Resilience of the ruminal bacterial community to increasing inclusion of de-oiled wet distillers grains in feedlot diets

Abstract

This study aimed to evaluate the impact of increasing de-oiled wet distillers grains (WDG) inclusion on the structure, diversity, and composition of the ruminal bacterial community in Nellore cattle fed high-concentrate diets. Four ruminally cannulated Nellore bulls were assigned to a 4 × 4 Latin square design and fed diets containing 0, 150, 300, or 450 g de-oiled WDG/kg dry matter. Ruminal samples were collected for bacterial DNA extraction and 16S rRNA gene amplicon sequencing to assess alpha diversity, beta diversity, and taxonomic composition. Increasing dietary inclusion of de-oiled WDG did not affect bacterial richness ( P = 0.35) or overall community structure ( P = 0.26). Permutational multivariate analysis of variance revealed no significant treatment effects on bacterial community structure ( P > 0.05), indicating high microbial stability across diets. Relative abundance analysis showed that Firmicutes and Bacteroidetes remained the dominant phyla across all treatments, with no significant differences detected after multiple-testing correction ( P > 0.05). Exploratory analyses identified a limited number of taxa contributing to between-treatment dissimilarities, mainly affiliated with Firmicutes , Bacteroidetes , Verrucomicrobia , and Chloroflexi ; however, none of these differences remained significant after false discovery rate adjustment. Overall, increasing inclusion of de-oiled WDG in high-concentrate diets did not induce substantial shifts in the ruminal bacterial community. These findings suggest that the rumen microbiome of feedlot Nellore cattle is resilient to dietary replacement of conventional ingredients with de-oiled WDG up to 450 g/kg DM, supporting its practical application as a sustainable coproduct in intensive beef production systems without compromising microbial ecosystem stability.

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