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

摘要

Artificial microdiets have been prepared for nutritional studies and for replacing live feeds in seed production of fish and crustaceans. Much knowledge has been accumulated on microdiets and their dietary values for several species. Total replacement of live feeds with microdiets has been accomplished in prawns, and optimum dietary levels of several nutrients have been reported for prawns. These studies have demonstrated specific nutrient requirements of larval fishes for some phospholipids and ofcrustaceans 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 dietary levelsof nutrients in microdiets determined without measuring net feed intake may be regarded as a conclusion without universal validity. This article proposes methods for the estimation of feed intake in crustaceans and fish fed microdiets, together with abrief review of microdiets and their nutritive values for aquatic animals. First, the methods for measurement of fat-soluble nutrients, cholesterol and fatty acids, using 5#alpha#-cholestane as an inert marker, were evaluated in juvenile prawns Macrobrachium rosenbergii and Penaeus japonicus and tilapia Oreochromis niloticus. Secondly, a new method for the measurement of feed intake using double markers, 5#alpha#-cholestane and dotriacontane, was evaluated using juvenile P. japonicus and larval red seabream Pagrus major as test animals. The significance of these methods in assessing the nutrient requirements of larval aquatic animals is discussed.