Nutritional assessment of artificial microdiets for larval fish and crustaceans

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In order to enhance the development of artificial microdiet(MD), MD were prepared and assessed nutritionally by using the larval red sea bream Pagrus major and Japanese flounder Paralichthys olivaceus as test fish.First, nitrogen and lipid sources were searched and investigated in order to make a high quality MD which is stable in sea water and contains nutritionally well-balanced nutrients.As a result, MD containing soybean peptides and fish oil calcium soap(FOCS)as the major nitrogen and lipid sources and zein as a binder(abbreviated as MBD)were found to fit to the purpose of the present study.First feeding experiment (study A)were conducted using red sea bream(30 days old)and Japanese flounder(15 days old)with several MBD containing soybean peptides with different, molecular weights, soybean protein isolate, FOCS, stearoyl calcium lactate, etc.It was possible to rear both the fish without using any live food such as rotifer Brachionus plicatilis and Artemia nauplii.Soybean peptides … More with molecular weights of about 1000 Da and FOCS had a high dietary value as nitrogen and lipid sources for both the fish.In the next feeding experiment(study B), feeding experiments similar to those in study A were conducted using the first feeding(5 days old)red sea bream and Japanese flounder.Both the larval fish were successfully reared by feeding the MBD alone during the daytimes if small amounts(1/10 of the live food, control)of the rotifer were provided only in the evening to prevent the starvation during the nighttime.Finally, study C was conducted to clarify the effects of diet composition and feeding methods on the sinking speed and intake of diet and performance of the red sea bream and Japanese flounder.The sinking speed varied with diet formulation, and the diet intake by the both fish(15 days old)changed with the sinking speed of diet and feeding frequency.Also, growth and survival of the flounder(5 days old)were altered with sinking speeds of diet provided.From the results of the present study, it is recommended to assess the physico-chemical properties of diet besides nutrient contents for the development of quality MD. Less