Effects of dietary seaweed <I>Enteromorpha prolifera</I> on growth performance, physiological and biochemical characteristics of rabbitfish <I>Siganus canaliculatus</I>

Abstract

We evaluated the feasibility of using seaweed Enteromorpha prolifera as a dietary ingredient for the rabbitfish Siganus canaliculatus.We formulated five compound feeds with different levels of dried E.prolifera,but all with 32% total protein and 8% lipid.Three of the diets contained 5%,10%,or 15% dried seaweed.Two diets contained 10% or 15% dried seaweed supplemented with 0.2% non-starch polysaccharide enzymes(NSP enzymes).The control diet had no seaweed.Groups of rabbitfish juveniles were fed one of the diets for 8 weeks.We measured growth and physiological and biochemical indexes to determine the optimum dietary ratio of E.prolifera.The addition of 5% seaweed had no effect on growth relative to the control group(P 0.05),whereas growth declined significantly in fish fed diets with 10% or 15% seaweed(P 0.05).However,there was no difference in growth between fish fed diets with 10% or 15% seaweed group and 0.2% NSP enzyme and the control group(P0.05).Furthermore,there was no significant difference in survival or the whole fish moisture,protein,fat,and ash contents among the groups(P0.05).The activities of hydrogen peroxide enzyme and glutathione peroxidase increased,whereas malondialdehyde content decreased in the liver and muscle of fish fed diets containing seaweed.Our results suggest that the optimal proportion of E.prolifera in rabbitfish diet is 5%,or between10%-15% if supplemented with 0.2% NSP enzymes.The addition of seaweed in diets may also increase the antioxidant capacity.