This study compared serum immunological parameters, cytokines, intestinal permeability, fecal microbiota, and short-chain fatty acids (SCFAs) between healthy and diarrheic suckling calves. Serum and facecal samples were analyzed using ELISA kits, 16S rDNA sequencing, and targeted metabolomics. Compared with healthy calves, the serum levels of aspartate aminotransferase, interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), endotoxin (ET), and diamine oxidase (DAO) were significantly higher (p < 0.05), whereas the serum levels of immunoglobulin A (IgA), immunoglobulin G (IgG), and interleukin-10 (IL-10) were significantly lower in diarrheic calves (p < 0.05). The contents of propionic acid, butyric acid, and valeric acid significantly decreased in the fecal of diarrheic calves (p < 0.05). Moreover, the Chao1 and observed_features index of fecal microbiota significantly decreased in diarrheic calves (p < 0.05). The relative abundance of Escherichia-Shigella, Clostridium_sensu_stricto_1, and Streptococcus was significantly higher (p < 0.05), whereas Phascolarctobacterium, Ruminococcus torques group, and Faecalibacterium were significantly lower in diarrheic calves (p < 0.05). Escherichia-Shigella abundance was positively correlated with ET, DAO, IL-1β, and TNF-α levels (p < 0.05). Faecalibacterium abundance was significantly positively correlated with IgG, IgA, IL-10, and butyric acid but negatively correlated with ET and DAO levels (p < 0.05). In summary, diarrheic suckling calves exhibited reduced immune function, inflammatory response, and increased intestinal permeability. The relative abundance of fecal microbiota of Escherichia-Shigella and Clostridium_sensu_stricto_1 increased, while propionic acid, butyric acid, and valeric acid concentration were decreased in calves with diarrhea. This underscores the critical interplay between microbiota balance and gut health in diarrhea.

Glaesserella parasuis (formerly Haemophilus parasuis, HPS), Actinobacillus pleuropneumoniae (APP), Streptococcus suis (SS), and Pasteurella multocida (PM) are common bacterial pathogens associated with Porcine Respiratory Disease Complex (PRDC), a major cause of economic losses in the swine industry. To address this, a cross-sectional study was conducted across 27 large-scale swine farms in Xinjiang, China (October 2024–May 2025). A total of 1239 clinical samples were analyzed by species-specific PCR, and positive samples were further serotyped. Overall, SS and HPS were the predominant pathogens, with higher detection rates in winter and spring. Notably, SS and HPS were most frequent in nasal swabs, while APP and PM predominated in tissue samples. Furthermore, co-infections were common, with HPS + SS being the most prevalent. Serotyping revealed dominance of HPS serotype 12, APP serotype 12, SS serotype 3, and PM serotypes A and B (serotypes E and F not detected). In addition, SS was also detected in environmental samples and farm workers’ nasal swabs. These findings suggest that future prevention and control strategies should focus on developing multivalent vaccines targeting the predominant serotypes identified, implementing regular serotype surveillance to guide precision immunization protocols, and strengthening environmental disinfection and biosecurity practices to reduce co-infections and occupational exposure risks.

The emergence of antimicrobial resistance in extraintestinal pathogenic Escherichia coli (ExPEC) necessitates alternative therapies for swine. Two lytic phages, vB_EcoM_S37 and vB_EcoP_S37A, were isolated from swine wastewater and characterized for morphology, stability, host range, antibacterial efficacy, and whole-genome features. Optimal multiplicities of infection were 0.01 and 0.1, respectively. Both phages remained stable at pH 4.0–11.0 and 40–60 °C. vB_EcoM_S37 lysed 43.55% (27/62) of tested E. coli strains, with a 5-min latent period and 1173 PFU/cell burst size, and suppressed bacterial growth for 12 h in vitro. vB_EcoP_S37A lysed 6.45% (4/62) of strains, exhibited a 10-min latent period and 210 PFU/cell burst size, and maintained inhibition for 8 h. Genomic analysis revealed that both phages have linear dsDNA genomes devoid of virulence or antibiotic resistance genes. vB_EcoM_S37 (173,927 bp, 37.42% GC) belongs to the genus Mosigvirus (family Straboviridae), whereas vB_EcoP_S37A (38,725 bp, 48.64% GC) represents a novel species within the genus Teseptimavirus (family Autotranscriptaviridae). These findings support both phages as stable, safe, and promising candidates for non-antibiotic biocontrol of ExPEC infections in livestock.