Evaluation of an Innovative and Sustainable Pre-Commercial Compound as Replacement of Fish Meal in Diets for Rainbow Trout during Pre-Fattening Phase: Effects on Growth Performances, Haematological Parameters and Fillet Quality Traits

SIMPLE SUMMARY: The study aims to define the potential and sustainable use of pre-commercial product ITTINSECT™ APS V1 as fish meal replacement in the diets of rainbow trout Oncorhynchus mykiss. For this, a 60 days feeding trail was performed by using diets with different replacing rate of fishmeal (0 (ITTM(0)), 25 (ITT(25)), 50 (ITT(50)), 75 (ITT(75)) and 100 (ITT(100)) %) with ITTINSECT™ APS V1. At the end of the feeding trial, significantly higher growth performance was observed in the group fed with the diet with a 25% and 50% substitution of fish meal by ITTINSECT™ APS V1. Moreover, the growth-related gene expressions analyzed in muscle tissue had significantly higher gene expression levels for these two diets (25% and 50% substitution) when compared to the control. The hematology values were found to be identical, whereas other parameters (such as serum total protein, globulins and glucose levels, or some immune-related gene expression) had different results among the experimental groups. In conclusion, replacement of fish meal with up to 50% ITTINSECT™ APS V1 in diets for rainbow trout is suggested in order to achieve the best growth performance in rainbow trout and enhance sustainable aquaculture practices. ABSTRACT: The aim of the study was to determine the potential and sustainable use of pre-commercial product ITTINSECT™ APS V1 as a major protein source in rainbow trout (Oncorhynchus mykiss) diets. A 60-day feeding experiment was conducted to potentially use ITTINSECT as fish meal replacement in the diets of rainbow trout. Five isonitrogenous in dry matter (38% crude protein) and isolipidic (15% crude lipid) diets were produced: a control diet (fishmeal-based) (ITT(0)) and four experimental diets replacing fishmeal by 25 (ITT(25)), 50 (ITT(50)), 75 (ITT(75)) and 100 (ITT(100)) %, with ITTINSECT™ APS V1. Triplicate tanks, containing 15 fish each (65.81 ± 1.26 g), were hand-fed to apparent satiation twice every day during the experiment. At the end of the feeding trial, significantly higher growth performance was observed in the group fed ITTM(25) and ITTM(50) diets. This performance was supported by growth-related gene expressions analyzed in muscle; significantly higher GH and IGF-I genes expression levels were determined in ITT(25) and ITT(50) when compared to control (ITT(0)) (p < 0.05). While no significant differences were found between the hematology values (p > 0.05), serum total protein, globulins and glucose levels were significantly different between experimental groups (p < 0.05). In addition to this, the immune-related genes such as TNF-α, IL8 and IL1-β expression levels were determined to be significantly different (p < 0.05). In conclusion, in order to achieve the best growth performance in rainbow trout and enhance sustainable aquaculture practices, replacement of fish meal with up to 50% ITTINSECT™ APS V1 in diets for rainbow trout is suggested.