval fishes for some phospholipids and of crustaceans for both sterols and phospholipids. However, the quantitative requirements of larval aquatic animals for nutrients are still obscure, possibly because of lack: of information on feed intake. From a nutritional viewpoint, optimum dieta ry levels of nutrients in microdiets determined without measuring net feed intake may be regarded as a conclusion without universal validity. This art icle proposes methods for the estimation of feed intake in crustaceans and fish fed microdiets, together with a brief review of microdiets and their n utritive values for aquatic animals. First, the methods for measurement of fat-soluble nutrients, cholesterol and fatty acids, using 5 alpha-cholestan e as an inert marker, were evaluated in juvenile prawns Macrobrachium rosen bergii and Penaeus japonicus and tilapia Oreochromis niloticus. Secondly, a new method for the measurement of feed intake using double markers, 5 alph a-cholestane and dotriacontane, was evaluated using juvenile P. japonicus a nd larval red sea bream Pagrus major as test animals. The significance of t hese methods in assessing the nutrient requirements of larval aquatic anima ls is discussed.