A comparative study on the effect of fish meal substitution with three different insect meals on growth, body composition and metabolism of European sea bass (Dicentrarchus labrax L.)

Abstract

Insects are considered a sustainable alternative protein source in aquaculture diets. So far, most studies regarding the inclusion of inset meals in the diets of farmed fish focus on one insect species individually and they are examining the effect of different insect meal inclusion levels. This is a comparative study of the use of three different insect species in the diets of European sea bass. During the twelve-week experimental period, fish (average initial weight of 5.7 g) were fed with isonitrogenous and isoenergetic diets in which 30% of the fish meal was substituted with insect larvae meals from Tenebrio molitor (TM), Hermetia illucens (HI) or Musca domestica (MD) three times a day for seven days per week. Under the experimental conditions, growth performance was similar in fish fed either insect inclusion diets or the fish meal diet. The inclusion of TM resulted in a slight increase in feed conversion ratio. The inclusion of HI or MD did not significantly affect the whole-body composition and nutrient retention; however, inferior nutrient efficiencies were observed when fish meal was replaced with TM. The fatty acid content of the diets affected greatly the whole-body fatty acid composition. Fish fed on the rich in n-3 polyunsaturated fatty acids diets (FM and HI) had the highest content of n-3 fatty acids while fish in the TM and MD groups had the highest n-6 polyunsaturated fatty acid content due to the abundance of these fatty acids in the TM and MD diets. The whole-body amino acid profile was not affected by different insect diets or FM replacement. Amino acid retention varied between groups without showing any dietary effect. Plasma cholesterol levels were lowered in fish fed the TM and MD diets. Plasma triglycerides, phospholipids and lactate were not affected by the FM substitution, but differences occurred between the insect diets. Liver amino acid catabolizing enzymes activities (ALT, AST and GDH) were similar in all fish groups. Overall, this study shows the efficacy of insect meals as a fish meal substitute and that fish meal can be successfully replaced by Tenebrio molitor, Hermetia illucens and Musca domestica meals in 30% in the diets of European sea bass.