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Exploratory Shotgun Metagenomic Analysis of the Fecal Microbiome and Antimicrobial-Resistance Potential in Simmental Calves with Different Diarrheal Statuses

Year: 2026

Type: article

Abstract: Calf diarrhea is frequently accompanied by disruption of the gastrointestinal microbiota, but the relationships between clinical status and microbial community composition, gene-content functional potential, and antimicrobial-resistance-associated features remain incompletely characterized. This exploratory study aimed to characterize these features in calves with different diarrheal statuses using shotgun metagenomics. Six approximately 2-month-old Simmental calves from Chahar Right Middle Banner, Inner Mongolia, were included, comprising two healthy calves, two calves with mild diarrhea, and two calves with severe diarrhea. Read-based taxonomic profiling was complemented by gene-abundance-weighted taxonomic annotation, and microbial functional potential was characterized using eggNOG/COG, KEGG, and CAZy annotations, together with conservatively screened CARD-associated sequence-homology candidates. The two severe-diarrhea samples exhibited lower bacterial richness and Shannon diversity, although PCoA did not show clear separation according to clinical severity. These two samples showed high representation of Proteobacteria and Enterobacteriaceae-related taxa, particularly Escherichia-related assignments, together with lower representation of Ruminococcaceae, Faecalibacterium, and Prevotella. Gene-content profiles showed higher representation of selected functions related to transport, environmental sensing, motility, secretion, and bacterial cell-envelope processes, whereas several glycan- and complex-carbohydrate-associated functions showed lower representation. Selected CARD-associated candidates were also more abundant in the severe-diarrhea samples. Within this small exploratory cohort, the two severe-diarrhea samples therefore showed concordant taxonomic and gene-content differences; however, these observations should not be interpreted as a general severity-specific microbiome signature and require validation in larger longitudinal cohorts.

Source: Microorganisms

DOI: 10.3390/microorganisms14102370