A Novel Lactobacilli-Based Teat Disinfectant for Improving Bacterial Communities in the Milks of Cow Teats with Subclinical Mastitis

Omonijo F, A Ganai N, M. Ibeagha-Awemu E, Mudasir Ahmad S. Immunotherapy in mastitis: state of knowledge, research gaps and way forward

Mastitis is an inflammatory condition that affects dairy cow's mammary glands. Traditional treatment approaches with antibiotics are increasingly leading to challenging scenarios such as antimicrobial resistance. In order to mitigate the unwanted side effects of antibiotics, alternative strategies such as those that harness the host immune system response, also known as immunotherapy, have been implemented. Immunotherapy approaches to treat bovine mastitis aims to enhance the cow's immune response against pathogens by promoting pathogen clearance, and facilitating tissue repair. Various studies have demonstrated the potential of immunotherapy for reducing the incidence, duration and severity of mastitis. Nevertheless, majority of reported therapies are lacking in specificity hampering their broad application to treat mastitis. Meanwhile, advancements in mastitis immunotherapy hold great promise for the dairy industry, with potential to provide effective and sustainable alternatives to traditional antibiotic-based approaches. This review synthesizes immunotherapy strategies, their current understanding and potential future perspectives. The future perspectives should focus on the development of precision immunotherapies tailored to address individual pathogens/group of pathogens, development of combination therapies to address antimicrobial resistance, and the integration of nano- and omics technologies. By addressing research gaps, the field of mastitis immunotherapy can make significant strides in the control, treatment and prevention of mastitis, ultimately benefiting both animal and human health/welfare, and environment health.

Assessment of Lactococcus Cremoris preparations for the pre- and post-milking teat disinfection

Good hygienic milking practices including the disinfection of the cow teat skin before and after milking aimed at preventing the occurrence of new intramammary infections (IMI) in dairy cows. This practice is generally performed using disinfectants, and in the current context of attention to the emergence of resistances, it is of greatest interest to evaluate alternative solutions that can expand treatment options. We assessed the efficacy of a pre-dipping and a post-dipping product based on the bacteriocin-containing culture of Lactococcus cremoris strain FT27, as compared to commercial disinfectants. FT27 was selected for the bactericidal activity in vitro against food pathogens. In the present study, it also revealed a high bactericidal activity against the main mastitis pathogens, most likely related to Nisin A production, according to genomic and proteomic analysis. The lactococcus-based preparations were applied in two commercial dairy farms in Northern Italy. Overall, 298 dairy cows were enrolled, 141 in the treated group (TR), and 157 in the control group (CTR). The cows were sampled at quarter level every two weeks for 3 months. During the trial, all cows showed a good health status. The hygiene level for udder, flanks and legs was generally good (on average < 3 score); the udder hygiene was significantly worse (P < 0.01) in the CTR group. The teat apex hyperkeratosis was overall low (on average < 2 score). We recorded no significant differences between the two experimental groups in the Somatic Cell Count (SCC) values and the bacteriological results. The overall frequency of new IMI was low, ranging 0.6 - 0.5% for S. aureus in the TR or CTR group respectively, to 2.6-4.4% for NASM. Regarding Str. spp., the new IMI accounted for 1.7% or 1.9% in the TR or CTR group, respectively. Notably, the incidence of S. aureus new IMI did not increase during the study, even though neither of the two herds segregated the positive cows. The non-inferiority test showed that the Lactococcus-based pre- and post-dipping products had an efficacy comparable to proven commercial disinfectants in maintaining udder health and preventing new IMI, thus representing a possible alternative to current teat dip products.

Molecular characteristics and antimicrobial susceptibility profiles of bovine mastitis agents in western Türkiye

IMPORTANCE

Identifying bovine mastitis agents using molecular methods to reveal their phylogenetic relationships and antimicrobial resistance profiles is essential for developing up-to-date databases in mastitis cases that cause severe economic losses.

OBJECTIVE

This study examined bacterial mastitis agents in cows with clinical and subclinical mastitis observed in various dairy cattle farms to reveal their phylogenetic relationships and antibiotic resistance properties.

METHODS

Sixty-two clinical and subclinical bovine mastitis milk samples were collected from 15 dairy farms. The polymerase chain reaction (PCR) was used to amplify the 16S rRNA gene regions of the bacteria. The 16S rRNA gene sequences obtained from sequencing include the V4-V6 regions. The strains were compared using a similarity analysis method that produced phylogenetic trees using the Molecular Evolutionary Genetics Analysis 11 program. Antibiotic susceptibilities were determined using the Kirby-Bauer disk diffusion method.

RESULTS

Sixty-three bacteria were isolated and identified in this study. The most isolated bacteria from all mastitis cases were Staphylococcus spp. (30.2%), Escherichia coli (25.4%), Streptococcus spp. (14.3%), and Aerococcus spp. (7.9%), respectively. The phylogenetic trees were drawn from the 16S rRNA sequences. Some of these bacteria showed resistance to different types of antibiotics at varying rates.

CONCLUSIONS AND RELEVANCE

The bacteria isolated in this study originated from environmental sources. Regular cleaning of barns and proper hygiene practices are essential. Regular screenings for mastitis should be conducted in herds instead of the random or empirical use of antibiotics.

Invited review: "Probiotic" approaches to improving dairy production: Reassessing "magic foo-foo dust"

The gastrointestinal microbial consortium in dairy cattle is critical to determining the energetic status of the dairy cow from birth through her final lactation. The ruminant's microbial community can degrade a wide variety of feedstuffs, which can affect growth, as well as production rate and efficiency on the farm, but can also affect food safety, animal health, and environmental impacts of dairy production. Gut microbial diversity and density are powerful tools that can be harnessed to benefit both producers and consumers. The incentives in the United States to develop Alternatives to Antibiotics for use in food-animal production have been largely driven by the Veterinary Feed Directive and have led to an increased use of probiotic approaches to alter the gastrointestinal microbial community composition, resulting in improved heifer growth, milk production and efficiency, and animal health. However, the efficacy of direct-fed microbials or probiotics in dairy cattle has been highly variable due to specific microbial ecological factors within the host gut and its native microflora. Interactions (both synergistic and antagonistic) between the microbial ecosystem and the host animal physiology (including epithelial cells, immune system, hormones, enzyme activities, and epigenetics) are critical to understanding why some probiotics work but others do not. Increasing availability of next-generation sequencing approaches provides novel insights into how probiotic approaches change the microbial community composition in the gut that can potentially affect animal health (e.g., diarrhea or scours, gut integrity, foodborne pathogens), as well as animal performance (e.g., growth, reproduction, productivity) and fermentation parameters (e.g., pH, short-chain fatty acids, methane production, and microbial profiles) of cattle. However, it remains clear that all direct-fed microbials are not created equal and their efficacy remains highly variable and dependent on stage of production and farm environment. Collectively, data have demonstrated that probiotic effects are not limited to the simple mechanisms that have been traditionally hypothesized, but instead are part of a complex cascade of microbial ecological and host animal physiological effects that ultimately impact dairy production and profitability.

Evaluation of the Efficacy of a Lactobacilli-Based Teat Detergents for the Microbiota of Cows Teats Using an Untargeted Metabolomics Approach

Teat cleaning pre- and post-milking is important for the overall health and hygiene of dairy cows. The purpose of this research was to evaluate the effectiveness of a teat detergents based on lactic acid bacteria according to changes in somatic cell count and cow-milk metabolites. Sixty-nine raw milk samples were collected from 11 Holstein-Friesian cows in China during 12 days of teat cleaning. An ultra-performance liquid chromatography-quadrupole-time of flight mass spectrometry-based untargeted metabolomic approach was applied to detect metabolomic differences after treatment with lactic acid bacteria and chemical teat detergents in cows with subclinical mastitis. The results suggest that the lactobacilli-based teat detergents could reduce somatic cell count and improve microhabitat of cow teat apex by adjusting the composition of metabolites. Furthermore, the somatic cell count could be decreased significantly within 10 days following the cleaning protocol. Lactic acid bacteria have the potential to be applied as a substitution to teat chemical detergents before and after milking for maintenance of healthy teats and breasts. Further, larger scale validation work is required to support the findings of the current study.

Efficiency of probiotic culture consortium application for disinfection of dairy farm premises and prevention of mastitis in cows

Objective

In this work, the effect of probiotics on the state of the microbial background of the livestock building, on the state of udder teats, and on the prevalence of latent mastitis was investigated. Long-term use of the consortium has bactericidal activity against all cultures studied, especially the causative agent of mastitis, Staphylococcus aureus, except Proteus mirabilis, Proteus vulgaris, and Escherichia coli.

Materials and Methods

The washes from animal housings and milk samples were collected from the dairy farms "Astana-Onim" Joint Stock Company and "Rodina" Limited Liability Partnership (Kazakhstan). The cleaning solutions and probiotic agents were applied directly to the udder teats of cows before and after milking. Diagnosis of subclinical mastitis was performed using the Kenotest rapid mastitis test. Directly counting the number of somatic cells in the collected milk samples from each cow was performed on a somatic cell counter.

Results

Pathogenic microorganisms, including S. aureus bacteria (50% of samples) and bacteria of the E. coli group, Enterobacter aerogenes, and P. mirabilis (36% of samples), were detected on the udder skin and milk wipes. Using a consortium of probiotic microorganisms positively affects the mammary gland more quickly than using mastitis prevention agents alone. Probiotic use for a month resulted in a significant improvement in udder teat condition, with 60.7% of teats showing normal physiological reaction to milking, a decrease in complicated hyperkeratosis, and an increase in uncomplicated mastitis. The studies showed that in the experimental group, there was a 1.5-fold reduction in the number of cows with clinically pronounced mastitis. The experimental group showed no significant changes in the number of animals with high somatic cell levels before and after the study, while the control group without probiotics had a significant increase in diseased animals after 1 month.

Conclusion

The use of a probiotic consortium has shown promising results in reducing the incidence of mastitis and improving milk quality in cows.

The use of teat disinfectants and milking machine cleaning products in commercial Holstein-Friesian farms

The aim of our study was to survey and analyze the use of pre- and post-milking teat disinfectants and milking machine cleaning products in large commercial Holstein-Friesian farms. A total of 43 Hungarian dairy farms with 31,430 cows with an average herd size of 731 cows were surveyed in 2014 by using a questionnaire via personal interviews. In the statistical analysis, we used ANOVA models and Tukey's multiple comparison method. Furthermore, seven in-depth individual interviews were conducted with farm managers. The results showed that 83.7% of the farms used different pre-milking disinfection methods (65.1% teat dips) and all of them applied post-milking disinfection. In the herds, chlorhexidine (42.9%) and other chlorine (21.4%) compounds were the most widely used active ingredients in the pre-milking disinfection, while iodine in the post-milking disinfection (53.8%). Lactic acid was ranked second in both disinfections (25.0 vs. 41.0%). In post-milking teat disinfection, the use of iodine and lactic acid combined with other active ingredients showed a significant relationship with SCC (p = 0.0454; p = 0.0113). In the milking machine cleaning process, the most frequently used active ingredients were sodium hypochlorite (80.0%) and sodium hydroxide (60.0%) as caustic detergents, while phosphoric acid (81.3%) as an acidic product. A significant relationship was found between the use of phosphoric acid combined with nitric acid, and the use of a combination of phosphoric acid, nitric acid, and organic acid and SCC (p = 0.0483; p = 0.0477). For farm decision-makers, the most decisive factor in the procurement of teat disinfectants was the active ingredient (3.4 on a scale of 1 to 10 where 1 was the most important), while regarding milking machine cleaning products the price (3.2).

Research progress on the association between mastitis and gastrointestinal microbes in dairy cows and the effect of probiotics

Mastitis in dairy cows affects milk quality and thereby constrains the development of the dairy industry. A clear understanding of the pathogenesis of mastitis can help its treatment. Mastitis is caused by the invasion of pathogenic bacteria into the mammary gland through the mammary ducts. However, recent studies suggested that an endogenous entero-mammary pathway in dairy cattle might also be playing an important role in regulating mastitis. Also, probiotic intervention regulating host gut microbes has become an interesting tool to control mastitis. This review discusses the association of gastrointestinal microbes with mastitis and the mechanism of action of probiotics in dairy cows to provide new ideas for the management of mastitis in large-scale dairy farms.

Characterization of rumen, fecal, and milk microbiota in lactating dairy cows

Targeting the gastrointestinal microbiome for improvement of feed efficiency and reduction of production costs is a potential promising strategy. However little progress has been made in manipulation of the gut microbiomes in dairy cattle to improve milk yield and milk quality. Even less understood is the milk microbiome. Understanding the milk microbiome may provide insight into how the microbiota correlate with milk yield and milk quality. The objective of this study was to characterize similarities between rumen, fecal, and milk microbiota simultaneously, and to investigate associations between microbiota, milk somatic cell count (SCC), and milk yield. A total of 51 mid-lactation, multiparous Holstein dairy cattle were chosen for sampling of ruminal, fecal, and milk contents that were processed for microbial DNA extraction and sequencing. Cows were categorized based on low, medium, and high SCC; as well as low, medium, and high milk yield. Beta diversity indicated that ruminal, fecal, and milk populations were distinct (p &lt; 0.001). Additionally, the Shannon index demonstrated that ruminal microbial populations were more diverse (p &lt; 0.05) than were fecal and milk populations, and milk microbiota was the least diverse of all sample types (p &lt; 0.001). While diversity indices were not linked (p &gt; 0.1) with milk yield, milk microbial populations from cows with low SCC demonstrated a more evenly distributed microbiome in comparison to cows with high SCC values (p = 0.053). These data demonstrate the complexity of host microbiomes both in the gut and mammary gland. Further, we conclude that there is a significant relationship between mammary health (i.e., SCC) and the milk microbiome. Whether this microbiome could be utilized in efforts to protect the mammary gland remains unclear, but should be explored in future studies.

Commensal Bacillus subtilis from cow milk inhibits Staphylococcus aureus biofilm formation and mastitis in mice

The colonization and virulence production of Staphylococcus aureus (S. aureus), a known pathogen that induces mastitis, depend on its quorum-sensing (QS) system and biofilm formation. It has been reported that Bacillus can inhibit the QS system of S. aureus, thereby reducing S. aureus colonization in the intestine. However, whether Bacillus affects S. aureus biofilm formation and consequent colonization during mastitis is still unknown. In this study, the differences in the colonization of S. aureus and Bacillus were first analyzed by isolating and culturing bacteria from milk samples. It was found that the colonization of Bacillus and S. aureus in cow mammary glands was negatively correlated. Secondly, we found that although Bacillus did not affect S. aureus growth, it inhibited the biofilm formation of S. aureus by interfering its QS signaling. The most significant anti-biofilm effect was found in Bacillus subtilis H28 (B. subtilis H28). Finally, we found that B. subtilis H28 treatment alleviated S. aureus-induced mastitis in a mice model. Our results rerealed that bovine milk derived commensal Bacillus inhibited S. aureus colonization and alleviated S. aureus-induced mastitis by influencing biofilm formation, suggesting a potential targeted strategy to limit the colonization of S. aureus in vivo.

Influence of Post-Milking Treatment on Microbial Diversity on the Cow Teat Skin and in Milk

In dairy cattle, teat disinfection at the end of milking is commonly applied to limit colonization of the milk by pathogenic microorganisms via the teat canal. The post-milking products used can irritate the teat skin and unbalance its microbial population. Our study aimed to assess the impact of different milking products on the balance of the microbial communities on the teat skin of cows and in their milk. For 12 weeks at the end of each milking operation, three groups of seven Holstein dairy cows on pasture received either a chlorhexidine gluconate-based product (G) or a hydrocolloidal water-in-oil emulsion (A), or no post-milking product (C). The composition of the bacterial and fungal communities on the teat skin and in the milk were characterized using a culture-dependent method and by high-throughput sequencing of marker genes to obtain amplicon sequence variants (ASVs). The individual microbiota on the cows’ teat skin was compared for the first time to that of a cow pool. In contrast to the milk, the post-milking treatment influenced the microbiota of the teat skin, which revealed a high microbial diversity. The water-in-oil emulsion appeared to slightly favour lactic acid bacteria and yeasts and to limit the development of undesirable bacteria such as Pseudomonas and Staphylococcus.

PacBio sequencing revealed variation in the microbiota diversity, species richness and composition between milk collected from healthy and mastitis cows

Mastitis is the economically most important disease of dairy cows. This study used PacBio single-molecule real-time sequencing technology to sequence the full-length 16S rRNAs from 27 milk samples (18 from mastitis and nine from healthy cows; the cows were at different stages of lactation). We observed that healthy or late stage milk microbiota had significantly higher microbial diversity and richness. The community composition of the microbiota of different groups also varied greatly. The healthy cow milk microbiota was predominantly comprised of Lactococcus lactis, Acinetobacter johnsonii, and Bacteroides dorei, while the milk from mastitis cows was predominantly comprised of Bacillus cereus. The prevalence of L. lactis and B. cereus in the milk samples was confirmed by digital droplets PCR. Differences in the milk microbiota diversity and composition could suggest an important role for some these microbes in protecting the host from mastitis while others associated with mastitis. The results of our research serve as useful references for designing strategies to prevent and treat mastitis.

Advances in therapeutic and managemental approaches of bovine mastitis: a comprehensive review

Mastitis (intramammary inflammation) caused by infectious pathogens is still considered a devastating condition of dairy animals affecting animal welfare as well as economically incurring huge losses to the dairy industry by means of decreased production performance and increased culling rates. Bovine mastitis is the inflammation of the mammary glands/udder of bovines, caused by bacterial pathogens, in most cases. Routine diagnosis is based on clinical and subclinical forms of the disease. This underlines the significance of early and rapid identification/detection of etiological agents at the farm level, for which several diagnostic techniques have been developed. Therapeutic regimens such as antibiotics, immunotherapy, bacteriocins, bacteriophages, antimicrobial peptides, probiotics, stem cell therapy, native secretory factors, nutritional, dry cow and lactation therapy, genetic selection, herbs, and nanoparticle technology-based therapy have been evaluated for their efficacy in the treatment of mastitis. Even though several strategies have been developed over the years for the purpose of managing both clinical and subclinical forms of mastitis, all of them lacked the efficacy to eliminate the associated etiological agent when used as a monotherapy. Further, research has to be directed towards the development of new therapeutic agents/techniques that can both replace conventional techniques and also solve the problem of emerging antibiotic resistance. The objective of the present review is to describe the etiological agents, pathogenesis, and diagnosis in brief along with an extensive discussion on the advances in the treatment and management of mastitis, which would help safeguard the health of dairy animals.

Bovine mastitis prevention and control in the post-antibiotic era

Mastitis is the most important disease in the dairy industry. Antibiotics are considered to be the first choice in the treatment of the disease. However, the problem of antibiotic residue and antimicrobial resistance, in addition to the impact of antibiotic abuse on public health, leads to many restrictions on uncontrolled antibiotic therapy in the dairy sector worldwide. Researchers have investigated novel therapeutic approaches to replace the use of antibiotics in mastitis control. These efforts, supported by the revolutionary development of nanotechnology, stem cell assays, molecular biological tools, and genomics, enabled the development of new approaches for mastitis-treatment and control. The present review discusses recent concepts to control mastitis such as breeding of mastitis-resistant dairy cows, the development of novel diagnostic and therapeutic tools, the application of communication technology as an educational and epidemiological tool, application of modern mastitis vaccines, cow drying protocols, teat disinfection, housing, and nutrition. These include the application of nanotechnology, stem cell technology, photodynamic and laser therapy or the use of traditional herbal medical plants, nutraceuticals, antibacterial peptides, bacteriocins, antibodies therapy, bacteriophages, phage lysins, and probiotics as alternatives to antibiotics.

Overview of the Potential Impacts of Climate Change on the Microbial Safety of the Dairy Industry

Climate change is expected to affect many different sectors across the food supply chain. The current review paper presents an overview of the effects of climate change on the microbial safety of the dairy supply chain and suggest potential mitigation strategies to limit the impact. Raw milk, the common raw material of dairy products, is vulnerable to climate change, influenced by changes in average temperature and amount of precipitation. This would induce changes in the microbial profile and heat stress in lactating cows, increasing susceptibility to microbial infection and higher levels of microbial contamination. Moreover, climate change affects the entire dairy supply chain and necessitates adaptation of all the current food safety management programs. In particular, the review of current prerequisite programs might be needed as well as revisiting the current microbial specifications of the receiving dairy products and the introduction of new pretreatments with stringent processing regimes. The effects on microbial changes during distribution and consumer handling also would need to be quantified through the use of predictive models. The development of Quantitative Microbial Risk Assessment (QMRA) models, considering the whole farm-to-fork chain to evaluate risk mitigation strategies, will be a key step to prioritize actions towards a climate change-resilient dairy industry.

Efficacy of a Lactobacillus-Based Teat Spray on Udder Health in Lactating Dairy Cows

Teat disinfection is a common pre- and post-milking mastitis prevention practice that is part of a mastitis control program in dairy herds. Commercially available teat disinfectants are generally chemical-based products. The use of these products has occasionally raised concerns about the risk of chemical residues in milk. An alternative treatment or prevention strategy based on probiotics has the potential to circumvent this risk. Two treatments were compared in a cross-over clinical trial in a single herd: a lactobacillus-based, post-milking teat spray (LACT), and a commercial iodine-based post-milking teat disinfectant product as (positive control, PC). The effect of the two treatments on cow somatic cell counts was quantified using a multivariate mixed-effects linear regression model with cow fitted as a random effect. The odds of teat end scores increasing from a low to a high score tended to be lower (OR = 0.74, 95% CI 0.54-1.01, P = 0.06) for cows receiving LACT treatment. On average, there was also a tendency for a lower somatic cell counts in the LACT treated cows (antilog of coefficient = 0.91, 95% CI 0.80-1.03, P = 0.13) compared with the PC treated cows. The application of the lactobacillus-based product to teats could reduce the rate of teat end scores progression from low to higher scores, and potentially improve teat end sphincter functions and udder health. Further, larger scale validation work is required to support the findings of the current study.

Bacteria Associated with Granulomatous Lobular Mastitis and the Potential for Personalized Therapy

Granulomatous lobular mastitis (GLM), also known as idiopathic granulomatous mastitis (IGM), is a chronic inflammatory lesion of the breast. The incidence of GLM has been increasing in recent years, especially among young women. The etiologies of GLM have not been fully elucidated but are associated with autoimmunity and bacterial infection. Bacteria, especially Corynebacterium species, play important roles in GLM. In this article, we review research progress regarding the bacteriology of GLM attained with the application of several new high-throughput detection techniques. Accurate detection might be important for deepening our understanding of the pathogenesis of GLM and hold promise for personalized GLM therapy.

Myricetin relieves LPS-induced mastitis by inhibiting inflammatory response and repairing the blood-milk barrier

Mastitis, an inflammation of mammary gland, is a serious disease that affects the health of dairy cows around the world. Myricetin, a flavonoid from Bayberry, has been reported to suppress various inflammatory response. The aim of this study was to evaluate the effect of myricetin on lipopolysaccharide (LPS)-induced in vivo and in vitro mastitis model and clarify the underlying mechanism. In vivo experiments, myricetin attenuated the severity of inflammatory lesion and neutrophil infiltration. Moreover, myricetin pretreatment induced a significant decrease in the activity of myeloperoxidase (MPO) and the production of TNF-α, IL-6, and IL-1β triggered by LPS. Myricetin pretreatment could also increase the integrity of the blood-milk barrier and upregulate the tight junction proteins in LPS-induced mice mastitis. In vitro, myricetin inhibited LPS-induced inflammatory response in mice mammary epithelial cells (mMECs). In the further mechanism studies, we found that the anti-inflammatory effect of myricetin was mediated by inhibiting LPS-induced phosphorylation of AKT, IKK-α, IκB-α, and P65 in vivo and in vitro. Collectively, these data suggested that myricetin effectively ameliorated the inflammatory response by inhibiting the AKT/IKK/NF-κB signaling pathway and repairing the integrity of blood-milk barrier in LPS-induced mice mastitis.

Could probiotics be the panacea alternative to the use of antimicrobials in livestock diets?

Probiotics are most frequently derived from the natural microbiota of healthy animals. These bacteria and their metabolic products are viewed as nutritional tools for promoting animal health and productivity, disease prevention and therapy, and food safety in an era defined by increasingly widespread antimicrobial resistance in bacterial pathogens. In contemporary livestock production, antimicrobial usage is indispensable for animal welfare, and employed to enhance growth and feed efficiency. Given the importance of antimicrobials in both human and veterinary medicine, their effective replacement with direct-fed microbials or probiotics could help reduce antimicrobial use, perhaps restoring or extending the usefulness of these precious drugs against serious infections. Thus, probiotic research in livestock is rapidly evolving, aspiring to produce local and systemic health benefits on par with antimicrobials. Although many studies have clearly demonstrated the potential of probiotics to positively affect animal health and inhibit pathogens, experimental evidence suggests that probiotics' successes are modest, conditional, strain-dependent, and transient. Here, we explore current understanding, trends, and emerging applications of probiotic research and usage in major livestock species, and highlight successes in animal health and performance.

Targeting gut microbiota as a possible therapy for mastitis

Mastitis, a disease that affects both dairy herds and humans, is recognized as the most common source of losses in the dairy industry. Antibiotics have been used for years as the primary treatment for mastitis. However, abuse of antibiotics has led to the emergence of resistant strains and the presence of drug residues and has increased the difficulty of curing this disease. In addition, antibiotics kill most of the microbes that are present in the digestive tract, leading to imbalances in the gut microbiome and destruction of the ecosystem that is normally present in the gut. Gut microbiota play an important role in the host's health and could be considered the "second brain" of the body. In recent years, the gut microbiota and their metabolites, including lipopolysaccharide (LPS) and short-chain fatty acids (SCFAs), have been shown to participate in the development of mastitis. LPS is the main component of the cell walls of gram-negative bacteria. Overproduction of rumen-derived LPS injures the rumen epithelium, resulting in the entry of LPS into the blood and damaged liver function; once in the blood, it circulates into the mammary gland, increasing blood-barrier permeability and leading to mammary gland inflammation. SCFAs, which are produced by gut microbiota as fermentation products, have a protective effect on mammary gland inflammatory responses and help maintain the function of the blood-milk barrier. Recently, increasing attention has been focused on the use of probiotics as a promising alternative for the treatment of mastitis. This review summarizes the effects of the gut microbiome and its metabolites on mastitis as well as the current of probiotics in mastitis. This work may provide a valuable theoretical foundation for the development of fresh ideas for the prevention and treatment of mastitis.

A Critical Appraisal of Probiotics for Mastitis Control

The urge to reduce antimicrobials use in dairy farming has prompted a search for alternative solutions. As infections of the mammary gland is a major reason for antibiotic administration to dairy ruminants, mammary probiotics have recently been presented as a possible alternative for the treatment of mastitis. To assess the validity of this proposal, we performed a general appraisal of the knowledge related to probiotics for mammary health by examining their potential modes of action and assessing the compatibility of these mechanisms with the immunobiology of mammary gland infections. Then we analyzed the literature published on the subject, taking into account the preliminary in vitro experiments and the in vivo trials. Preliminary experiments aimed essentially at exploring in vitro the capacity of putative probiotics, mainly lactic acid bacteria (LABs), to interfere with mastitis-associated bacteria or to interact with mammary epithelial cells. A few studies used LABs selected on the basis of bacteriocin production or the capacity to adhere to epithelial cells to perform in vivo experiments. Intramammary infusion of LABs showed that LABs are pro-inflammatory for the mammary gland, inducing an intense influx of neutrophils into milk during lactation and at drying-off. Yet, their capacity to cure mastitis remains to be established. A few preliminary studies tackle the possibility of using probiotics to interfere with the teat apex microbiota or to prevent the colonization of the teat canal by pathogenic bacteria. From the analysis of the published literature, it appears that currently there is no sound scientific foundation for the use of probiotics to prevent or treat mastitis. We conclude that the prospects for oral probiotics are not promising for ruminants, those for intramammary probiotics should be considered with caution, but that teat apex probiotics deserve further research.