Effect of feeding with insect meal diet on the fatty acid compositions of sea bream (Sparus aurata), tench (Tinca tinca) and rainbow trout (Oncorhynchus mykiss) fillets

Abstract Currently, insects are considered a new source of food that could be an alternative to fishmeal (FM) in aquaculture. However, more studies are needed to assess the effects of the inclusion of insects in fish diets on both fish productivity and fish quality. To this end, three trials were conducted to evaluate as feed ingredients the meals of two insects, black soldier fly (Hermetia illucens, HI) and mealworm (Tenebrio molitor, TM), on the fatty acid (FA) profiles of fillets of three fish species: sea bream (Sparus aurata), tench (Tinca tinca) and rainbow trout (Oncorhynchus mykiss). In each trial, the animals were randomly divided into five experimental groups (3 tanks/treatment). The fish were fed until triple their initial weight with isoprotein and isolipid diets at different levels of FM replacement using insect meal: 0% insect meal or control diet (C), 15% inclusion of HI meal (H15), 30% inclusion of HI meal (H30), 15% inclusion of TM meal (T15), and 30% inclusion of TM meal (T30). Overall, the use of insect meal induced a decrease in valuable long chain polyunsaturated fatty acids (LCPUFAs) in fish fillets, and the higher the insect inclusion (H30 and T30 diets), the higher the decreases in EPA and DHA contents. Moreover, insect-containing diets worsened the lipid health indices (n-3/n-6 ratio, atherogenicity AI, and thrombogenicity TI indices) of fillets. However, differences between the three fish species were observed: tench was the more resilient species to insect inclusion, while in rainbow trout, there were very marked decreases in LCPUFA content, especially in DHA, and in the n-3/n-6 ratio. Nevertheless, insect-fed fish could be considered “healthy” based on the n-3 LCPUFA content. Furthermore, several strategies could be implemented to avoid the decline of n-3 LCPUFAs in fish, such as using partially defatted insect meal or the use of insects previously fed n-3 PUFA-rich by-products.