Different Diets Based on Yellow Mealworm (Tenebrio molitor)—Part A: Facing the Decrease in Omega−3 Fatty Acids in Fillets of Rainbow Trout (Oncorhynchus mykiss)

Abstract

Aquaculture struggles with sustainability due to the use of fishmeal, and insects are one potential alternative. Insects have low long-chain omega−3 polyunsaturated fatty acid content, and insect-fed fish reflect this in their composition. In total, 500 rainbow trout (Oncorhynchus mykiss, ~46 g) were fed until the fish reached a commercial size (~415 g). Five diets were used: one control based on fishmeal as main source of protein; two with a 50% replacement of fishmeal with yellow mealworm meal (Tenebrio molitor), one with full-fat insect, and another partially defatted; two other diets similar to the one with the full-fat insect, but with the addition of an experimental algal oil rich in omega−3 in two different concentrations (one equivalent to control, the other one to the defatted insect diet). Growth was unaffected, as well as texture and organoleptic profile of the fillets. Lightness, brightness and colour of the fillets were slightly modified by the experimental diets. An increase in omega−3 levels over those of the full-fat insect diet is described. An omega−3 sparing effect was highlighted, causing lipid accumulation in fillets and liver, and a mild increase in oxidative damage. More research is encouraged to evaluate the fatty acid profile of the liver.