Growth and Welfare of Rainbow Trout (Oncorhynchus mykiss) in Response to Graded Levels of Insect and Poultry By-Product Meals in Fishmeal-Free Diets

Abstract

This study compared the nutrient-energy retention, digestive function, growth performance, and welfare of rainbow trout (ibw 54 g) fed isoproteic (42%), isolipidic (24%), fishmeal-free diets (CV) over 13 weeks. The diets consisted of plant-protein replacement with graded levels (10, 30, 60%) of protein from poultry by-product (PBM) and black soldier fly H. illucens pupae (BSFM) meals, either singly or in combination. A fishmeal-based diet was also tested (CF). Nitrogen retention improved with moderate or high levels of dietary PBM and BSFM relative to CV (p < 0.05). Gut brush border enzyme activity was poorly affected by the diets. Gastric chitinase was up-regulated after high BSFM feeding (p < 0.05). The gut peptide and amino acid transport genes were differently regulated by protein source and level. Serum cortisol was unaffected, and the changes in metabolites stayed within the physiological range. High PBM and high BSFM lowered the leukocyte respiratory burst activity and increased the lysozyme activity compared to CV (p < 0.05). The BSFM and PBM both significantly changed the relative percentage of lymphocytes and monocytes (p < 0.05). In conclusion, moderate to high PBM and BSFM inclusions in fishmeal-free diets, either singly or in combination, improved gut function and nutrient retention, resulting in better growth performance and the good welfare of the rainbow trout.

Effects of Dietary Plant Protein Replacement with Insect and Poultry By-Product Meals on the Liver Health and Serum Metabolites of Sea Bream (Sparus aurata) and Sea Bass (Dicentrarchus labrax)

“…Histological investigations represent an initial step in detecting potential changes associated with inflammation, degeneration, and cell death. These investigations are crucial for assessing the effects of novel diet formulations in feeding trials on liver metabolism and health [48,49,79].…”

“…A set of metabolic parameters, including glucose (GLU), triglycerides (TAGs), cholesterol (CHO), total protein (TP), albumin (ALB), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) were analyzed on serum samples using an automated biochemistry analyzer (BPC BIOSED, Rome, Italy) and commercial kits (Giesse Diagnostics, Rome, Italy), according to Cardinaletti et al [79].…”

Use of grape by-products in aquaculture: New frontiers for a circular economy application

“…This especially occurred at a time when fish diets have begun to be replaced with vegetable sources and ingredients alternatives to conventional ones, with the aim of limiting the competition of fish stocks [ 44 ]. The most used alternative feedstuffs are soybean meal, which very often caused intestinal inflammation, modulating microbiota and histology [ 45 , 46 ], poultry by-products and insects meals [ 47 , 48 ]. Also for the grape by-products, numerous studies investigated on the effects of their substitution or their use as additives at intestinal level and as consequence both in growth performances and in mitigation soybean meal subacute enteritis-induced [ 49 ] .…”

Enhanced protein degradation by black soldier fly larvae (Hermetia illucens L.) and its gut microbes

“…Edible insect BSFL is a quality protein resource that can be used as a feed protein supplement for fisheries, poultry. It is of great significance for alleviating animal feed protein shortage ( Cardinaletti et al, 2022 ; Lu, S. et al, 2022 ; Cheng et al, 2023 ). The addition of microbes can improve the organic waste conversion efficiency of BSFL ( Zhang et al, 2021 ).…”