Abstract
Simple SummaryThe sustainability of fish production is mainly driven by the protein source used in aquafeeds. In conventional fish feed, protein sources are mostly vegetable ingredients and fishmeal. The present study explored the potential use of full-fat Hermetia illucens prepupae meal (H) replacing 0% (H0), 25% (H25), and 50% (H50) conventional ingredients in practical diets for rainbow trout. No significant differences in growth were observed in all experimental groups, while in fish fed the H50 diet both hepatic and intestinal alterations were detected. In addition, in the same fish group, genes related to stress and immune-response were significantly up-regulated. The results obtained so far highlighted an overall physiological adaptation of fish to the dietary manipulation, suggesting an adverse effect of full-fat H at the highest inclusion level.This study investigated the effects of dietary inclusion levels of full-fat Hermetia illucens prepupae meal (H) on growth and gastrointestinal integrity in rainbow trout (Oncorhynchus mykiss). A 98-day study was conducted using triplicate groups of trout (initial body weight, 137 ± 10.5 g) kept in 1-m3 tanks in a flow-through well water system. Three dietary treatments were prepared: one based on fishmeal and purified protein-rich vegetable ingredients (H0), and two experimental diets including graded levels of H meal (25% and 50%, referred to as H25 and H50, respectively). At the end of the feeding trial, no differences were observed in growth performance and plasma metabolite levels, with the biometric data confirmed by the liver expression of the genes involved in somatic growth regulation (igf1 and mstn1a). In the H50 group, a three-fold up regulation of liver hsp70 was observed. An activation of the stress/immune response (il-10, tnf-α, and tlr-5) was observed in medium intestine in the H25 and H50 groups (p < 0.05) together with a villi length reduction detected through histological analyses. Liver histology and Fourier Transform Infrared Imaging (FTIRI) spectroscopy highlighted an increase in lipid deposition. These findings suggest that caution should be taken into account when 50% replacement of conventional ingredients with H is selected.
Highlights
One of the most critical issues that threatens the sustainability and further growth of intensive aquaculture of carnivorous species is its dependency on fishmeal (FM) and fish oil (FO) in aquafeed [1].alternative ingredients are needed to promote a sustainable aquaculture production while improving fish growth and health performance [2]
Over the last two decades, research efforts have focused on the reduction of the dietary inclusion levels of FM and FO by replacement with plant protein sources and vegetable oils, which are readily available on the feed market and cost-effective [1]
Fish fed both diets containing insects (H25 and H50) resulted in a final body weight (FBW), K, weight gain (WG), specific growth rate (SGR) and feed conversion ratio (FCR) that were not significantly different (p > 0.05) from those attained by fish fed the H0 diet
Summary
One of the most critical issues that threatens the sustainability and further growth of intensive aquaculture of carnivorous species is its dependency on fishmeal (FM) and fish oil (FO) in aquafeed [1]. Alternative ingredients are needed to promote a sustainable aquaculture production while improving fish growth and health performance [2]. Some alternatives include animal feedstuffs, comprising both non-ruminant slaughterhouse by-products (derived from processed animal proteins, PAPs) and insect meals [6,7]. Insect meals have a low ecological footprint [8], high feed conversion efficiency [9], and, together with PAPs, can reasonably foster a circular bio-economy
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