Novel insight into the impact of black soldier fly larvae meal and protease on cecal microbiome, SCFAs, and excreta composition in laying hens.

Abstract

Background: Insect farming represents a sustainable loop that recycles organic wastes back to the food chain while requiring minimal inputs such as land and water. Insect products are not only low in environment footprint, but also nutrient-dense and contain health-promoting bioactives. Black soldier fly larvae meal (BSFLM) stands out as an excellent source of protein and chitin, and the latter is a polysaccharide associated with promoting gut health. A 20-week feeding trial evaluated the effects of three dietary inclusion levels of BSFLM (0%, 6.5%, and 13%), with and without protease enzyme (Concentrase-P) supplementation, on two commercial laying hen strains: Lohmann Brown-Lite (brown hens) and Lohmann LSL-Lite White (white hens). The two strains of 52-week-old hens (mean weight = 2.2 kg) were housed in one production room, with each strain distributed across 36 conventional cages (5 birds per cage). Each treatment was randomly assigned to six cages (n = 6). At the end of the trial, cecal microbiome, SCFA production and excreta composition were studied.

Results: White hens exhibited a distinct cecal microbiome compared to brown hens (p < 0.05), characterized by enhanced diversity, increased relative abundance of Actinobacteriota, and an altered cecal SCFA profile with increased butyric acid and reduced acetic acid levels (p < 0.05). Independent from strain, both 6.5% and 13% BSFLM inclusion promoted cecal microbial richness and evenness, shifting the community to produce more acetic acid and less butyric acid (p < 0.05). Excreta analysis showed significantly higher concentrations and daily excretion of nitrogen, ammoniacal nitrogen and non-ammoniacal nitrogen in both strains on the 13% BSFLM diet. Concentrase-P supplementation effectively ameliorated the elevated nitrogen and ammoniacal nitrogen excretion linked to the 13% BSFLM diet, despite having minimal effects on the cecal microbiome and SCFA production.

Conclusion: Our study provides a novel perspective on the enhanced cecal microbiome diversity in laying hens fed high levels of BSFLM, linking it to suboptimal protein digestion and an undesired increase in protein fermentation, which we have demonstrated can be partially addressed by protease supplementation. Our findings highlight the need to consider interactions between host nutrition, gut microbiome, and sustainability when evaluating novel feed ingredients.