Subclinical mastitis is a common disease that threatens the welfare and health of dairy cows and causes huge economic losses. Somatic cell count (SCC) is the most suitable indirect index used to evaluate the degree of mastitis. To explore the relationship between SCC, diversity in the microbiome, and subclinical mastitis, we performed next-generation sequencing of the 16S rRNA gene of cow’s milk with different SCC ranges. The data obtained showed that the microbiota was rich and coordinated with SCC below 2 × 10⁵. SCC above 2 × 10⁵ showed a decrease in the diversity of microbial genera. When SCC was below 2 × 10⁵, the phylum Actinobacteriota accounted for the most. When SCC was between 2 × 10⁵ and 5 × 10⁵, Firmicutes accounted for the most, and when SCC exceeded 5 × 10⁵, Firmicutes and Proteobacteria accounted for the most. Pathogenic genera such as Streptococcus spp. were absent, while SCC above 2 × 10⁵ showed a decrease in the diversity of microbial genera. SCC was positively correlated with the percentage of Romboutsia, Turicibacter, and Paeniclostridium and negatively correlated with the percentage of Staphylococcus, Psychrobacter, Aerococcus, and Streptococcus. Romboutsia decreased 6.19 times after the SCC exceeded 2 × 10⁵; the SCC increased exponentially from 2 × 10⁵ to 5 × 10⁵ and above 1 × 10⁶ in Psychrobacter. Analysis of the microbiota of the different SCC ranges suggests that the development of mastitis may not only be a primary infection but may also be the result of dysbiosis in the mammary gland.

Chlorine dioxide is a globally recognized green and efficient disinfectant. This study aims to investigate the bactericidal mechanism of chlorine dioxide using beta-hemolytic Streptococcus (BHS) CMCC 32210 as a representative strain. BHS was exposed to chlorine dioxide, the minimum bactericidal concentration (MBC) values of chlorine dioxide against BHS were determined by the checkerboard method in preparation for subsequent tests. Cell morphology was observed using electron microscopy. Protein content leakage, adenosine triphosphatase (ATPase) activity, and lipid peroxidation were determined by kits, and DNA damage was determined using agar gel electrophoresis. The concentration of chlorine dioxide during disinfection showed a linear relationship with the concentration of BHS. Scanning electron microscopy (SEM) results showed that chlorine dioxide caused significant damage to the cell walls of BHS at a concentration of 50 mg/L, but had no significant effect on Streptococcus exposed to different exposure times. Furthermore, the extracellular protein concentration increased with increasing chlorine dioxide concentration, while the total protein content remained unchanged. The activities of Na⁺/K⁺-ATPase and Ca²⁺/Mg²⁺-ATPase decreased with increasing chlorine dioxide concentration. Chlorine dioxide treatment led to significant lipid peroxidation and DNA degradation in BHS. Leakage of intracellular components indicated that chlorine dioxide damaged the cell membrane of BHS. Chlorine dioxide exposure resulted in oxidative damage to lipids and proteins, which negatively impacted the cell wall and membrane of Streptococcus. This caused increased permeability and inactivation of key enzymes (Na⁺/K⁺-ATPase and Ca²⁺/Mg²⁺-ATPase) involved in respiratory metabolism, ultimately leading to DNA degradation and bacterial death due to either content leakage or metabolic failure.

This study evaluated the clinical bactericidal efficacy and safety of a novel chlorine dioxide teat disinfectant compared to a traditional iodine glycerin disinfectant in dairy cows. The randomized controlled trial included long-term natural exposure (100 cows) and teat surface disinfection (40 cows) experiments. Key metrics assessed were somatic cell count (SCC), teat skin health (dryness, roughness, hyperkeratosis), and bacterial reduction rates against Staphylococcus aureus, Escherichia coli, and Streptococcus spp. Results demonstrated that the chlorine dioxide teat disinfectant achieved comparable to iodine glycerin disinfectant in controlling the rate of SCC exceeding the threhold (3.57% vs. 4.50% at day 10; p > 0.05), teat skin dryness, end roughness, and hyperkeratosis severity showed no significant differences over time or between iodine glycerin (control) and chlorine dioxide teat disinfectant groups (all p > 0.05). Notably, quantitative bacteriological assessment revealed significantly higher log₁₀ reduction values for chlorine dioxide teat disinfectant (2.14) versus iodine glycerin controls (1.93; p < 0.05). Microbiological evaluation further demonstrated complete pathogen eradication (100.00%) by chlorine dioxide across all isolates (S. aureus, E. coli, Streptococcus spp.), whereas iodine glycerin achieved 99.84–100.00% bactericidal rates. The findings suggest that chlorine dioxide teat disinfectant is a sustainable and effective alternative to iodine glycerin disinfectant, offering robust antimicrobial activity, improved teat condition, and reduced residue concerns. Further multicenter studies are warranted to validate these outcomes under diverse herd management conditions.

Lumpy skin disease virus (LSDV), a capripoxvirus that causes substantial animal-health and economic losses in cattle, remains a major veterinary concern, with few specific antiviral options available. Here, a series of semi-synthetic Tylosin A derivatives were evaluated for anti-LSDV activity using an LSDV-eGFP infection model in Madin–Darby bovine kidney cells. Initial screening identified T3 and T8 as the most active derivatives, reducing infectious virus production by 89.6% and 91.0%, respectively, at 200 ppm. Dose–response analysis based on infectious-virus titration yielded IC₅₀ values of 23.02 ppm (95% CI, 18.48–28.33) for T3 and 19.13 ppm (95% CI, 13.87–25.32) for T8. The corresponding CC₅₀ values were 748.3 and 621.4 ppm, resulting in selectivity indices of 32.50 and 32.48, respectively. Mechanistic studies focusing on T3 showed that antiviral activity was most pronounced when the compound was administered after viral entry and during the early post-infection period. T3 reduced viral genomic DNA accumulation beginning at 8 h post-infection while largely preserving early viral gene transcription and suppressing DNA-replication-dependent intermediate and late gene expression. This phenotype closely resembled that induced by the DNA synthesis inhibitor cytarabine (AraC), supporting an inhibitory effect of T3 at or upstream of the viral DNA replication stage. Proteome-wide molecular docking did not reveal preferential docking of T3 to the selected viral DNA replication-associated proteins, and direct target engagement remains to be established. Collectively, these findings identify T3 and T8 as promising anti-LSDV lead compounds and support further optimization of the Tylosin A scaffold, while mechanistic studies suggest that T3 exerts its antiviral effects primarily during the viral DNA replication phase.