Tenebrio molitor meal in rainbow trout (Oncorhynchus mykiss) diets: effects on animal performance, nutrient digestibility and chemical composition of fillets

This study evaluated the effects of diets containing Tenebrio molitor larvae meal (TM) on growth performances, somatic indexes, nutrient digestibility and dorsal muscle proximate and fatty acid (FA) compositions of rainbow trout. Three hundred sixty fish were divided into three groups with four replicates each. The groups were fed diets differing in TM inclusion: 0% (TM0), 25% (TM25) and 50% (TM50) on a wet weight basis. Weight gain was not affected by treatment. Feeding rate was significantly higher in TM0 than TM50. Feed conversion ratio was significantly higher in TM0 than TM25 and TM50, while an opposite trend was observed for protein efficiency ratio and specific growth rate. The survival rate was significantly lower in TM0 than TM25 and TM50. The apparent digestibility of protein was significantly lower in the TM50 group than the other groups, while the apparent digestibility of dry matter, organic matter and lipids were unaffected by treatment. If compared to control, the protein and lipid contents of fillets were respectively increased and decreased following TM inclusion in the diet. The n3 / n6 FA ratio of fish dorsal muscle was linearly (TM0 > TM25 > TM50) reduced by TM inclusion in the diet. Results suggest that TM could be used during the growing phase in trout farming; however, additional studies on specific feeding stategies and diet formulations are needed to limit its negative effects on the lipid fraction of fillets.