Partial and total fishmeal replacement by defatted Tenebrio molitor larvae meal do not alter short- and mid-term regulation of food intake in European sea bass (Dicentrarchus labrax)

Understanding the underlying mechanisms responsible for regulation of food intake in fish is crucial for proper formulation of aquafeeds and consequently ensure the best growth performance of fish. Over the last decade, the study of the impact of insect meal-based diets on growth performance and voluntary feed intake of several fish species has emerged, but little is known about their influence on anorexigenic potential. This is the first study evaluating short- and mid-term responses of European sea bass (Dicentrarchus labrax) fed diets not only with partial, but also with total fishmeal (FM) replacement by defatted Tenebrio molitor larvae meal (dTM). A fishmeal-based diet was used as a control (CTRL) and two other diets were formulated to include 20% and 40% of dTM, replacing 50% and 100% of fishmeal (FM), respectively. The short-term response was evaluated after the first exposure to the experimental diets, whereas the mid-term response was evaluated after 7 days of feeding. In both short- and mid-term trials, food intake was registered. Hepatic and plasmatic metabolites and the expression of hypothalamic and telencephalic neuropeptides involved in food intake were assessed 2 and 24 h post-feeding. No differences occurred in food intake levels, neither in the short- nor mid-term. In the short-term, plasmatic glucose levels increased in fish fed TM100, regardless post-feeding sampling time. In the mid-term, fish fed TM100 had the highest levels of triglycerides in liver and the lowest levels of α-amino-acids in plasma, irrespective of post-feeding sampling time. At central level, dietary treatment did not alter the expression of neuropeptide Y (npy), agouti-related protein 2 (agrp2), pro-opio melanocortin a (pomca) or cocaine- and amphetamine-related transcript 2 (cartpt2) in hypothalamus and telencephalon. The obtained results suggest that partial and total FM replacement by dTM does not influence short- and mid-term regulation of food intake in European sea bass. Nonetheless, changes observed in hepatic and plasmatic metabolite levels of fish fed TM100 may indicate alterations of intermediary metabolism in the long-term.