Modulation of early life gut microbiota through inclusion of earthworms and vermicompost in broiler diets

We previously showed that providing earthworms (EW) to broilers during early life can mitigate dietary challenges induced by soluble non-starch polysaccharides (NSP). However, whether the positive effects of providing EW are associated with changes in the gut microbial communities of broilers was not studied. This follow-up study investigated the influence of providing EW and vermicompost (VC) on gut microbiota diversity in broilers fed either a standard corn-soy based diet as positive control (CON+) or a diet rich in NSP as negative control (CON-). A total of 120 newly hatched male birds of Cobb-500 genotype were examined in two periods (P), each lasting 8 days. In P1, birds were divided into four groups: two groups received the CON+ diet (n = 30 each), the third group received CON+ plus 1 % EW (CON+EW, n = 30), and the last group received CON+ supplemented with 1 % VC (CON+VC, n = 30). Half of the birds in each group were euthanized at the end of P1, and ileal digesta were collected for microbiota analysis. In P2, one of the CON+ groups from P1 continued the same diet, while the remaining groups were switched to dietary challenge either NSP supplemented negative control CON- (n = 15), or CON-EW (n = 15) or CON-VC (n = 15). At the end of P2, the remaining birds in all groups were euthanized for ileal digesta collection. Microbial composition was assessed using 16S rRNA gene sequencing. In P1, the CON+VC exhibited a significantly higher Chao1 index compared to the CON+ and CON+EW (P < 0.05). In P2, α-diversity metrics remained unchanged across groups (P < 0.05), although the Chao1 index in the CON+ showed a trend toward an increase (P = 0.078). Analysis of β-diversity highlighted significant differences between dietary groups in P2 (P = 0.001). Further analysis identified differentially enriched genera, revealing that Enterococcus was prominent in the CON+ during P1, while Lactobacillus was significantly higher in the CON+EW group. In P2, the CON-EW group exhibited increased Lactobacillus abundance while Escherichia-Shigella was overrepresented in the CON- group. Functional analysis showed that the CON-EW and CON-VC diets enriched the pathways related to Nicotinamide Adenine Dinucleotide biosynthesis and fermentation to acetate and lactate, whereas the CON- increased the biosynthesis of enterobactin and aerobactin. In conclusion, dietary earthworm supplementation positively influenced gut microbiota composition and predicted functions in response to dietary challenges.