- Animal Products: dairy
- Animal Production: preventive practices, therapeutics
- Education and Training: extension, on-farm/ranch research
- Sustainable Communities: sustainability measures
The high incidence and treatment rate of mastitis, defined as inflammation or infection of the mammary gland, and its associated economic losses, denotes it as a disease of interest for development of protocols for prudent antimicrobial use on dairies. One such protocol developed and implemented by our group at a large dairy (3500 cows) compared outcomes of a pathogen-specific protocol to a 5 day blanket treatment protocol. The strategic method of treatment decreased milk withholding time by 3 days for those cows enrolled. There were no significant differences in days to clinical cure, milk yield, and linear scores post-event, nor additional odds of culling in the months following. If dairies with similar mastitis etiologies employ this protocol, >65% of mild to moderate cases will not be treated. Judicious use of antibiotics by dairy farmers in states such as NY, which have prominent contributions to milk products, can create positive impacts on sustainability by preventing the selection of resistant organisms, thereby increasing product efficacy. A team of 6 dairies and their respective veterinarians as well as local Quality Milk Production Services laboratories will investigate the application of the protocol on moderate-sized dairies using three-time-a-week milk sample pickup or on farm culture (OFC). Producer’s antimicrobial use pre- and post-study will be assessed through surveys and records. Economic analysis will be performed for each group of dairies. Measures of success will include producer’s perception of outcomes, analysis of specificity and sensitivity of OFC, and monitor of milk quality, quantity, and mastitis incidences.
Project objectives from proposal:
In order to investigate current antimicrobial use on the dairy, a verbal questionnaire will be developed and administered to 6 selected NY dairies (see below) to determine perception of each dairy’s current clinical mastitis treatment protocol. Questions will be centered on whether the producer believes that the treatment is successful, but will also involve ease of implementation, reasons for current protocol use, and costs associated with treatment. Antimicrobial usage will be quantified using current cost of antimicrobial products, current receipts from animal health companies, current employee wages and time spent treating, and discarded milk costs. Mastitis incidence and percent of chronic cases will be quantified using monthly computer records, which are maintained at each dairy. Average milk production and bulk tank somatic cell count can also be obtained from DHIA records.
Clinical mastitis cases will be assessed for inclusion at 6 moderate-sized dairies (500-1000 cows) in New York. Dairies will be chosen due to size, a monthly incidence of 5-6% CM, availability of reliable health records, consultation opportunity with management and veterinarians, and access to a Quality Milk Production Services laboratory (Ithaca, Cobleskill, Canton, and Warsaw) for etiologic diagnosis. The farms need to use DHIA services, which includes monthly somatic cell count (SCC) and milk weights. Health records historically should be accurate and include treatment, pen moves, and culling data. Three dairies will be selected by researchers for Monday/Wednesday/Friday sample pickup by QMPS employees. Three additional dairies will be selected for on farm culture (OFC). Dairy managers and employees will be trained to recognize mastitis cases: each CM case will be detected by trained on-farm employees by observing “milk signs” such as abnormal milk including changes in consistency and color or “udder” signs including hard, swollen, or red quarters. Cows exhibiting severe signs such as depression, anorexia, dehydration, or fever will be excluded from the study and treated according to the farm’s protocol for severe CM. Farm managers and employees will also be trained to retrieve milk samples using sterile technique at the time of diagnosis for cows meeting inclusion criteria. An adequate sample will be collected into a milk culture tube from each affected quarter using sterile technique, labeled, and promptly placed in the refrigerator for the Monday/Wednesday/Friday pickup dairies or subjected to on farm culture (OFC) and subsequently placed in the freezer for the OFC dairies.
MWF pickup groups (3 dairies)
Standard culture technique will be performed on all samples by QMPS according to National Mastitis Council (NMC) guidelines for identification of aerobic organisms and Mycoplasma spp.. Briefly, 0.01 mL of milk will be streaked on trypticase soy agar containing 5% sheep blood and 1% esculin (PML Microbiologicals, Mississauga, ON, Canada) and MacConkey’s agar (Hardy Diagnostics, Santa Maria, CA) for identification of gram-negative organisms, and plates will be incubated aerobically at 37°C for 18-24 hours. After observation of colony morphology and hemolytic patterns, isolates will be examined further by means of 3% potassium hydroxide, gram staining, catalase and oxidase testing, and additional biochemical and metabolic evaluations as needed. Mycoplasma will be identified using a dissection microscope after anaerobic incubation at 37°C for 7 days on Mycoplasma agar (Sigma-Aldrich LLC, St. Louis, MO). Culture results will be communicated to the dairy on Mondays, Tuesdays, and Thursdays. The treatment regimen will be based on pathogen: cows positive for Staphylococcus spp., Streptococcus grp G, Streptococcus grp C, Streptococcus dysgalactiae, Streptococcus uberis, or Enterococcus spp. are to be administered one IMM tube of cephapirin sodium (ToDAY®; Boehringer Ingelheim, St. Joseph, MO) every 12 hours for 2 treatments according to label directions. A cow positive for any other organism or no growth on culture plates will receive no treatment. If two organisms were present or mastitis occurred in two quarters, the presence of Staph spp. or Strep spp. will determine treatment in all CM quarters with cephapirin. If it is current farm protocol, a cow with positive cultures for the contagious organisms Prototheca, Mycoplasma, Staphylococcus aureus, or Streptococcus agalactiae will be culled when its meat residue is no longer violative. Protocol instructions will be laminated and posted somewhere accessible at each dairy.
Prior to initiation of the study, the graduate student will deliver and set up an OFC laboratory that meets the needs of each farmer and facilitates easy implementation of the protocol. Two farm employees (a designated person and a “backup” person) will be trained to maintain the incubator at 37°C with appropriate humidity and cleanliness. The employees will also be instructed in proper inoculation of media after sample retrieval. The aseptically collected sample will be cultured on-farm using the Minnesota Easy Culture System (University of Minnesota, St. Paul, MN). This system consists of a bi-plate which is a petri dish with two different types of agar, MacConkey agar on one half selectively grows gram-negative organisms, while factor agar on the other half selectively grows gram-positive organisms. A sterile cotton swab will be dipped into the milk sample and then plated onto the factor media, redipped into the milk, and then applied to the MacConkey media. The plate will be placed in the on-farm incubator and incubated at 37°C for 24 hours. The milk sample that had been collected will be subsequently frozen for QMPS retrieval. The next day the plate will be read and interpreted according to guidelines provided to trained employees. Final results for each sample will be recorded: “gram-positive” for growth on the factor side of the plate, “gram-negative” for growth on the MacConkey side of the plate, “no growth” when bacteria did not grow in either media, or “mixed” when bacteria grew on both sides. The treatment regimen will be based on results: cows with gram-positive growth are to be administered one IMM tube of cephapirin sodium every 12 h for 2 treatments according to label directions. Cows with gram-negative growth or “no growth” will receive no treatment. If growth occurs on both sides of the plate, the affected quarter(s) will receive cephapirin sodium. All CM cows will remain in the treatment pen until milk withdrawal times were met and milk returns to normal visual appearance. Recording of entrance and exit dates into the treatment pen will be encouraged. Any cow that graduates to severe clinical signs may be treated systemically according to veterinary recommendations. Protocol instructions will be laminated and posted somewhere accessible at each dairy.
A post-study verbal survey will be administered to determine aspects of the pathogen-based protocol that the farmer perceived as “successful.” Questions will include ease of implementation, and perception of whether the pathogen-based protocol provided greater treatment success than their initial protocol. Receipts and records will again be valuable to economically evaluate and quantify decreases in antimicrobial product use. Computer records will be assessed monthly for changes in mastitis incidence, chronic mastitis rates, bulk tank somatic cell count, and milk production. Weekly reports of culture results will be sent to the graduate student to evaluate any changes in mastitis etiology during the course of protocol implementation. Repeat mastitis events in the same quarter can also be assessed using retrieved treatment records as well as computer records.
Differences between QMPS culture results will be compared to daily OFC results. The economic analyses and surveys completed in objective 4 for each group of farms will be compared to determine differences between the strategies. Impact of false positives and negatives for OFC will be assessed in accounting for costs of those animals unintentionally treated.
The graduate student will engage farmers once the study has been completed at a joint meeting to query suggestions and communicate successes. Descriptive data as well as any findings noted in objective 5 will be published as a communication article in Journal of Dairy Science. Upon feedback from farm personnel, teaching materials such as powerpoints and handouts will be developed and shared with herd and QMPS veterinarians. We will use these materials to expand our network of outreach. Industry magazines and conferences will offer a platform to further express and communicate our findings.