Total fishmeal replacement by defatted Tenebrio molitor larvae meal induces alterations in intermediary metabolism of European sea bass (Dicentrarchus labrax).

The replacement of fishmeal (FM) by insect meal (IM) in aquafeed formulation has been thoroughly studied lately, but little is known about their impact on nutrient metabolism of fish. This study evaluated the impact not only of partial but also total FM replacement by IM on intermediary metabolism of European sea bass (Dicentrarchus labrax). A fishmeal-based diet was used as a control (CTRL) and two other diets were formulated to include 20% and 40% of defatted Tenebrio molitor larvae meal (dTM), replacing 50% (TM50) and 100% (TM100) of fishmeal (FM), respectively. After a 16-week feeding trial, a multidisciplinary approach including assessment of histological, biochemical, molecular, and enzymatic parameters was adopted to investigate hepatic and plasmatic responses to the different dietary formulations. The results obtained demonstrated that dTM can be successfully used to replace 50% of FM in diets for European sea bass, without adversely affecting liver health or intermediary metabolism of nutrients. As for TM100, although no signs of steatosis were observed in the liver, the activity of glycolytic and lipogenic genes and enzymes increased when compared to CTRL diet (P < 0.05), resulting in higher levels of plasmatic non-esterified fatty acids and triacylglycerides (P < 0.05), which in the long-term may compromise fish health, thus precluding such a high degree of substitution for use in practical diets for European sea bass.