NE1028: Mastitis Resistance to Enhance Dairy Food Safety
Statement of Issues and JustificationBovine mastitis is the most costly infectious disease currently affecting dairy cattle. 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.
In the United States, the dairy industry contributes in excess of 65 billion dollars per year to the national economy, and provides jobs for over 1 million Americans. The single most costly disease of dairy cattle and a major monetary drain on the dairy industry is bovine mastitis. Mastitis is defined as an inflammation of the mammary gland that is almost always associated with bacterial infection. Mastitis affects every dairy farm and approximately 38% of dairy cows in the United States. The National Mastitis Council estimates that this devastating disease complex costs the dairy industry more than 2 billion dollars per year or approximately $180.00 per cow. These losses are primarily due to lost milk production, increased veterinary costs, increased cow mortality, and discarded milk.
The purpose of the Multi-State Mastitis Research Project (MMRP; formerly designated NE-112 and most recently designated NE-1009) 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 the MMRP. The MMRP has provided a forum for new and established researchers to develop collaborative relationships, and to share resources and expertise.
In the past several years, we have initiated joint projects, which were conceived, developed, and run under the auspices of the MMRP. Examples of these projects and linkages between stations include completion of 2 multi-State projects evaluating prepartum intramammary antibiotic treatment of heifers on the prevalence of early lactation mastitis and first lactation performance parameters (Summarized below). In addition, the group has completed portions and has work in progress on several other collaborative studies which include evaluation of duplicate versus single samples for the diagnosis of intramammary infection (coordinated by ONT), determination of antibiotic residues in heifers treated with intramammary antibiotics before parturition (coordinated by CT), evaluation of cow and mammary quarter level risk factors at dry-off for the development of mastitis during the dry period (IA, NY, ONT, PEI), evaluation of external teat sealants during the dry period (IA, ONT, PEI), evaluation of environmental streptococcal mastitis (IA, IL, WA, VA), and evaluation of on-farm culture technologies and their use in making treatment decisions for clinical and subclinical mastitis (IA, MN, ONT, PEI, WI). Through the concerted and collaborative efforts of its members, the MMRP has been highly productive and will continue to work on similar collaborative projects in the next 5-years.
Examples of Completed Multi-State Projects: Heifer Prepartum Treatment Trials
Research data accumulated over the past 20 years suggest that a high proportion of dairy heifers develop intramammary infections (IMIs) prior to calving. Because of the high prevalence of prepartum IMIs in heifers, several single institution studies have evaluated prepartum treatment of heifers to decrease the prevalence of IMI and one such study has evaluated the economic viability of such treatment by measuring first lactation performance parameters. However, large multi-site studies were lacking. Hence, during the last 5 years members of the MMRP have undertaken two collaborative multi-State studies to evaluate the effect of prepartum treatment of dairy heifers on first lactation udder health and performance. Study 1 (Middleton et al., 2005) involved two centers in the MMRP (IA & MO) and Study 2 (Borm AA et al., 2006) involved 7 centers (WA, ONT, OH, CT, TN, NY, & LA). Study 1 included 183 dairy heifers on 2 farms and Study 2 included 561 heifers on 9 farms. Heifers were divided into treated and untreated control groups with treated heifers receiving a single intramammary dose of either pirlimycin (Study 1) or cephapirin (Study 2) in each mammary quarter approximately 10-21 days prior to parturition. Samples were collected before treatment and after calving for microbiologic assessment and post-calving production parameters were recorded and evaluated. Both studies found that the majority of prepartum IMIs were caused by coagulase negative staphylococci (CNS) and treated quarters had a significantly higher cure rate than untreated quarters. Treatment did not significantly affect milk production in either study; however, there was a significant treatment by herd interaction for milk production in Study 2. In Study 1, one herd realized a significant reduction in milk somatic cell count in treated quarters while no difference was detected between groups in the other herd. In Study 2, quarters cured of either a CNS or major mastitis pathogen IMI had a lower milk somatic cell count in the first 200 days of lactation. In addition, Study 2 found no significant effect of treatment on services per conception or days open. Given these results, use of prepartum intramammary antibiotic therapy in heifers as a universal strategy to increase first lactation performance may not be warranted. Results from these studies have led to new collaborative studies evaluating milk residue detection and test kit validation in treated heifers and studies to examine methods of speciating CNS and characterizing differences in pathogenicity between CNS species and genotypes.
Data generated under the auspices of the MMRP project has been used by member stations to gain intramural and extramural funding for mastitis research. While the majority of research conducted by the group is funded by intramural and extramural grants and corporate contracts awarded to individual participating stations, our Canadian colleagues and collaborators/participants in the MMRP were recently awarded a multi-year, multi-million dollar grant to fund the Canadian Bovine Mastitis Research Network. In addition, a subcommittee of MMRP members met in December 2003 and February 2004 to outline and discuss a proposal for the USDA Coordinated Agricultural Project (CAP) program. However, the 2004 and 2005 requests for proposals were in areas other than milk quality and food safety. As a multi-State, multi-institution project the MMRP is uniquely situated to apply for CAP funding should mastitis and milk quality become a targeted area of research. Examples of current jointly funded research are listed below.
1) Pathogenesis of chronic E. coli mastitis. Y.H. Schukken (NY) & S.P. Oliver (TN). New York Vitamin Settlement Grant
2) Diagnostics for coagulase negative staphylococci. P. Ruegg (WI) & R.N. Zadoks (NY). Formula Funds
3) On-farm culture and treatment protocols. R. Erskine (MI) & S. Wagner (ND). Mastitis Research Foundation
4) Mathematical and molecular epidemiology of mastitis. J. Bramley, J. Barlow (VT) & Y.H. Schukken, R.N. Zadoks (NY). USDA-NRI
5) Presence of mastitis pathogens in culture-negative milk samples from cows with clinical mastitis. H.W. Barkema, R. Olde Riekerink (CAN) & R. N. Zadoks (NY). Mastitis Research Foundation
6) On-farm mastitis diagnostics. S. Godden (MN) & K.E. Leslie (CAN) & P. Ruegg (WI). MN Ag Experiment Station
The mastitis research workers group has met in conjunction with the MMRP annual meeting for many years, and in recent years, the mastitis research workers topics have been included in MMRP minutes, showing current active areas of research by MMRP members. International visitors and collaborators are often included in these presentations. In addition to the mastitis research workers conference, the MMRP members provide technology transfer to the scientific and lay communities. In the last 5 years, members of the project have collectively published several book chapters, approximately 290 peer-reviewed journal articles, approximately 270 abstracts and proceedings, and presented numerous oral and poster presentations related to mastitis, milk quality, and food safety (Appendix 1: Publications 2002-2007). 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.
In summary, the MMRP 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 on 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 which studies mastitis and therefore continued research efforts are needed.
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