Fermented distiller's grains improve broiler immunity and antioxidant capacity by modulating cecal microbiota and cecal/plasma metabolomes.

Fermented distiller's grains (FDG) are rich in nutrients and have high feed utilisation value, but research in broiler feeding is limited. In this experiment, 216 male yellow-feathered broilers (30-day-old, 584.0 ± 3.85 g) were randomly divided into three groups, with six replicates per group and 12 broilers per replicate. The diet treatments were the control group, the 5% FDG group and the 10% FDG group (containing 0%, 5% and 10% FDG to partially replace the concentrates, respectively). The results showed that, compared with the control group, the 5% FDG and 10% FDG groups significantly increased the levels of serum immune index (IgA and IgG), antioxidant index (GSH-Px, SOD and CAT), serum biochemical index (IGF-1), and significantly decreased serum antioxidant index (MDA) of broilers. 16 S rDNA sequencing showed that the 5% FDG and 10% FDG groups altered the cecal microbiota by increasing the abundance of g-UCG-010 (o-Oscillospirales), g-Odoribacter, and g-Oscillospira (associated with short-chain fatty acids production) and decreasing the abundance of the disease-associated bacteria p-Campilobacterota, g-Helicobacter, g-Subdoligranulum and g-Negativibacillus. Metabolomics analysis showed significant changes mainly in lipids and lipid-like molecules, organic acids and derivatives, and organoheterocyclic compounds in the cecum and plasma of broilers from the 5% FDG and 10% FDG groups. Meanwhile, the metabolites altered by feeding FDG were mainly associated with cecal tyrosine metabolism, plasma signal transduction and lipid metabolism in broilers. In conclusion, FDG could improve the immune status and antioxidant capacity of broilers, as well as modulate cecal microbiota, cecal and plasma metabolome, indicating its potential as a beneficial feed ingredient for poultry production.