NE1048: Mastitis Resistance to Enhance Dairy Food Safety
Statement of Issues and Justification
In the United States, cash receipts from marketing of milk during 2010 totaled $31.4 billion (NASS, 2011) and it is estimated that U.S. consumers spend approximately 11% of their food dollars on dairy products (IDFA 2009). However, the dairy industry continues to experience significant monetary drain through the losses associated with common diseases. Bovine mastitis is the most costly infectious disease currently affecting dairy cattle. Recent estimates suggest that economic losses due to clinical and subclinical mastitis are in the range of $200 per cow per year (Hogeveen et al., 2011). These losses are primarily due to lost milk production, increased veterinary costs, increased cow mortality, and discarded milk. While significant advances have been made in controlling some types of mastitis, the complex etiology of the disease and ongoing changes in dairy practices dictate that new and more effective methods for control and treatment be developed over time. Single site studies are often limited in terms of expertise and cattle numbers. A multi-state project provides advantages in terms of increased numbers of herds and cattle as well as multiple levels of expertise.The purpose of NE-1028 is to coordinate multidisciplinary research efforts on mastitis that are being conducted at various laboratories throughout the United States. The magnitude and scope of attempting to solve these problems extend far beyond the ability of any one institution. The ability to cooperate on a regional and national basis allows the integration of resources and knowledge to address this problem. Recognition of the need for a coordinated effort to study resistance of the dairy cow to mastitis resulted in the design and initiation of multi-State Project NE-1028. The NE-1028 project has provided a forum for new and established researchers to develop collaborative relationships, and to share resources and expertise. The NE-1028 project is comprised of three objectives 1) characterization of host mechanisms associated with mastitis susceptibility and resistance, 2) characterization and manipulation of virulence factors of mastitis pathogens for enhancing host defenses, and 3) assessment and application of new technologies that advance mastitis control, milk quality, and dairy food safety. Accomplishments in the last 5 years are listed below by objective.
Objective 1: Characterization of host mechanisms associated with mastitis susceptibility and resistance.
Achievements include determination of antibody response following vaccination against Staphylococcus aureus, as well as Escherichia coli; understanding the risk for E. coli mastitis during a S. aureus infection; evaluation of neutrophil function in the peripartum period and during vitamin E supplementation; determination of the relationship between feeding behavior, animal activity and intramammary infection; understanding the host response during challenge with Enterococcus faecium; determination of the role of lactoferrin in Streptococcus uberis internalization by epithelial cells and the role of dietary phosphorus in immune function; evaluation of the role of superantigens in the differentiation of monocytes into dendritic cells; determination of the effect of lipoxygenase metabolites on platelet activating factor in E. coli mastitis; evaluation of the role of CXCR1 in mastitis susceptibility and host binding in S. uberis infections; discovery of associations between genetic susceptibility to mastitis and altered actin expression in neutrophils; an evaluation of the factors associated with cytokine levels and acute phase proteins; evaluation of the relationships between the metabolic dynamics of fat mobilization (especially during the periparturient period) and immune responses focusing on the impact of fat mobilization on oxidative stress and the ensuing impact on mononuclear cell membrane lipids/inflammatory responses; and determination of association between hepatic retinol binding protein and key pro-inflammatory markers in dairy cows.
Objective 2: Characterization and manipulation of virulence factors of mastitis pathogens for enhancing host defenses.
A major achievement for this objective is the continued examination of the role of coagulase-negative staphylococci on mastitis. More detailed examination of this diverse group of bacteria, including genotypic identification, has revealed that different species have surprisingly different effects on pathogenesis. Some species cause little or no decline in milk production. Additional progress is being made on using PCR-based techniques to identify pathogens in high SCC milk that had previously been declared as no growth using traditional culture techniques. This will be of great, widespread importance in mastitis treatment and research. Continued work exploring the development of bacterial resistance to commonly used antimicrobials is providing needed information on this critical treatment of mastitis. Antimicrobial resistance patterns of bovine and human isolates appear similar, and recent work suggests that mastitis therapeutics do not seem to induce or select for resistant bacteria (Barlow, 2011). Additional achievements include further identification of pathogen virulence factors and their association with mastitis pathogenesis, and detailed in vitro studies on bacterial adherence to, and penetration into mammary epithelial cells.
Objective 3: Assessment and application of new technologies that advance mastitis control, milk quality, and dairy food safety.
Achievements include evaluation of S. aureus and E. coli mastitis vaccines; development and application of milk residue testing; development of control programs for S. aureus and Mycoplasma spp.; evaluation of extended therapy for S. aureus and S. uberis mastitis and assessment of methods for on-farm and laboratory diagnosis of mastitis and food-borne pathogens. Improvements in diagnostic technologies include development and application of PCR to detect Mycoplasma mastitis; to identify and speciate pathogenic Prototheca (algae) as a screening technique for bulk tank filters; and to validate 16S gene sequence analysis for mastitis pathogen detection. These molecular techniques are critically important tools in mastitis treatment. Other achievements include developing and assessing techniques for evaluating milk quality in sheep and goats; and evaluation of an in-line milk analysis system for somatic cell count and other quality assessment components; and studies of colostral quality assessment methods. Finally, several workers have reported on alternative methods of preventing (probiotic) and treating (botanical/novel intramammary infusions) mastitis.
In addition, the group has completed portions and has work in progress on several other collaborative studies which include determination of antibiotic residues in heifers treated with intramammary antibiotics before parturition (coordinated by CT), understanding virulence factors and host adaptation to Klebsiella spp. (NY, VA, Moredun), evaluation of environmental streptococcal mastitis (IA, IL, TN, WA, VA), evaluation of the role of vaccination in mastitis prevention (GA, MI, MO), evaluation of genetic selection for milk production on innate immune response (VT and MN), and the standardization of definitions for intramammary infection (PEI, ONT). Through the concerted and collaborative efforts of its member stations, the NE- 1028 has met the milestones detailed in the project description and will continue to work on similar collaborative projects in the next 5 years.
Data generated under the auspices of the NE-1028 project have been used by member stations to gain intramural and extramural funding for mastitis research. In addition, a subcommittee of NE-1028 submitted a proposal for the USDA Coordinated Agricultural Project (CAP) program in July 2010. Although the proposal was not funded, the group members are eager to re-submit for related requests for proposals. As a multi-State, multi-institution project, the NE- 1028 is uniquely situated to apply for CAP funding should mastitis and milk quality become a targeted area of research.
The mastitis research workers group has met in conjunction with the NE-1028 annual meeting for many years, and in recent years, the mastitis research workers topics have been included in NE-1028 minutes, showing current active areas of research by NE-1028 members. International visitors and collaborators are often included in these presentations. In addition to the mastitis research workers conference, the NE-1028 members provide technology transfer to the scientific community and industry stakeholders. In the last 4 years, members of the project have collectively published multiple book chapters, in excess of 192 peer-reviewed journal articles, over 300 abstracts and proceedings, and presented numerous oral and poster presentations related to mastitis, milk quality, and food safety. Venues for oral and poster presentations have included the National Mastitis Council regional and annual meetings (attendees include researchers, veterinarians, dairy producers, and representatives from industry), Conference for Research Workers in Animal Diseases, American Association of Bovine Practitioners annual meetings, International Dairy Federation meetings, American Dairy Science Association meetings, World Buiatrics Congress meetings, American Society of Microbiology meetings, Conference on Production Diseases in Farm Animals, Plant and Animal Genome Conference, Agriculture and Agri-Food Canada - Food Safety meetings, American College of Veterinary Internal Medicine annual forum meetings, and several regional extension and veterinary continuing education meetings.
The continuation of the NE-1028 multistate project is of utmost importance to foster research in mastitis leading to the provision of science based information to dairy producers and the dairy industry. The impact of the European Union's strict enforcement of import regulations on milk quality highlights the need to continue efforts to reduce the incidence of mastitis. These new regulations require milk export companies to certify that any farm contributing milk must show a bulk milk cell count below 400,000 cells/mL. This regulation has recently been supported by the National Mastitis Council as a goal for all US dairies. Mechanisms leading to improvement in milk quality, dairy animal welfare, and appropriate use of antimicrobial therapeutics form the basis of research conducted in the NE-1028 multistate project. Given that approximately 25% of US bulk milk shipments exceeded 400,000 cells/mL in 2010, it is clear that continued mastitis research and education are required to maintain the global competitiveness of the US dairy industry (USDA APHIS, 2011).
Furthermore, the animal agriculture industry in general is under closer scrutiny than ever before by various interest groups. The work of the NE-1028 is clearly focused on reducing mastitis, the most significant animal health issue in the dairy industry. In summary, the NE-1028 project is a productive group of collaborators that has provided new and meaningful information to all levels of the dairy industry from the bench scientist to the dairy producer with regard to bovine mastitis control, treatment and prevention. In the next 5 years we will continue to pursue collaborative projects under our 3 stated objectives which will lead to new information of value to the management of dairy cattle mastitis. Mastitis is an evolving disease syndrome, as is the science that studies mastitis; therefore, continued research efforts are needed.
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