Partially Alternative Feeding with Fermented Distillers’ Grains Modulates Gastrointestinal Flora and Metabolic Profile in Guanling Cattle

SIMPLE SUMMARY: Fermented distillers’ grains are a common dietary supplement for livestock and poultry, aimed at improving health and metabolism. Despite this, there is a lack of studies examining the effect of fermented distillers’ grains intake on the gastrointestinal microbiota and metabolites in cattle. The objective of this study was to examine the effects of partially substituting traditional feed with fermented distillers’ grains on the gastrointestinal flora and metabolic profile of Guanling cattle. The results indicate that the fermented distillers’ grains replacement diet altered the microbial community structure in the abomasum and cecum of the cattle. Furthermore, it increased the abundance of probiotics while decreasing the abundance of potential pathogenic bacteria, thereby improving the overall gastrointestinal health of the cattle to some extent. The differential metabolites present in the abomasum and cecum contents of Guanling cattle demonstrated a significant enrichment in metabolic pathways, including primary bile acid biosynthesis and choline metabolism in cancer. Moreover, a noteworthy correlation was observed between the differential metabolites and the differential bacterial genera. This study’s outcomes offer a scientific reference for the potential employment of FDG as a feed resource in cattle. ABSTRACT: Fermented distillers’ grains (FDG) are commonly used to enhance the health and metabolic processes of livestock and poultry by regulating the composition and activity of the intestinal microbiota. Nevertheless, there is a scarcity of research on the effects of the FDG diet on the gastrointestinal microbiota and its metabolites in cattle. This study examines the impact of FDG dietary supplements on the gastrointestinal flora and metabolic profile of Guanling cattle. Eighteen cattle were randomly assigned to three treatment groups with six replicates per group. The treatments included a basal diet (BD), a 15% concentrate replaced by FDG (15% FDG) in the basal diet, and a 30% concentrate replaced by FDG (30% FDG) in the basal diet. Each group was fed for a duration of 60 days. At the conclusion of the experimental period, three cattle were randomly chosen from each group for slaughter and the microbial community structure and metabolic mapping of their abomasal and cecal contents were analyzed, utilizing 16S rDNA sequencing and LC-MS technology, respectively. At the phylum level, there was a significant increase in Bacteroidetes in both the abomasum and cecum for the 30%FDG group (p < 0.05). Additionally, there was a significant reduction in potential pathogenic bacteria such as Spirochetes and Proteobacteria for both the 15%FDG and 30%FDG groups (p < 0.05). At the genus level, there was a significant increase (p < 0.05) in Ruminococcaceae_UCG-010, Prevotellaceae_UCG-001, and Ruminococcaceae_UCG-005 fiber degradation bacteria. Non-target metabolomics analysis indicated that the FDG diet significantly impacted primary bile acid biosynthesis, bile secretion, choline metabolism in cancer, and other metabolic pathways (p < 0.05). There is a noteworthy correlation between the diverse bacterial genera and metabolites found in the abomasal and cecal contents of Guanling cattle, as demonstrated by correlation analysis. In conclusion, our findings suggest that partially substituting FDG for conventional feed leads to beneficial effects on both the structure of the gastrointestinal microbial community and the metabolism of its contents in Guanling cattle. These findings offer a scientific point of reference for the further use of FDG as a cattle feed resource.