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

Abstract

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.

The Replacement of Fish Meal with Poultry By-Product Meal and Insect Exuviae: Effects on Growth Performance, Gut Health and Microbiota of the European Seabass, Dicentrarchus labrax

“…The comparison of microbial profiles in the gut of PM20 and PM25 fish showed a positive association of the genus Paenibacillus with insect meal. This result confirmed what was previously reported in rainbow trout and gilthead seabream in response to dietary H. illucens meal ingestion [34,35,53]. In contrast, Rangel et al [52] found that consumption of diets enriched with H. illucens exuviae, but not insect meal, led to an increase in the genus Paenibacillus in the gut of European seabass.…”

“…In contrast to the exuviae meal, the amount of insect meal was not sufficient to attenuate the negative effects of PBM on the abundance of lactic acid bacteria. Similarly, in gilthead seabream, a 10% content of H. illucens meal was not sufficient to increase the abundance of lactic acid bacteria in the gut [34,53].…”

“…As a prebiotic, chitin may also increase the biodiversity of the gut microbiota by promoting the proliferation of beneficial chitin-degrading bacteria, such as Bacillus and Paenibacillus, which have recently been isolated from the gastrointestinal tract of European seabass fed chitin-enriched diets [51]. The partial replacement of FM with at least 10% insect meal had an important effect in modulating the transient gut microbial communities by increasing both butyrate-producing bacteria and beneficial lactic acid bacteria [34,35,[52][53][54]. Similarly, the ingestion of H. illucens exuviae meal led to an enrichment of the gut microbiota with the families Bacillaceae, Staphylococcaceae, Paenibacillaceae, and Brevibacteriaceae in seabass and rainbow trout [27,52].…”

“…The qualitative and quantitative determination of SCFAs (acetate, propionate, iso-butyrate, and butyrate) was performed according to the modified extraction method of Chlebicz-Wójcik and Śli żewska [33]. The detailed protocol of SCFA extraction was described by Rimoldi et al [34]. The extracts were analyzed using an HPLC-UV-VIS system (Shimadzu, Milan, Italy) equipped with two LC-20AD pumps, a CBM-Alite controller, a DGU-20A5 degasser, and an automatic injector.…”