Hermetia illucens meal inclusion in low-fishmeal diets for rainbow trout (Oncorhynchus mykiss): effects on the growth performance, nutrient digestibility coefficients, selected gut health traits, and health status indices

The impact of diets containing Hermetia illucens meal on the growth, intestinal health, and microbiota of gilthead seabream (Sparus aurata)

The present study investigated the effect of replacing fishmeal (FM) with insect meal of Hermetia illucens (HI) in the diet of Sparus aurata farmed inshore on growth, gut health, and microbiota composition. Two isolipidic (18% as fed) and isoproteic (42% as fed) diets were tested at the farm scale: a control diet without HI meal and an experimental diet with 11% HI meal replacing FM. At the end of the 25-week feeding trial, final body weight, specific growth rate, feed conversion rate, and hepatosomatic index were not affected by the diet. Gross morphology of the gastrointestinal tract and the liver was unchanged and showed no obvious signs of inflammation. High-throughput sequencing of 16S rRNA gene amplicons (MiSeq platform, Illumina) used to characterize the gut microbial community profile showed that Proteobacteria, Fusobacteria, and Firmicutes were the dominant phyla of the gut microbiota of gilthead seabream, regardless of diet. Dietary inclusion of HI meal altered the gut microbiota by significantly decreasing the abundance of Cetobacterium and increasing the relative abundance of the Oceanobacillus and Paenibacillus genera. Our results clearly indicate that the inclusion of HI meal as an alternative animal protein source positively affects the gut microbiota of seabream by increasing the abundance of beneficial genera, thereby improving gut health and maintaining growth performance of S. aurata from coastal farms.

Immune Responses of the Black Soldier Fly Hermetia illucens (L.) (Diptera: Stratiomyidae) Reared on Catering Waste

The black soldier fly (BSF), Hermetia illucens L. (Diptera: Stratiomyidae), has a great bioconversion potential and ability to develop on diverse substrates. Although the use of catering waste and food by-products containing meat and fish would reduce the footprint of the insect sector, to date, in Europe, their use is still facing legal obstacles for insects as food and feed. Since a major request from the EU insect sector is to diversify the spectrum of allowed substrates, and considering that variations in diet composition could influence insect immune responses, we evaluated the impact of different catering wastes on BSF prepupae immunity. Insects were reared on five diets: one based on feed for laying hens and four based on catering waste containing (i) fruits and vegetables; (ii) fruits, vegetables and bread; (iii) fruit, vegetables, bread and dairy products; (iv) fruits, vegetables, bread, meat and fish. The gene expression of two antimicrobial peptides (AMPs), one defensin and one cecropin, was assessed. Moreover, the hemolymph inhibitory activity against Escherichia coli DH5α and Micrococcus yunnanensis HI55 was evaluated using diffusion assays in solid media. The up-regulation of both AMPs' encoding genes was observed in insects fed a bread-added and dairy product-added diet. All hemolymph samples showed inhibitory activity against both bacteria, affecting the colony size and number. The obtained results show how catering waste positively influences the H. illucens immune system. The possibility of modulating AMP expression levels through the diet opens up new perspectives in the management of insect health in mass rearings.

Can Insect Meal Replace Fishmeal? A Meta-Analysis of the Effects of Black Soldier Fly on Fish Growth Performances and Nutritional Values

Simple Summary

Since 2007, black soldier fly meal has become the main substitute suggested in studies to replace fish meal in fish feeds. The quantitative results of these studies have been analyzed in this paper in order to assess the relevance of such substitution. The analysis focused on the impact of this insect on the growth and nutritional quality of fish. The results showed variable conclusions between studies. These variations are due to the fish species or to the protein substitution rate of the fish meal. Although no definite conclusions have been reached, it is possible to consider high levels of substitution.

Abstract

The search for quality alternatives to fishmeal and fish oil in the fish feed industry has occupied many researchers worldwide. The use of black soldier fly meal (BSFM) as a substitute has increased. This study evaluated the effect of this substitution on fish growth and nutritional quality through a meta-analysis of the literature. A list of studies was selected after an exhaustive literature search followed by the extraction of growth and nutritional parameters. Two random-effects models were used to estimate the differences between the experimental parameters and the controls. The results showed significant heterogeneity between studies for all parameters. The sources of heterogeneity between studies were mainly fish species and protein substitution rate. High substitutions can be considered without necessarily worrying about an adverse effect. Financial profitability studies of the fish production chain from BSFM should be carried out to validate or invalidate the economic viability of this substitution.