Promoting sustainability on moderate-sized dairies: Use of a pathogen-based protocol for treatment of clinical mastitis

Final report for GNE16-139

Project Type: Graduate Student
Funds awarded in 2016: $14,926.00
Projected End Date: 12/31/2017
Grant Recipient: Cornell University
Region: Northeast
State: New York
Graduate Student:
Faculty Advisor:
Dr. Daryl Nydam
Cornell University
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Project Information

Summary:

          The purpose was to determine if a pathogen-based treatment protocol for nonsevere clinical mastitis could be effectively implemented on moderate-sized dairies that might not have daily access to a professional diagnostic laboratory.  The study was conducted at 8 moderate-sized commercial dairy farms in central New York (500-100 milking cows).  Two different “diagnostic” groups were investigated.  Dairies in the on-farm culture group (n = 2) were trained to use Minnesota tri-plates to diagnose every case of nonsevere clinical mastitis.  Dairies in the 5-day pickup group (n = 6) submitted milk samples from all nonsevere mastitis cases to Quality Milk Production Services at the Cornell Animal Health and Diagnostic Laboratory 5 days per week and waited 24 hours for diagnostic results prior to the treatment of clinical cases.  Upon receipt or interpretation of results, dairies in both groups followed a treatment protocol decided upon by management and the herd veterinarian.  Briefly, all dairies chose to treat non-contagious Gram-positive pathogens with an intramammary antibiotic according to the manufacturer’s label.  All dairies chose not to treat any quarter with a negative culture result.  Variation existed in regards to treatment of Gram-negative pathogens.   A total of 1,031 cases of nonsevere mastitis were enrolled.  Compliance to the protocol ranged from 59% to 96% and was higher for the dairies in the 5-day-pickup group.  When delayed pathogen-based treatment was practiced, no important changes were noted in monthly mastitis incidence on 7 of the dairies.  Bulk tank somatic cell count was also similar before and after the study for these dairies.  No changes in mature equivalent milk production were seen for the 8 dairies.  One dairy experienced a drop in their bulk tank somatic cell count of 100,000 cells/mL, which can be explained by their apparent increase in monthly mastitis incidence.  This suggests improved proficiency in mastitis detection for this herd.  Overall, inconsistencies and irregularity of data recording, in respect to mastitis events and treatments was drastically improved with implementation of the program.    Reductions in antimicrobial usage ranged from 6.8% to 92.5% dependent on farm protocol and pathogen profile of the herd.  Decreased antibiotic use saved dairies between $2,200 and $4,600 per year when cost of cultures was accounted for.  The use of a pathogen-based treatment protocol based on 5-day per week results or on farm culture results has the potential to decrease antimicrobial use, promote product sustainability, and protect aspects of public health.

Introduction:

          Clinical mastitis (CM) is defined as inflammation or infection of the mammary gland and is detected by visible signs of inflammation such as redness, swelling or pain, and alterations in milk such as clots, flakes, discoloration or abnormal consistency.  This disease remains the most common bacterial disease on dairies and its high incidence (20.4-51.0%) accounts for the majority of antimicrobials administered to lactating dairy cattle (Pol and Ruegg, 2007, Olde Riekerink et al., 2008).  This disease can incur severe economic losses due to discarded milk, reduced production, decreased conception, premature culling, transmission of infection to other cattle, and treatment costs (Fetrow, 2000, Hertl et al., 2014a, b). Current practice on many dairy farms is treatment of all CM cases or “blanket treatment” with intramammary (IMM; into the mammary gland) antimicrobials. In a previous Wisconsin study (Pol and Ruegg, 2007), 80% of antimicrobial drugs used on dairies were used for treatment or prevention of mastitis. However, many organisms that cause mastitis are successfully cleared by a cow’s immune system—a recent shift in etiologies to a majority of gram-negatives or “no growths” rather than contagious or Gram-positive organisms creates an opportunity to reduce the use of antimicrobials. Multiple “treat” and “no-treat” CM regimens have been tested using on-farm clinical trials; results describe  no important differences in clinical outcomes between groups (Lago et al., 2011b, a, McDougall et al., 2018).

            A recent study by our group (Vasquez et al., 2017) used a randomized field trail to assign nonsevere CM cases to either the blanket (BT) or the delayed pathogen-based (dPB) therapy group.  This work was performed on a 3500 cow dairy with a 5-6% monthly incidence of mastitis. Cows in the BT group received immediate IMM treatment with a third generation cephalosporin every day for 5 days. Upon receipt of 24 hour culture results, cows in the dPB group followed a protocol automatically assigned via the dairy computer: Gram-positive organisms such as Staphylococcus spp. and Streptococcus spp. were administered IMM treatment with a first generation cephalosporin for 1 day. Others, including cows with negative cultures or Gram-negative pathogens received no treatment. Statistical comparisons of outcomes were performed between treatment groups for clinical outcomes. The strategic method of treatment decreased the time that milk had to be discarded by 3 days for those cows in the dPB group, with no significant differences in days to clinical cure, milk yield, and linear score post-mastitis event; nor additional odds of culling in the two months following. Greater than 65% of moderate and mild CM cases would not have been treated if all cows were enrolled in a pathogen-based protocol. An additional economic analysis performed on the same data established that >$30,000 per 1000 cows would be returned if this protocol was used at similar dairies. If mastitis treatment decisions are based on scientific reasoning and data indices, economic returns and aspects of public health will be protected. Non-prudent use of antimicrobials as therapeutics can have a negative impact on sustainable agriculture by reducing drug efficacy as pathogenic microorganisms can develop resistance, leading to cycles of prolonged use of the same drug or supplemented use of alternative antimicrobials. Use of antimicrobials on dairies has been shown to have a direct positive correlation to the risk or drug residues in fluid milk sold to processing entities (McEwen et al., 1991).

          Our trial was unique in that it involved a 24 h turnaround of culture results 7 days per week.  Cows experiencing mastitis that eventually went on to be treated (Gram-positive culture results) were only delayed by this short amount of time. Additionally, cultures were performed at a certified diagnostic laboratory allowing for accuracy of results and confirmation of contagious and more obscure organisms. However, many smaller, widespread dairies may not have access to a reference laboratory with a 24 h turnaround. We intended to continue and evaluate our protocol on the more representative, moderate-sized dairies of NY State (500-1000 cows) using either on farm culture, which has been assessed as a rapid and reliable way of diagnosis (Mansion-de Vries et al., 2014, Royster et al., 2014) or a 5 day per-week sample pickup, simulating a veterinary facility or diagnostic lab with the capacity to culture less frequently.

References1   

Project Objectives:

      We wished to evaluate the practicality of a pathogen-based treatment protocol on dairies that do not have daily access to sample submission. To this end, our objective was to create a network of involved and engaged dairy producers to assess two alternatives: less frequent sample retrieval (simulating a 5 day-per-week veterinary laboratory, and on-farm 24h culture diagnosis, or “OFC”). If application of our protocol on these dairies can successfully reduce antimicrobial use by > 60% without negative outcomes, widespread education of the 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.

Cooperators

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  • Dr. Daryl Nydam

Research

Materials and methods:

This study was approved by Cornell IACUC under Quality Milk Production Services #2013-064.

 

            Herd Selection.  The study involved eight Holstein dairy herds in central New York with a herd size < 1000 milking cows.  Each dairy was targeted to enroll 150 cases of nonsevere clinical mastitis between February 2017 and December 2017.  Farm characteristics can be seen in Table 1.  Herds were selected based on their willingness to take samples from mastitic quarters and use on-farm culture (OFC), or to refrigerate samples immediately and notify Quality Milk Production Service (QMPS) at the diagnostic lab at Cornell University for prompt sample retrieval (5d pickup). Farms had to be using IMM antibiotics for the treatment of the majority of mild and moderate mastitis cases to be enrolled.   Farms using QMPS diagnostics had to be willing to delay treatment by 24 h and either treat on the days when sample pickup did not occur, or to wait two additional days for culture results.  Additionally, all herds sending samples to QMPS had to use Dairy Comp 305 (DC305) computer recording, as 24 h culture results were uploaded to this program.  

 

            Enrollment of cases.  All parlor employees were trained to recognize signs of mild to moderate clinical mastitis.  This included abnormal color or consistency of the milk (flakes, flecks, clots), and/or redness and swelling of the quarter.  Any cow that was showing systemic illness including dehydration, pyrexia, or depression was not enrolled in the trial and was treated according to the herd veterinarian’s instructions.  Using sterile technique, milk samples were retrieved from each affected quarter, labeled with the cow number, quarter, and the date, and placed immediately in a 5°C refrigerator. 

 

            On farm culture (OFC) herds.  Farms A and B each nominated one person to be responsible for the microbiological procedures.  Each farm was given an incubator that was to be maintained at 37°C.  Humidity was supplied using a small container of water within the unit.  Training was provided by the author and was supplemented with color handouts, including the Minnesota Easy Culture System guide.  Training included inoculating the agar with sterile swabs, interpretation of the results, and recording of the data.  The media provided was the Minnesota Tri-plate (University of Minnesota, St. Paul, Minnesota), which consisted of three different media on one plate: selective media for Gram-negative bacteria (MacConkey media), selective media for Streptococcus and Streptococci-like species (Modified TKT Media), and selective media for gram-positive and yeast/fungi (Factor Media).  The nominated person initiated cultures on the day that milk samples were collected.  A sterile cotton swab was saturated with the milk sample prior to inoculating each portion of the plate.  The plate was then incubated at 37°C for 24 h.  After 24 h, plates were assessed and the colonies were identified as streptococci, Staph. aureus, CNS, Klebsiella spp., E. coli, Gram-negative bacteria, or other organisms.  Pure growth of one or more colonies was indicative of an infection for all organisms except CNS.  For CNS, more than 3 colonies had to be present to indicate an infection.  Growth of two different colony types was a mixed infection and was recorded as the two different etiologies.  Growth of three or more colony types was contamination and management was instructed to sample the quarter again.  Results were recorded on paper and in DC305 (Herd B) or on paper only (Herd A).  Dependent on result, treatment commenced 24-36 hours after original detection of mastitis.  The remaining portion of the milk sample was frozen at -20°C until samples were retrieved on a weekly basis by the author.  Obvious disagreements between QMPS and OFC results were addressed with weekly feedback and further training.  Technical support was provided throughout the study.

 

            5 day sample pickup herds.  Farms 1-6 were provided instruction for entering culture events into DC305 for each individual case of mastitis.  This included recording the date, quarter, and severity of mastitis.  A printed submission list was generated each morning for the courier, who retrieved samples for 5 consecutive mornings prior to 10:00am.  Results were returned within 24 hours of retrieval and marked as specific culture code within an individual cow card.  Laminated copies of culture codes and their corresponding organisms were posted at each dairy.  Additionally, a printout of each day’s culture results was generated and printed at 11:00am from each herd’s computer. 

 

            Laboratory procedures. Standard culture technique was performed on all frozen samples from herds A and B and fresh samples from herds 1-6 according to the National Mastitis Council’s guidelines for identification of aerobic organisms (National Mastitis Council, 2017).  Briefly, 0.01 mL of milk was streaked on trypticase soy agar containing 5% sheep blood and 1% esculin (PML Microbiologicals, Mississauga, ON, Canada) and incubated aerobically at 37°C for 18 to 24 hours.  Colonies from pure cultures were subjected to matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) using a Bruker MALDI-TOF Biotyper (version 3.1.66; Bruker Corp. Billerica, MA).  Confidence levels were assigned by the machine software by referencing the Bruker 5989 RUO bacterial library.  Levels accepted for species identification were ≥2.0 and for genus identification between 1.8 and 2.0.  The same definitions for intramammary infection were used as described earlier. 

 

            Treatment protocols.  Managers, owners, and the herd veterinarian determined a treatment protocol specific for each dairy.  As not important to our objectives, we allowed each herd’s team to decide what IMM antibiotic(s) to use.  Following assessment of the culture plates at 24 hours, quarters to be treated in the OFC group were treated with the selected IMM product according to the manufacturer’s instructions.  For example, all Gram-positive organisms on Herd A and Gram-positive organisms and Klebsiella spp. on Herd B were treated with an IMM antimicrobial.  All other organisms were not treated.  For the 5 day pickup herds, treatment commenced upon receipt of the computerized results the morning after sample submission.  If a herd elected not to wait the weekend to treat a mastitic cow, IMM treatment could begin immediately, prior to receipt of results. Any cow that graduated to systemic clinical signs was removed from the trial and treated according to the veterinarian’s recommendations.  Farm management was asked to record all treatments in DC305. 

 

            Questionnaires.  Brief initial and follow-up oral questionnaires were administered to individuals directly involved with the treatment decisions on each dairy.  The preliminary questionnaire inquired about the details and costs of the current mastitis treatment protocol, what factors were involved in selecting cows to treat, the primary reason why they wanted to change their current program, and what type of program they think would be ideal.  The final questionnaire asked whether the trial program was effective at their dairy, the most helpful and beneficial aspects of the program, the cost-savings, whether management thought cows were becoming chronic, and what improvements could be made overall.

 

            Analysis.  Initial record analysis prior to the start of the trial revealed that management was not consistent in their recording of mastitis cases or in recording of treatment.  Many dairies did not have established protocols, used protocols including extra-label administration of antimicrobials, or had overlapping/redundant protocols within the computer system or within individual cow cards.  Therefore, monthly mastitis incidence, number of mastitis cases, and chronicity of mastitis (the number of retreated quarters) prior to the start of the trial are likely inaccurate.  As such, any statistical comparison between these benchmarks prior to- and after the trial was not performed.  For other analyses, the unit of analysis was the quarter.  Quarters were excluded from analysis if no culture result was recorded (Herds A and B).  Compliance was calculated as the number of cases for which management followed the decided treatment protocol for each herd divided by the total number of cases cultured for that herd.  Antimicrobial use was calculated as the number of cases receiving IMM antibiotics divided by the total number of cases cultured for that herd.  Chronicity of cases was assessed as the number of repeated mastitis cases over the study period (same cow and same quarter), at least 7 days apart, divided by the total number of mastitis cases for that period. 

            For comparison between OFC and QMPS culture results for herds A and B, diagnoses were binned according to the most prevalent mastitis pathogens on the dairy as well as according to their treatment protocol.  The following categories of growth were described for Herd A: “No Growth”, Staph. aureus, Gram-Positive, Gram-Negative, “Mixed with Gram-Positive,” and “Other”.  For Herd B: “No Growth”, Klebsiella spp., E.coli spp., Gram-Positive, Gram-Negative, “Mixed with Gram-Positive,” and “Other”.  Where Staph. aureus (Herd A) or Klebsiella (Herd B) and another organism were cultured, the result was coded as agreed if the respective organism was reported by the other methodology, irrespective of the second organism.  If a result was contaminated, it was classified as “Other”.  If one result was missing, it was coded as null.  The percent agreement was calculated as the total number of cultures in agreement over the total number of cultures for each herd.  Kappa statistics were used to calculate the overall level of agreement. 

Research results and discussion:

            Individual farm characteristics.  Herd size, bedding type, and the number of quarters enrolled for each farm can be seen in Table 1.  Herds 1, 4, 5, and 6 initially used blanket therapy for all mastitis cases, which was defined as treating each case with an IMM antimicrobial on the date of detection.  Herd A treated all cows with IMM antimicrobials on the day of detection, but discontinued treatment for Gram-negative and “no-growth” cultures when results of the OFC were read.  Herd 2 and Herd B each used OFC prior to the beginning of the trial, but were not consistent with their treatments and did not feel adequately trained on culture plate diagnostics.  Prior to the commencement of the trial, Herd 2 submitted samples to the diagnostic laboratory once per week; treatment of Gram-positive cases was delayed by up to 8 days for some cows.  Only herds 4, 5, and 6 reliably recorded all mastitis events, and only herds 4 and 6 reliably recorded mastitis treatments.  Dairies on the project were taught to record single mastitis events rather than treatments (as some cows would not be treated) and to record all events, regardless of severity.  Consistency was encouraged by creating standard protocols within the computer program.  Overall, this allowed for better epidemiological analysis of mastitis cases, and easier communication between the herd veterinarian and the client. 

 

            Initial questionnaire response. Two of the eight dairies were not satisfied with their current mastitis program.  Half of the dairies believed that their current protocol worked well, but that their overall mastitis program needed improvement. The remaining dairies (n = 2) noted that their current program worked well and needed no improvement; however, they were willing to try something new.  Of all the dairies on the project, the largest dairy had the highest expense for the treatment of clinical mastitis at $25,000 per year.  When expenditures per year were standardized for the number of cows per dairy, between $0.83 and $23.81 was spent on treatments per head, per year.  The most common reason given for enrolling in the program was projected savings on treatment costs.  The remaining reasons were knowledge of etiology (or knowledge of etiology in a timelier manner), and establishing a more effective treatment protocol.  The main factor driving the written mastitis protocol was:  the veterinarian (4), the withhold time of the treatment chosen (1), the ease of direction (1), the effectiveness of the treatment chosen (1), or the individual cow characteristics (1).  The main factors driving whether a cow is treated or not (assuming culling for those herds using blanket therapy) were: milk production, clinical signs, chronicity, and pregnancy status.  According to management, characteristics of an ideal selective treatment protocol would be:  one that offers a prevention strategy or minimizes the need for antibiotics, and one that offers diagnostic driven decisions with minimal turnaround time for results.    

 

            Culture results. A total of 1031 quarters were enrolled in the study.  Using aerobic culture, a pathogen was identified in 65.6% of the mastitis cases.  About 1/3 (34.4%) of cases had no-growth on culture, about 1/3 had Gram-positive organisms (27.3%), and about 1/3 of cultures revealed a Gram-negative pathogen (30.9%).  Culture results by herd are listed in Table 2.

 

            Compliance, Milk, and Milk Quality.    Descriptors, including treatment scheme, compliance, and milk quality and production indices for each dairy can be seen in Table 3.  All herds elected to treat non-contagious Gram-positive organisms and not treat culture-negative cases, but there were several variations on treatment of Gram-negative pathogens and contagious Gram-positive pathogens.  Three dairies in the 5-day pickup group extended their “wait-to-treat”  period over the days when samples were not picked up.  On average, 82.5% of cows were treated according to the established protocol (n=851 cases).  Compliance was generally higher for the 5-day pickup herds as compared with herds using OFC.  Protocols and compliance by herd is shown in Table 3.  The most common form of non-compliance was IMM treatment of cows with Gram-negative pathogens and cows with negative culture results (41.7% of non-compliant cases, n=75).  These were treated due to worsening clinical signs.  The next most common form of non-compliance was non-treatment of Gram-positive cases (due to resolution of clinical signs during the 24 h waiting period; 30.6% of non-compliant cases, n = 55).  Other reasons for non-treatment of cases that should have been treated were: culling of the animal (n = 12, 6.7%), drying the cow early (n = 2, 1.1%), and cases refractory to treatment that management elected not to treat (for example, S. aureus; n = 10, 5.6%).  Finally, 26 culture negative cows were treated that should not have been in one herd due to general miscommunication between management and hospital staff (14.4%).

            Bulk tank somatic cell counts before and after the trial were similar for seven of the dairies.  Herd B experienced a dramatic drop in BTSCC over the course of the trial (Table 3).  Similarly, only small changes were noted in mature equivalent milk production (ME305), a standardized estimation of how much a group of cows would have produced for 305 days, in pounds.    

 

            Retreatment for Clinical Mastitis/Chronicity. Dependent on farm, between 10% and 55% of quarters were retreated for clinical mastitis over the months of the trial and up to two months post mastitis event (Table 4).  For half of the farms, the percentage of retreats appeared to increase as compared with the percentage of retreats before the start of the trial.  Two dairies showed a decrease in the percentage of retreats and one remained similar.  However, mastitis event data was not consistently nor reliably recorded prior to the trial and these comparisons are likely inaccurate.   Monthly mastitis incidence remained similar or decreased for most herds, except for Herd B which appeared to increase 1.4 fold.  This is due to better detection and separation/treatment of mastitis cases during the study as compared with the year before.  This is supported by the large decrease seen in their BTSCC (Table 3).

 

            Agreement between on-farm and laboratory cultures for Herds A and B. The distribution of results between the culture categories that were used to compare culture methods for Herds A and B can be seen in Tables 5 and 6.  The overall agreement for Farm A was 67.3% (kappa=0.58; 95% C.I. 0.49-0.67), with the highest agreement occurring for the Gram-positive cultures (80.5%) and lowest for “Mixed Gram-positive” and “Other” categories (<10%). For Farm B the overall agreement was 55.9% (kappa=0.42; 95% C.I. 0.32-0.51), with the highest agreement occurring for negative cultures (84.3%) and the lowest for “Other Gram-negative”, “Mixed Gram-positive”, and “Other” categories (<10%).  Combined results for Herds A and B result in 188/304 correct diagnoses or 61.8% agreement.

 

            Antimicrobial usage.  The average reduction in antimicrobial usage was 46.4% (range = 6.8% to 92.5%).  The percentage of mastitis cases treated with IMM antimicrobials before and after the study can be seen in Figure 1.  As stated earlier, Herds 2 and B were practicing pathogen-based treatment using OFC without guidance prior to the beginning of the trial.  Guidance reduced antimicrobial use by 6.8% and 20% for Herds 2 and B, respectively.  Herd 3 was also using a pathogen-based treatment protocol, but only submitting cultures once per week.  Quicker diagnostic turn-around led to a decrease in use of 17.2%.  All other dairies, represented by the dark “Before” bars at 100% (Figure 1), were practicing blanket treatment at time of detection.

 

Discussion and Impact:

 

            This study demonstrated that on on-site farm culture systems or provision of off-site culture results 5 days per week can effectively guide pathogen-based treatment decisions for nonsevere clinical mastitis cases on moderate-sized dairies.  On average, a reduction in antibiotic use of 46.4% was experienced.  The variation between farms in terms of protocol design, compliance, and diagnostic accuracy was apparent.  Overall, compliance and satisfaction with the program was high. 

            As the follow-up questionnaire generates much of the discussion for this project, detailed responses are mentioned here rather than in the results section above.  This study was not performed as a clinical trial as in Vasquez et al. (2017); comparisons could not be made between outcomes for cows treated according to the pathogen based treatment protocol and cows treated using a blanket therapy protocol.  Originally proposed benchmarks for assessment of this program were evaluations of chronicity and monthly mastitis incidences prior to and after the trial period.  What became apparent was the inconsistency regarding the recording of mastitis events and treatments.  As such, the best indications for success of the program were 1) maintained or decreased bulk tank SCC, which occurred for all dairies during the trial, 2) maintained or decreasing numbers of mastitis cases in the hospital pen on a monthly basis, which was described by similar monthly mastitis incidences over the trial period, 3) anecdotal reports from farm management.  Seven out of eight dairies believed that pathogen-based treatment was effective at their dairies.  One dairy was not convinced the program was helpful, but moving forward was willing to explore not treating culture-negative cows that were experiencing mild clinical signs.  This dairy owner admitted that a positive aspect of the program would be that 26% of his cows would not be treated with antibiotics. 

            Compliance ranged between 59% and 96% and was likely influenced on OFC herds by confidence in diagnostics.  On farm culture herds listed the following benefits of the trial: continued guidance, knowing etiology quickly, and ability to compare QMPS results to their results.  However, a drawback of the program for OFC herds was the variation in interpretation between QMPS and on farm results.  For Herds A and B, the kappa agreement statistics were 0.58 and 0.42.  These values fall within the “moderate” category of strength of agreement, the third category on a 5-point scale (Altman, 1991). Regardless, the level of agreement is better than by chance alone.  Levels of agreement would have been lower if categorization of culture data was on the species level.  However, categorization was based on those used to assign treatment for each farm.  Errors in diagnosis can lead to different therapeutic choices and over- or under-treatment of mastitis cases.  For Herd A, 15.7% and 8.0% of cases were over- and under-treated, respectively, due to misdiagnosis, assuming that laboratory culture is the gold standard. For Herd B, 12% and 18% of cases were over- and under-treated, respectively.  Evaluation of accurate data would allow one to determine whether under-treatment was contributing to chronicity of cases.  However, given that this was not a randomized clinical trial, it would be difficult to determine if those cases would become chronic, regardless of treatment.  None of the dairies believed that the cows became chronic as a result of implementation of the protocol.

            Greater compliance on all farms and agreement between on-farm culture and laboratory cultures for OFC herds could have been accomplished with greater levels of veterinary input.  Also, herd management was instructed to exclude any animal with systemic signs.  A large proportion of Gram-negative cases were eventually treated with antimicrobials, indicating that perhaps these cases should not have been enrolled.  One must also consider that aside from protocol designation, a combination of factors including parity, stage of lactation, clinical mastitis history, and somatic cell count history contribute to the decisions that herd owners make.  Thus the value of culture data, particularly when highlighting a chronic or unresponsive case, can provide information to assist with culling decisions.  Accordingly, benefits mentioned by dairies in either group during the follow-up questionnaire were the ability to make decisions quickly, particularly for cows that they would cull (not treat), or for those organisms they may elect to treat with additional supportive care.  Decreased treatment costs, and seamless data entry due to loop access between QMPS and the dairies were also mentioned as benefits.  Reductions in antimicrobial usage ranged from 6.8% to 92.5%.  Differences between farms occurred due to dissimilarities in pathogen profile and in choice of treatment protocols.  For example, the combined effect of only treating Gram-positive pathogens in addition to having only 7.5% of cultures positive for these organisms led to a decrease of 92.5% of antibiotic use on Herd 6.  This compares with Herd 5, which elected to treat only negative cultures, of which they only had 27.1%, contributing to a 27.1% reduction.

            Three dairies were intrigued by the recovery rates of untreated cases and believed they were more educated on the behavior of pathogens on their dairies.  Negative aspects of the program were the need to coordinate sampling with parlor workers, difficulty segregating cows once for sampling and again for treatment, and the frustration of experiencing negative culture results.  Suggested improvements were adding weekend pickup, more frequent training of sampling personnel, and establishing more interpretable codes for results within DC305. 

 

            Economic analysis. Accounting for the cost of cultures, savings on antibiotics alone was between $2,200 and $4,600 over the cost of one year.  Several dairies indicated the difficulty of placing value on cows that they were able to cull sooner due to knowledge of etiology.  One of these dairies provided additional supportive care to E.coli-positive nonsevere cases when results were returned; management declared that survivability of these cases increased.  One dairy owner in the 5-day pickup group noted that decreased labor costs should be factored into analysis as he had used OFC prior to the study. 

 

            Farmer Adoption.  Despite the few negative comments on the follow-up survey, all 6 dairies currently pay for continued courier and culture services on a 5-day-per-week basis.  Though no changes in BTSCC were seen for the specific dairy, one herd relayed that mastitis detection has improved due to positive reception of the program by employees. The 2 OFC farms continue to culture their mastitis cases, though both now prefer the use of AccuMast plates (FERA Animal Health, Ithaca, NY) over Minnesota Tri-plates.

Tables-and-figures2

Research conclusions:

            Implementation of culture systems or prompt reporting of culture results by nearby laboratories can effectively drive pathogen-based clinical mastitis treatment decisions on moderate sized dairies, resulting in decreased use of antimicrobials on all dairies involved.  While the two on farm systems experienced moderate agreement with laboratory results, cultures from all eight farms provided data that was useful for decision making, whether for IMM treatments or culling decisions.  For most dairies, no negative outcomes were noted when evaluating chronicity, monthly mastitis incidence, BTSCC, or milk production.

Acknowledgements

            This project was funded by a graduate student grant kindly provided by the Sustainable Agriculture Research & Education (SARE) program, which is supported by the NIH and USDA.  The author thanks the 8 participating dairy owners, management and employees for their contributions to this project.  Herd veterinarians were also crucial to the implementation of the protocols and their continued communications and feedback ensured success. QMPS technicians, couriers, and veterinarians provided and continue to provide services, results and support to the included dairies.

Participation Summary
8 Farmers participating in research

Education & Outreach Activities and Participation Summary

20 Consultations
5 Curricula, factsheets or educational tools
2 On-farm demonstrations
1 Webinars / talks / presentations

Participation Summary:

8 Farmers
Education/outreach description:

Milk-Sample-Collection-and-Handling

plate-reading

QMPS-Selective-Treatment-Protocol-SARE-trial-Venture

recording-sheets

plate-reading

Publications. Future publication of this material as a technical note in Journal of Dairy Science or as an industry article in magazines such as Progressive Dairyman or Hoard’s Dairyman is anticipated.

Outreach.  I will include this material as part of my presentation to the New England dairy nutritionists in March, 2018.

Project Outcomes

8 Farmers reporting change in knowledge, attitudes, skills and/or awareness
8 Farmers changed or adopted a practice
1 Grant applied for that built upon this project
1 Grant received that built upon this project
Project outcomes:

All 6 dairies currently pay for continued courier and culture services on a 5-day-per-week basis.   The 2 OFC farms continue to culture their mastitis cases, though both now prefer the use of AccuMast plates over Minnesota Tri-plates.  In the area of NY that this project was performed on, dairies form a strong network of support, and many share the same veterinarians.  The proposal of this project included 6 dairies.  Through word of mouth of positive reception, two more dairies asked to be included.  We are continuing to see this occur and have had several requests for sample retrieval and training in the area.  Economically, these dairies will save on labor and antimicrobial costs, but also make more informed decisions on culling of animals.  In regards to aspects of public health, prudent use of antimicrobials will likely reduce the risks of residue violations and decrease the impacts of antimicrobial resistance.  With prudent use of the antimicrobial, we likely will preserve effectiveness and sustainability of the product.

Knowledge Gained:

Published trials and data have indicated that the industry can use pathogen-based mastitis treatment protocols on large dairies that have continued support.  However, we were unaware of the ability to practice such protocols on smaller dairies that may not have continued access or support of diagnostic laboratories.  While our attitudes did not change with promotion of prudent use of antimicrobials via use of these pathogen-based protocols, we became aware that many dairies are very willing to learn how to culture on-farm or are willing to pay for 5 days of services so that they can gain more information and subsequently make decisions about their mastitis cases.  We believe that these practices will contribute to sustainability of antimicrobial products.

I hope to continue to provide extension services to veterinarians and dairies in the area regarding prudent use of antimicrobials.  I anticipate a career path that continues to apply and collect knowledge related to best practices.  

Assessment of Project Approach and Areas of Further Study:

Regular monthly meetings including farm management and veterinarians helped to make this project successful.  These meetings included handouts of the progress of the project, estimations of cost-savings, and comparisons as to how other dairies on the project were doing.  Laminated copies of instructions posted where management would be documenting mastitis cases were important for implementation of protocols. 

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.