Changes in the Profile of Fecal Microbiota and Metabolites as Well as Serum Metabolites and Proteome After Dietary Inulin Supplementation in Dairy Cows With Subclinical Mastitis

Nutrition, gastrointestinal microorganisms and metabolites in mastitis occurrence and control

Mastitis affects almost all mammals including humans and dairy cows. In the dairy industry, bovine mastitis is a disease with a persistently high incidence, causing serious losses to the health of cows, the quality of dairy products, and the economy of dairy farms. Although local udder infection caused by the invasion of exogenous pathogens into the mammary gland was considered the main cause of mastitis, evidence has been established and continues to grow, showing that nutrition factors and gastrointestinal microbiome (GM) as well as their metabolites are also involved in the development of mammary inflammatory response. Suboptimal nutrition is recognized as a risk factor for increased susceptibility to mastitis in cattle, in particular the negative energy balance. The majority of data regarding nutrition and bovine mastitis involves micronutrients. In addition, the dysbiotic GM can directly trigger or aggravate mastitis through entero-mammary gland pathway. The decreased beneficial commensal bacteria, lowered bacterial diversity, and increased pathogens as well as proinflammatory metabolites are found in both the milk and gastrointestinal tract of mastitic dairy cows. This review discussed the relationship between the nutrition (energy and micronutrient levels) and mastitis, summarized the role of GM and metabolites in regulating mastitis. Meanwhile, several non-antibiotics strategies were provided for the prevention and alleviation of mastitis, including micronutrients, probiotics, short-chain fatty acids, high-fiber diet, inulin, and aryl hydrocarbon receptor.

Metataxonomic analysis of milk microbiota in the bovine subclinical mastitis

Subclinical mastitis is one of the most widespread diseases affecting dairy herds with detrimental effects on animal health, milk productivity, and quality. Despite its multifactorial nature, the presence of pathogenic bacteria is regarded one of the main drivers of subclinical mastitis, causing a disruption of the homeostasis of the bovine milk microbial community. However, bovine milk microbiota alterations associated with subclinical mastitis still represents a largely unexplored research area. Therefore, the species-level milk microbiota of a total of 75 milk samples, collected from both healthy and subclinical mastitis-affected cows from two different stables, was deeply profiled through an ITS, rather than a traditional, and less informative, 16S rRNA gene microbial profiling. Surprisingly, the present pilot study not only revealed that subclinical mastitis is characterized by a reduced biodiversity of the bovine milk microbiota, but also that this disease does not induce standard alterations of the milk microbial community across stables. In addition, a flow cytometry-based total bacterial cell enumeration highlighted that subclinical mastitis is accompanied by a significant increment in the number of milk microbial cells. Furthermore, the combination of the metagenomic and flow cytometry approaches allowed to identify different potential microbial marker strictly correlated with subclinical mastitis across stables.

The 16S rDNA high-throughput sequencing correlation analysis of milk and gut microbial communities in mastitis Holstein cows

This study aimed to understand the changes in the milk and gut microbiota of dairy cows with mastitis, and to further explore the relationship between mastitis and the microbiota. In this study, we extracted microbial DNA from healthy and mastitis cows and performed high-throughput sequencing using the Illumina NovaSeq sequencing platform. OTU clustering was performed to analyze complexity, multi-sample comparisons, differences in community structure between groups, and differential analysis of species composition and abundance. The results showed that there were differences in microbial diversity and community composition in the milk and feces of normal and mastitis cows, where the diversity of microbiota decreased and species abundance increased in the mastitis group. There was a significant difference in the flora composition of the two groups of samples (P < 0.05), especially at the genus level, the difference in the milk samples was Sphingomonas (P < 0.05) and Stenotrophomonas (P < 0.05), the differences in stool samples were Alistipes (P < 0.05), Flavonifractor (P < 0.05), Agathobacter (P < 0.05) and Pygmaiobacter (P < 0.05). In conclusion, the microbiota of the udder and intestinal tissues of dairy cows suffering from mastitis will change significantly. This suggests that the development of mastitis is related to the endogenous pathway of microbial intestinal mammary glands, but the mechanisms involved need further study.

Gill Junction Injury and Microbial Disorders Induced by Microcystin-Leucine Arginine in Lithobates catesbeianus Tadpoles

Microcystin-LR (MC-LR) is widely present in waters around the world, but its potential toxic effects and mechanisms on amphibian gills remain unknown. In the present study, tadpoles (Lithobates catesbeianus) were exposed to environmentally realistic concentrations of 0.5, 2 μg/L MC-LR, and 0 μg/L MC-LR (Control) for 30 days with the objective to unveil the impairment of gill health. The lysozyme was downregulated, while pattern recognition receptors and complement and adaptive immune processes were upregulated and the ability of gill supernatant to inhibit pathogenic bacteria decreased in the 0.5 and 2 μg/L MC-LR groups. The transcriptions of epithelial barrier components (e.g., CLDN1) were significantly decreased in MC-LR-exposed gills, while the gill content of lipopolysaccharide (LPS) endotoxins and the transcriptions of downstream responsive genes (e.g., TLR4 and NF-κB) were concurrently increased. In addition, the number of eosinophils and the expression of pro-inflammatory cytokines (e.g., IL-1β and TNF-α) were increased. These results imply that exposure of tadpoles to low environmentally concentrations of MC-LR leads to inflammation, increased permeability, and a reduced ability to inhibit pathogenic bacteria. The epithelial cells of inner gill filaments increased and transcriptions of hypoxic stress genes (e.g., HIF-1α, FLT1, and SERPINE1) were upregulated within the exposed group. As a consequence, exposure to MC-LR may lead to hypoxic stress. MC-LR exposure also drove gill microbiota to a dysbiosis. The relative abundance of Elizabethkingia was positively correlated with content of LPS and transcriptions of NF-κB and TNF-α. Overall, this study presents the first evidence about the pronounced impacts of MC-LR exposure on gills of amphibians, highlighting the susceptibility of early developing tadpoles to the environmental risks of MC-LR.