Consumption of Supplementary Inulin Modulates Milk Microbiota and Metabolites in Dairy Cows with Subclinical Mastitis

Microbiome and metabolome analyses of milk and feces from dairy cows with healthy, subclinical, and clinical mastitis

Mastitis is commonly recognized as a localized inflammatory udder disease induced by the infiltration of exogenous pathogens. In the present study, our objective was to discern fecal and milk variations in both microbiota composition and metabolite profiles among three distinct groups of cows: healthy cows, cows with subclinical mastitis and cows with clinical mastitis. The fecal microbial community of cows with clinical mastitis was significantly less rich and diverse than the one harbored by healthy cows. In parallel, mastitis caused a strong disturbance in milk microbiota. Metabolomic profiles showed that eleven and twenty-eight molecules exhibited significant differences among the three groups in feces and milk, respectively. Similarly, to microbiota profile, milk metabolome was affected by mastitis more extensively than fecal metabolome, with particular reference to amino acids and sugars. Pathway analysis revealed that amino acids metabolism and energy metabolism could be considered as the main pathways altered by mastitis. These findings underscore the notable distinctions of fecal and milk samples among groups, from microbiome and metabolomic points of view. This observation stands to enhance our comprehension of mastitis in dairy cows.

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.

Lactobacillus reuteri inhibits Staphylococcus aureus-induced mastitis by regulating oxytocin releasing and gut microbiota in mice

Mastitis is the most frequent disease of cows and has well-recognized detrimental effects on animal wellbeing and dairy farm profitability. With the advent of the postantibiotic era, alternative antibiotic agents, especially probiotics, have received increasing attention in the treatment of mastitis. Based on research showing that Lactobacillus reuteri (L. reuteri) has anti-inflammatory effects, this study explored the protective effects and mechanisms of L. reuteri against mastitis induced by Staphylococcus aureus (S. aureus) in mice. First, mice with S. aureus-induced mastitis were orally administered L. reuteri, and the inflammatory response in the mammary gland was observed. The results showed that L. reuteri significantly inhibited S. aureus-induced mastitis. Moreover, the concentration of oxytocin (OT) and protein expression of oxytocin receptor (OTR) were measured, and inhibition of OTR or vagotomy reversed the protective effect of L. reuteri or its culture supernatant (LCS) on S. aureus-induced mastitis. In addition, in mouse mammary epithelial cells (MMECs), OT inhibited the inflammation induced by S. aureus by inhibiting the protein expression of OTR. It was suggested that L. reuteri protected against S. aureus-induced mastitis by releasing OT. Furthermore, microbiological analysis showed that the composition of the microbiota was altered, and the relative abundance of Lactobacillus was significantly increased in gut and mammary gland after treatment with L. reuteri or LCS. In conclusion, our study found the L. reuteri inhibited the mastitis-induced by S. aureus via promoting the release of OT, and treatment with L. reuteri increased the abundance of Lactobacillus in both gut and mammary gland.

Altered rumen microbiome and correlations of the metabolome in heat-stressed dairy cows at different growth stages

IMPORTANCE

Heat stress is one of the main causes of economic losses in the dairy industry worldwide; however, the mechanisms associated with the metabolic and microbial changes in heat stress remain unclear. Here, we characterized both the changes in metabolites, rumen microbial communities, and their functional potential indices derived from rumen fluid and serum samples from cows at different growth stages and under different climates. This study highlights that the rumen microbe may be involved in the regulation of lipid metabolism by modulating the fatty acyl metabolites. Under heat stress, the changes in the metabolic status of growing heifers, heifers, and lactating cows were closely related to arachidonic acid metabolism, fatty acid biosynthesis, and energy metabolism. Moreover, this study provides new markers for further research to understand the effects of heat stress on the physiological metabolism of Holstein cows and the time-dependent changes associated with growth stages.

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.

Inulin-induced differences on serum extracellular vesicles derived miRNAs in dairy cows suffering from subclinical mastitis

MicroRNA (miRNA) profiles vary with the nutritional and pathological conditions of cattle. In this study, we aimed to investigate the effects of inulin supplement on miRNA profiles derived from serum extracellular vesicles (EVs). Our goal was to determine the differences in miRNA expressions and analyse the pathways in which they are involved. Based on the results of California mastitis test and milk somatic cell counts, ten lactating cows with subclinical mastitis were randomly divided into two groups: an inulin group and a control group (n = 5 in each group). The inulin group received a daily supplement of 300 g of inulin while the control group did not receive any supplementation. After a 5-week treatment period, serum-derived EV-miRNAs from each cow were isolated. High-throughput sequencing was conducted to identify differentially expressed miRNAs. GO and KEGG bioinformatics analysis was performed to examine the target genes of these differentially expressed miRNAs. The EV-RNA concentration and small RNA content were not affected by the inulin treatment. A total of 162 known miRNAs and 180 novel miRNAs were identified from 10 samples in the two groups. Among the known miRNAs, 23 miRNAs were found to be differentially expressed between the two groups, with 18 upregulated and five downregulated in the inulin group compared to the control group. Pathway analysis revealed the involvement of these differentially expressed miRNAs in the regulation of cell structure and function, lipid oxidation and metabolism, immunity and inflammation, as well as digestion and absorption of nutrients. Overall, our study provides a molecular-level explanation for the reported beneficial health effects of inulin supplementation in cows with subclinical mastitis.

Hericium caput-medusae (Bull.:Fr.) Pers. fermentation concentrate polysaccharides improves intestinal bacteria by activating chloride channels and mucus secretion

ETHNOPHARMACOLOGICAL RELEVANCE

As a traditional edible fungus in China and many other Asian countries, Hericium caput-medusae (Bull. Fr.) Pers. is widely used to improve the health of the gastrointestinal tract. For example, the drug "Weilexin Granules" is mainly composed of H. caput-medusae (Bull. Fr.) Pers. fermentation concentrate. However, the mechanism of action remains to be elucidated.

AIMS OF THE STUDY

The purpose of this study was to assess whether polysaccharides from H. caput-medusae (Bull. Fr.) Pers. fermentation concentrate (HFP) exerts a gut protective effect and a regulatory effect on the intestinal microbiota through the chloride channels and mucus secretion.

MATERIALS AND METHODS

HFP was extracted, characterized and different concentrations of HFP (100, 200, 400 mg/kg) were administered to mice for 14 days. The changes in gut microbiota were observed via 16S high throughput sequencing. Short-chain fatty acids (SCFAs) was detected by GC-MS. AB-PAS staining was used to observe the secretion of mucus. The chloride channel activity and protein expression were verified by short-circuit current measurement and Western blot.

RESULTS

HFP regulated the abundance of gut microbiota in mice, with increased levels of Ruminococcaceae and Lachnospiraceae and reduced proportions of Staphylococcus and Enterobacter. HFP enhanced mucus volume as well as increased intestinal fluid secretion by activating the chloride channels. In addition, short-circuit current experiments also proved that HFP activates Cl⁻ currents targeting cystic fibrosis transmembrane conductance regulator (CFTR) and Anoamin1 (ANO1).

CONCLUSION

In conclusion, HFP might increase intestinal fluid secretion by promoting Cl⁻ secretion, which in turn advanced mucus hydration as well as regulated gut microbiota to improve intestinal health. Therefore, H. caput-medusae (Bull. Fr.) Pers. could be potentially used in the regulation of intestinal secretion and microbes.

Assessment of adaptive immune responses of dairy cows with Burkholderia contaminans-induced mastitis

Burkholderia contaminans, an emerging pathogen related to cystic fibrosis, is known to cause potentially fatal infections in humans and ruminants, especially in immunocompromised individuals. However, the immune responses in cows following its infection have not been fully elucidated. In this study, T- and B-lymphocytes-mediated immune responses were evaluated in 15 B. contaminans-induced mastitis cows and 15 healthy cows with multi-parameter flow cytometry. The results showed that infection with B. contaminans was associated with a significant decrease in the number and percentage of B lymphocytes but with a significant increase in the proportion of IgG⁺CD27⁺ B lymphocytes. This indicated that humoral immune response may not be adequate to fight intracellular infection, which could contribute to the persistent bacterial infection. In addition, B. contaminans infection induced significant increase of γδ T cells and double positive (DP) CD4⁺CD8⁺ T cells but not CD4⁺ or CD8⁺ (single positive) T cells in blood. Phenotypic analysis showed that the percentages of activated WC1⁺ γδ T cells in peripheral blood were increased in the B. contaminans infected cows. Interestingly, intracellular cytokine staining showed that cattle naturally infected with B. contaminans exhibited multifunctional TNF-α⁺IFN-γ⁺IL-2⁺ B. contaminans-specific DP T cells. Our results, for the first time, revealed a potential role of IgG⁺CD27⁺ B cells, CD4⁺CD8⁺ T cells and WC1⁺ γδ T cells in the defense of B. contaminans-induced mastitis in cows.

Microbiome-Metabolomics Insights into the Milk of Lactating Dairy Cows to Reveal the Health-Promoting Effects of Dietary Citrus Peel Extracts on the Mammary Metabolism

The effects of dietary supplementation with citrus peel extract (CPE) on milk biochemical parameters, milk bacterial community, and milk metabolites were evaluated. Eight lactating cows were allocated to a replicated 4 × 4 Latin square. Experimental treatments included the control diet (CON), and CON supplemented with CPE at 50 g/d (CPE50), 100 g/d (CPE100), and 150 g/d (CPE150). Supplementing with CPE linearly decreased milk interleukin-6 and malondialdehyde concentrations and linearly increased lysozyme activity and 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity. Compared with CON, the milk of CPE150 cows had fewer abundances of several opportunistic pathogens and psychrotrophic bacteria, such as Escherichia-Shigella, Sphingobacterium, Alcaligenes, Stenotrophomonas, and Ochrobactrum. Supplementing with CPE significantly altered the metabolic profiling in the milk. The metabolites of flavonoids were enriched in the milk of cows fed CPE150, while some proinflammation compounds were decreased compared with CON. Correlation analysis showed that the change in the bacterial community might partly contribute to the alteration in the expression of milk cytokines. In conclusion, CPE exerts health-promoting effects (e.g., antioxidant, anti-microbial, and anti-inflammatory) in the mammary metabolism of cows due to its flavonoid compounds, which also provide additional value in terms of milk quality improvement.

Testing Two Somatic Cell Count Cutoff Values for Bovine Subclinical Mastitis Detection Based on Milk Microbiota and Peripheral Blood Leukocyte Transcriptome Profile

Somatic cell count (SCC) is an important indicator of the health state of bovine udders. However, the exact cut-off value used for differentiating the cows with healthy quarters from the cows with subclinical mastitis remains controversial. Here, we collected composite milk (milk from four udder quarters) and peripheral blood samples from individual cows in two different dairy farms and used 16S rRNA gene sequencing combined with RNA-seq to explore the differences in the milk microbial composition and transcriptome of cows with three different SCC levels (LSCC: <100,000 cells/mL, MSCC: 100,000−200,000 cells/mL, HSCC: >200,000 cells/mL). Results showed that the milk microbial profiles and gene expression profiles of samples derived from cows in the MSCC group were indeed relatively easily discriminated from those from cows in the LSCC group. Discriminative analysis also uncovered some differentially abundant microbiota at the genus level, such as Bifidobacterium and Lachnospiraceae_AC2044_group, which were more abundant in milk samples from cows with SCC below 100,000 cells/mL. As for the transcriptome profiling, 79 differentially expressed genes (DEGs) were found to have the same direction of regulation in two sites, and functional analyses also showed that biological processes involved in inflammatory responses were more active in MSCC and HSCC cows. Overall, these results showed a similarity between the milk microbiota and gene expression profiles of MSCC and HSCC cows, which presented further evidence that 100,000 cells/ml is a more optimal cut-off value than 200,000 cells/mL for intramammary infection detection at the cow level.