Developing Management Options for Staph aureus on Organic Dairies

Progress report for FNE20-965

Project Type: Farmer
Funds awarded in 2020: $13,149.00
Projected End Date: 05/31/2021
Grant Recipient: Reed Farm
Region: Northeast
State: Maine
Project Leader:
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Project Information


Staph aureus is a common contagious mastitis organism worldwide, causing significant economic losses on both organic and conventional dairy farms. Decades of research have developed extensive knowledge about this antibiotic resistant organism, but successful treatment and prevention through vaccination remains low, and the challenge remains for farmers. Management of the problem relies heavily on culling infected cows and on cultural practices to prevent new infections of healthy cows. In the summer of 2018, we experienced an outbreak of Staph aureus on our organic dairy. About one third of our herd tested positive, including several young cows, making it cost prohibitive to cull of all the infected cows. This proposal seeks to test recommendations from New Zealand that may help prevent new infections, and that show potential to help cows overcome existing cases. For this study, we will adopt rigorous milking hygiene and cattle management practices as part of our day to day operations, and trial new dry cow treatments and management approaches. We will culture milk samples of Staph aureus positive and negative cows on a frequent testing schedule to evaluate the efficacy of the dry cow treatments and aim for 100% prevention of new cases in mid-lactation cattle during the study period. We will share our findings electronically through frequently used online dairy forums, a presentation at Wolfes Neck Center’s Organic Dairy Farmer Training Program in Freeport, ME, and a presentation at a milk quality workshop in cooperation with the Maine Organic Milk Producers and UMaine Cooperative Extension.

Project Objectives:

In a second year of study testing staph aureus management in the practical setting of a working organic dairy, our research would seek to:

1) Test the effectiveness of milking hygiene and preventative management protocols from the US and New Zealand. We will monitor staph aureus negative cows to determine if the adoption of the recommended practices results in zero new infections—100% prevention—during the one year study period.

2) Trial Manuka honey therapy as (a) a dry cow treatment, and (b) a mid-lactation mastitis treatment; this would be approved under the National Organic Standards to replace antibiotic treatments typically used in conventional production. The mid-lactation treatment a new study question for the 2020 study.

3) Trial long dry periods (105+ days) as suggested by experts in New Zealand, that may allow a staph aureus infected cow to “self cure”.

4) Trial dry-off strategies. Cold-turkey dry-off and New Zealand once-a-day dry-off will be compared for staph aureus negative cows to see if one strategy is preferable for preventing new mastitis infections.


Staph aureus is a common mastitis organism affecting dairy herds worldwide, causing losses in cattle health, reduced milk quality, and therefore lower pay prices on both organic and conventional dairy farms.

Decades of research have developed a vast body of knowledge about the organism. S. aureus bacteria inhabit the exterior teat skin of cattle, especially if the skin is rough, chapped, or unclean, and inhabit unclean areas in cattle barns and yards, such as wet alleys, muddy pasture lanes, and maternity pens if not properly cleaned.  Also highly contagious, lactating cattle are vulnerable to contracting new infections from herd mates during routine milking, via droplets of milk left inside the milking unit, or on staff’s hands. Cattle also commonly contract S. aureus mastitis at dry-off and freshening if hygiene is not optimal (communications with our technical advisor, Rick Kersbergen).

Perhaps in part through failure to adopt effective preventative management, conventional and organic farms alike continue to struggle with Staph aureus. Some conventional farms in our area have 100% positive tests for S.aureus in their herds (communications with our co-op’s field rep). A major challenge is that in conventional dairy systems, S. aureus has developed antibiotic resistance; research indicates that worldwide, the rate of cured cases is between 10%-30% for conventional (antibiotic) therapies [1].  For the rare cases when S. aureus has been seen to clear, it is typically young cattle, early in lactation, with a S.aureus infection that has not yet become chronic (communication with our technical advisor, Dr. Townsend). Vaccines have been developed, but a low 30% effective rate seen in the US [2]. Therefore, farms rely heavily on culling infected cattle (moving them to the beef market) to prevent new infections. The loss of milk price for lower milk quality and the heavy pressure to cull infected cattle cause significant economic losses for farms.

In early 2018, at our farm, bulk tank cultures intermittently indicated staph aureus in our herd. Our technical advisor recommended that we test cattle whose SCCs rise beyond a certain level and display S. aureus’ telltale patterns of rise fall. Twelve out of 33 lactating cows in our herd (about 1/3) were found staph aureus positive, making culling of infected animals an economic impossibility for our small farm. Through conversations with Rick Kersbergen, we became aware that we are not the only farm facing this challenge.

Rick provided us resources from New Zealand on Staph aureus that are oriented toward the organic producer and offer interesting differences from what is recommended in the US. Articles describe excellent preventative management as well as promising all-natural dry cow treatments including Manuka honey and long dry periods. We developed the New Zealand recommendations into a SARE Farmer grant which was funded in 2019.  We have some exciting preliminary results from our study, suggesting that S. aureus can be sequestered within a herd and existing infections may be successfully treated with medical grade UMF 10+ Manuka honey as a dry cow treatment.  This 2020 proposal adds a greater focus on Manuka honey treatment of mid-lactation SA+ cattle, in order to further explore the potential of Manuka honey intermammary treatment.

During a chance late-night emergency vet call with Dr. Townsend, we began discussing our 2019 SARE Farmer grant, and he expressed interest in learning more about our research questions. We shared our proposal with him and our primary technical advisor, Rick Kersbergen, suggested we invite Dr. Townsend on board as a co-technical advisor for our 2020 proposal, to lend his veterinary expertise to questions such as, how do you know when a chronic S. aureus infection is 100% cured, since the organism can encyst in the udder and maintain dormancy for some time.

While the number of conventional and organic dairy farms in the US is steadily shrinking since 2012, the number of organic dairy farms was around 2,500 nationwide in 2016.  All dairy farms could benefit from our research if we are successful at managing the Staph aureus organism to maintain milk quality, treating the organism with organic-approved medical grade Manuka honey and/or long dry periods, and sharing our results with a wide audience. Any lessons that we can learn with successes or failures in this study can help the organic dairy producer become aware of alternative approaches, and encourage adoption of preventative practices. Healthier, more productive cows, lower cell count milk, and higher milk quality premiums will help move dairies in a direction of greater financial stability.


Click linked name(s) to expand
  • Richard Kersbergen
  • Dr. Matthew Townsend, DVM


Materials and methods:

In 2019 we received a SARE Farmer Grant with a one year trial period, in theory encompassing one freshening and one dry-off period for each cow in the herd.  At Carol Delaney’s suggestion, we are applying for a second year of study, in order to follow cows through complete gestation cycles (including the dry period), since S. aureus outbreaks often occur during stressful times such as calving and early lactation.

For the study, our herd is divided into two groups, cattle who test Staph aureus negative (SA-) and those who have tested positive (SA+).

The Milking Hygiene and Preventative Management Protocols as used in the 2019 study will remain unchanged during the 2020 study:
• Milk wearing nitrile gloves
• Pre-dip using IBA Bac Stop (iodine) teat dip
• Wipe teats with single service paper towels
• Post dip using IBA Genesis Barrier teat dip
• Milk SA- cows and SA+ cows separately, by marking milking units with orange flagging tape for milking SA+ cows
• Sanitize milking clusters by dipping first in warm water, then a bucket of IBA FS-100 sanitizer for 10 seconds (100ppm) between each cow. Concentration will be monitored with chlorine test strips
• Ensure cows dry-off and calve in a clean, dry environment.

Each cow will receive one dry-off method (either the “cold-turkey” or “once-a-day” dry-off) management. Additionally, SA+ cows will receive one trial treatment (long dry period or Manuka honey). This is illustrated in Attachment 3 to clarify how this design will allow testing of multiple treatments while still providing a basis for comparison. The following dry-off methods will be tested to evaluate if dry-off procedures influence new infections during dry-off and then at freshening. We will randomly assign all cows into one of three dry-off treatment protocols:

Dry-off Methods:
1) Cold-turkey dry-off. This is the method that is often used with intermammary antibiotic therapy. Cows will be provided with lesser quality dry hay instead of high quality baleage to reduce the nutrient density thereby discouraging milk production. They will be milked until a desired point and then not milked again until after calving. Dry cows will be post-dipped with Genesis Barrier post dip twice daily for 7 days following dry off.
2) New Zealand once a day method. We will reduce ration quality as above, and milk the cow once each afternoon for 3-5 days before stopping milking. Dry cows will be post-dipped with Genesis Barrier post dip twice daily for 7 days following dry-off.

Dry Cow treatments to be tested on SA+ cows:
1) Manuka honey. Just prior to the last milking for cows to be dried off, 5ml of UMF 10+ medical grade Manuka honey will be warmed and dosed intermammary into an SA infected quarter using a single use sterile syringe and massaged in thoroughly.
2) Long dry period. SA+ cows with sufficiently long breeding intervals are candidates to be dried off 105-120 days prior to their due date, rather than the standard 50-60 days.

Mid-lactation SA+ treatment: This is new for 2020. During a period of elevated SCC indicating S. aureus is active, mid-lactation SA+ cattle will be dosed intermammary with 5ml of UMF 10+ Manuka honey as a treatment of the infection, once daily, for 7 days.  Milk from treated cows will be discarded and not enter the bulk tank for human consumption.  These cows will be cultured immediately before, and for several months after, the Manuka honey treatment to detect if S. aureus is still present after treatment.

Milk sample collection will be performed by Katie and Nate during routine milking chores, according to the description in the project Timetable. We will collect samples for culturing monthly for: (a) SA- mid-lactation cows whose SCCs rise above their normal levels, to monitor the effectiveness of our milking hygiene protocols; (b) transitioning cattle (those about to calve or to dry off in preparation for calving), as a point of reference just before the dry-off event and just after freshening, to test dry-off methods and dry cow treatments; and (c) any other cattle of interest, such as those who have received Manuka honey treatment, to monitor for success of the treatment.

When sampling, udders will be prepped as for milking. Samples will be taken following Clean Milk Sampling protocols [Attachment 2]. Composite samples (a combination of milk from all quarters) will be used for routine screening of SA- cows. Samples will be collected and frozen for 5-6 consecutive days, then combined as a composite, to increase the likelihood of catching the intermittent shedding of the staph aureus organism, reducing the chances of false negative results. If a SA- cow is found SA+, we will re-test culturing samples from each teat to learn where the infection is. Individual teat samples will be taken from identified and suspect SA+ cows to allow us to isolate infected milk and to monitor for change.

Monthly milk testing will be conducted on the whole herd using Dairy One services to monitor somatic cell counts as an indicator of cow health and to screen for potential new mastitis infections. We will also test using a CMT paddle between monthly Dairy One testing if new infections might be suspected.

Our veterinarian suggested vaccination for S. aureus to help prevent new infections. We will vaccinate all members of the herd down to age 4 months using Lysigin (Boehringer Ingelhiem), recording this in cattle health records.

Milk culture data will be recorded in a spreadsheet on a per-cow basis for SA- cows and per-teat basis for SA+ cows in chronology, in effort to correlate any changes in SA status of individual cows with events such as dry off and freshening, as well as changes in SCC that could be used as indicators of staph aureus flare ups or new infections.

Statistical analyses of our data are not planned, however if our findings appear to indicate trends, statistical analyses will be performed in cooperation with technical advisors to determine if statements can be made about cause and effect.

Participation Summary
1 Farmer participating in research

Learning Outcomes

1 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation

Project Outcomes

1 Farmers changed or adopted a practice
Assessment of Project Approach and Areas of Further Study:

The sampling schedule described in the Timetable, and therefore the resulting data set achieved in the 2019 study, were highly ambitious and allowed us to evaluate the effectiveness SSOPs and experimental treatments being tested in this study to a degree where we may be able to hypothesize about causation for new cases of Staph Aureus mastitis contracted during the study period (e.g. was the case contracted before the dry period, during the dry period, after freshening, or mid-lactation through contact with infected milk of a herd mate, etc.). However, over the course of 2020, the Covid-19 pandemic limited our ability to keep with that same Timetable in submitting lab samples, and over time, delays have led to a smaller and less complete data set on the mastitis status of our herd in 2020.  We are working with our main Advisor, Rick Kersbergen, to determine in what ways our study questions may be revised or adapted to maximize the benefit of the work sampling work that we were able to do. It should be noted that the 2020 study work, (as with the 2019 study) is based on strict adoption of the same set of milking hygiene protocols designed for the first year study, and at no time during the 2020 research period have we deviated from those protocols during our daily work. In fact, we have found the hygiene protocols so helpful and effective, while remaining practical, that I anticipate that we will use them indefinitely as long as we are milking cows.

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.