Insect-based diet, a promising nutritional source, modulates gut microbiota composition and SCFAs production in laying hens

Abstract

Insects could be potential nutritional sources both for humans and animals. Among these, Hermetia illucens, with good amount of chitin and proteins, represents a suitable diet replacement for laying hens. Little is known about insect diet effects on the microbial ecology of the gastrointestinal tract and bacterial metabolites production. In this study we investigated the effect of H. illucens larvae meal administration on cecal microbiota and short chain fatty acids (SCFAs) production in laying hens. 16S rDNA sequencing showed strong differences between cecal microbiota of soybean (SD) and insect diet (ID) groups both in type and relative abundance (unweighted and weighted beta diversity) of microbial species. In particular, Bacteroides plebeius, Elusimicrobium minutum, Alkaliphilus transvaalensis, Christensenella minuta, Vallitalea guaymasensis and Flavonifractor plautii represented the principal contributors of changes in gut microbiota composition of ID group (FDR p-values < 0.05). Of these, F. plautii, C. minuta and A. transvaalensis have the potential to degrade the chitin's insect meal and correlated with the observed high levels of gut SCFAs produced in ID group. These microorganisms may thus connect the chitin degradation with high SCFAs production. Our results suggest H. illucens as a potential prebiotic by well feeding gut microbiota.

Figure 1

Cecal microbiota structure after insect-based diet administration. (A) Diversity within SD and ID microbial communities measured by number of observed species and Shannon index. Data are mean ± SEM. Significant differences are indicated by *p < 0.05 and **p < 0.01 (two-sided Student’s two-sample t-test). (B, C) PCoA plots based, respectively, on unweighted and weighted UniFrac distances of SD and ID gut microbial communities (5,234 sequences/sample).

Figure 2

(A) Phylogenetic composition at phylum level of SD and ID microbial communities. (B,C) Relative abundances (%) of bacterial phyla and genera, respectively, found to be significantly different between SD and ID groups (p < 0.05; mean ± SEM). *p < 0.05, **p < 0.01 after FDR correction.

Figure 3

Stacked bar chart showing the count of metagenomic contributors for beta-N-acetylhexosaminidase (K01207) and N-acetylglucosamine-6-phosphate deacetylase (K01443) in SD and ID samples.

Figure 4

SCFAs in cecal samples of ID and SD groups. (A) Stacked bar chart shows mean values of cecal SCFAs in SD and ID groups. (B) Heatmap shows the Pearson’s correlation between SCFAs concentration (y-axis) and key genera at species level identified by SPINGO (bottom, x-axis). Blue and red colors designate, respectively, the positive and negative correlations. *p < 0.05, **p < 0.01, ***p < 0.001.