Developing Management Options for Staph aureus on Organic Dairies

Final report for FNE19-946

Project Type: Farmer
Funds awarded in 2019: $13,157.00
Projected End Date: 12/31/2020
Grant Recipient: Reed Farm
Region: Northeast
State: Maine
Project Leader:
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Project Information


In the summer of 2018, our small organic dairy herd of 33 cows experienced an intense outbreak of Staph. Aureus mastitis. Just over 1/3 of our cows tested positive for this highly contagious organism that is difficult or impossible to treat, and the impact we were seeing was that our milk quality was greatly reduced.

We designed this study in conjunction with our technical advisor to find out if we could manage the Staph. aureus challenge and cull or cure the infected cows over time by:

  • implementing rigorous daily milking hygiene SSOP to prevent spread to healthy udders
  • carefully monitoring Staph. aureus negative cows to determine if the adoption of the protocols results in zero new infections during the one year study period
  • trialing Manuka honey therapy as a dry cow treatment that would be approved under the National Organic Standards to replace antibiotic dry cow treatments typically used in conventional production
  • trialing long dry periods (105+ days) as suggested by experts in New Zealand, that could allow a staph aureus infected cow to “self cure”
  • trialing 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 infections

We found that the milking hygiene SSOP was very effective in preventing spread of the organism between known positive case cows and healthy cows during milking. Key to this SSOP is segregating cows into two groups in either time or space, and sanitizing milking clusters.  Long dry periods were found to be economically unfeasible and did not result in Staph. aureus positive cows testing negative at next freshening. Manuka honey dry cow treatment resulted in one cow who had previously tested positive for Staph. aureus routinely testing negative for the organism. We believe further research may reveal this is a viable organic treatment for cows who are candidates to cure of Staph. aureus (e.g. younger cows who have recently contracted the infection in only one quarter). Milking once a day prior to dry off was adopted as a very effective method of approaching dry off for Staph. aureus positive (and all) cows. 

Overall, the methods and approaches employed in this study allowed us to face a significant herd health crisis that presented economic challenge to our small dairy, in a way that allowed us to maximize milk quality, maximize our paychecks, and cull the Staph. aureus positive cows over time. The Study Summary Handout provides a detailed outline for the organic producer interested in trying these management strategies in the case where a similar herd health challenge should arise for their dairy farm.

Project Objectives:

Our project seeks to test staph aureus management in the practical setting of a working organic dairy:

1) To 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 protocols results in zero new infections during the one year study period. Results will guide us toward development of a clear, written set of protocols for milking hygiene practices that are effective in preventing new infections for mid-lactation cattle.

2) To trial Manuka honey therapy as a dry cow treatment that would be approved under the National Organic Standards to replace antibiotic dry cow treatments typically used in conventional production.

3) To trial long dry periods (105+ days) as suggested by experts in New Zealand, that could 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 infections.


Staph aureus is a very common, highly contagious mastitis organism found worldwide, causing significant economic losses in terms of cattle health, reduced milk quality, and therefore lower pay prices on both organic and conventional dairy farm. Through decades of research we have developed a vast body of knowledge about the organism. Staph aureus bacteria inhabit the exterior teat skin of cattle, especially if the skin is rough, chapped, or unclean. Mid-lactation cattle are vulnerable to contracting new infections from contact with infected milk on equipment or staff’s hands during milking. Cattle also commonly contract at dry-off and freshening if hygiene is not optimal (communications with our technical advisor).

In spite of extensive work, there has not been much success developing effective treatments– research indicates that worldwide, the rate of cured cases is somewhere between 10%-30% for conventional therapies [1]. Neither has there been a solution in vaccines, with a 30% effective rate seen in the US [2].  Perhaps in part through failure to adopt effective preventative management, conventional and organic farms alike continue to be challenged by Staph aureus. Farms rely heavily on cultural management strategies to keep cows clean and dry, milking hygiene to prevent spread through infected milk, and culling of infected cattle to prevent new infections. It is also notable that the organic dairy is at a unique disadvantage in management of staph aureus because antibiotic therapies for dry cows to prevent new infections are not permitted in organic dairy production.

In early 2018, at our organic dairy farm, bulk tank cultures intermittently indicated staph aureus in our herd. We cultured several suspect cows and found multiple infected individuals. Our technical advisor recommended that we test only cattle whose SCCs rise beyond a certain level and display staph aureus’ telltale patterns of rise and fall. Twelve out of a total of 33 lactating cows in our herd were found staph aureus positive, making immediate culling of infected animals an economic impossibility for our small farm. Through conversations with our advisors and other organic farmers in our area, we became aware that we are not the only farm facing this challenge.

Generally speaking, the New Zealand resources on Staph aureus are oriented toward the organic producer and there are some interesting differences from what is currently recommended in the US. Articles describe excellent preventative management as well as promising all-natural dry cow treatments that need further study. In hopes that they might help us avoid culling cows, we plan to trial some of the recommendations from New Zealand. Any lessons that we can learn with successes or failures in this study can help the Northeast organic dairy producer become more aware of these new approaches, and encourage them to make management decisions to reduce the spread of this contagious organism. Healthier, more productive cows, lower cell count milk, and higher milk quality premiums will help move dairies in a direction of greater financial stability.

Because of the economic impact on dairy operations, since the 1960’s, staph aureus mastitis and the problems associated with it have been extensively researched. Much is known about the way the organism inhabits the host, how it is transmitted, and the implications for commercial dairy production. This research has been focused on solutions for conventional production, focusing on finding an effective antibiotic treatment either through trials of treatments, or more recently, through genome research. Some genome studies are indicating that strains of staph Aureus found on organic dairy farms in Europe and the US are less antibiotic resistant than those found on conventional dairies [5].

In spite of the lack of solutions for the conventional producer, research and currently recommended practices still seem to leave the organic dairy producer at a disadvantage. One example is the recommended “cold-turkey” dry off, in which the cow nearing the end of her lactation is provided a lower quality ration to discourage milk production, is moved to an isolated location, and milking of that cow is terminated all at once. The idea is that the teat ends will be sealed once and for all through the cow’s own physiological processes, preventing entrance of the staph aureus organism at a vulnerable time. This approach does not pose much risk in a conventional farm setting where antibiotic therapy is routinely applied intramammary to the cow’s udder prior to the last planned milking, to prevent bacterial mastitis from developing. Additionally, there are no currently organic approved teat sealants to aid in the process. From our perspective as organic producers who cannot use such treatments nor turn to antibiotics if mastitis should occur, there is much greater perceived risk in this management approach.

Preventative health management is one of the central tenets of organic livestock production. As such, we were initially interested in what might be available for vaccinations against staph aureus. Our veterinarian told us that the available options are not very effective. The literature supports this, with studies indicating vaccination is not viable as a stand-alone preventative strategy, and conclusions continue to emphasize milking hygiene as the number one most important approach to prevention of the problem [2].

Throughout our reading, we have found the most promising research coming out of New Zealand, both in that it is oriented toward the organic dairy producer and in that there are some interesting differences from what is currently recommended in the US. Articles describe excellent preventative management as well as all-natural dry cow therapies that need further study. We will test some of those recommendations from New Zealand in this study, incorporating elements into what our technical advisor has recommended. In addition to preventative milking hygiene protocols, New Zealand experts describe potential in the following areas:

  • A mastitis therapy using medical grade UMF 10+ Manuka honey (which meets the US NOP Organic Standards). Manuka honey has been described by farmers as curative anecdotally and has been found effective against staph aureus in laboratory trials in New Zealand [6].
  • Once-a-day milking as a preparation for dry off. This approach appeals to us as a good intermediate step toward “cold-turkey” dry-off that also breaks the cycle of intermittent milking at dry off that leaves cattle vulnerable to new infection and is reported to increase cases of mastitis [6].
  • Long dry periods of 105+ days—twice as long as the 50-60 day dry period commonly practiced in the US—have been observed to allow staph aureus positive cows to eliminate the organism using their own immune defenses. The infected cows “self-cured,” or tested clear of staph aureus at freshening. The long dry period approach would require specifically planned breeding intervals to avoid significant economic losses in terms of reduced milk per lactation. We have identified individual cows in our herd that due to reproductive irregularities would lend themselves as candidates to trial this long dry period approach, and we may be able to identify additional cows for this trial as the year goes on [3].

We hope that adoption of new approaches, if found successful on our farm and elsewhere, might help shape and develop the practices currently recommended in the US to provide the organic producer with greater options than are currently available.

[1] McDougal, 2015.


[3] Organic Dairy & Pastoral Group (ODPG), web resource “Organic Management of Mastitis in Dairy Cows”

[4] Petersson-Wolfe 2010.

[5] Ronco 2018]

[6] Thatcher, 2018.

[7] University of Kentucky Cooperative Extension bulletin, Collecting Clean Milk Samples.

Description of farm operation:

Nate and Katie Webb Clark are a husband and wife team and owner-operators of the Reed Farm in Windsor, Maine. Nate works full-time farming and Katie is part-time. We began shipping organic milk in September 2017 and produce 450,000lbs of milk annually. We have won Gold Quality awards from Dairy Farmers of America. Because we are not a large dairy, production of extremely high quality milk is at the core of our business model. Katie grew up on a conventional and later organic dairy farm, and Nate had worked there milking cows and producing hay and grains since 2012. Katie has a college degree in Environmental Studies with a biology focus.


Click linked name(s) to expand
  • Richard Kersbergen - Technical Advisor (Educator)


Materials and methods:

The original period of this study was 3/1/19 through 3/1/20. As a one-year trial, the study period should in theory encompass one freshening and one dry-off period for each cow in the herd, though in practice, due to breeding irregularities, many cows did not experience both within the study time frame. A second year of study was added to follow individual cows in the experimental dry off methods and manuka honey treatments through their next lactation to determine if the outcomes.

For the study, we divided our herd into two groups, cattle who are known Staph aureus negative (SA-) and those who have tested positive (SA+). Milking hygiene and preventative management protocols will be followed daily in attempt to prevent any new infections to mid-lactation cattle during the study period.

Daily Milking Routine: Hygiene and Management Protocols

  • Milk wearing nitrile work gloves

  • Pre-dip using IBA Bac Stop (iodine) teat dip

  • Wipe teats with single service paper towels

  • Post dip using IBA Genesis Barrier (iodine) teat dip
  • Milk SA- cows first, SA+ cows last, to reduce the chances of exposing healthy udders to the pathogen.
  • Milk SA+ cows last, or, Mark milking units using a yellow plastic flag, after milking SA+ cows, so that milking units that have contacted SA+ cows never contact SA- cows
  • Sanitize milking clusters by dipping first in a bucket of warm water, then a bucket of IBA FS-100 sanitizer for 10 seconds (1/6 oz. per gallon of water to achieve 100ppm) between milking each cow who is SA+ or SCC over 100. Concentration will be monitored with chlorine test strips.

  • Ensure cows dry-off and calve in a clean environment

Each cow who was dried off during the study period received one dry off method (either the “cold turkey” or “once a day” dry off) management.

Additionally, some of the SA+ cows received one trial treatment (long dry period or Manuka honey). This is illustrated in Attachment 3 to clarify how this design allows testing of multiple treatments while still providing a basis for comparison. Cow IDs will be recorded on a chart similar to Attachment 3 to record which treatment was received.

Dry off Methods

1) Cold-turkey dry off. This is the method recommended in the US and that is often used with intermammary antibiotic therapy in conventional production. Cows were confined in the tie stall for up to 7 days, and provided with lesser quality dry hay instead of high quality baleage to reduce the nutrient density to discourage milk production. They were milked until a desired point and then not milked again until after calving. The study had originally included the plan for dry cows to be post-dipped with IBA Genesis Barrier iodine post dip twice daily for 7 days following dry off.
 However, we quickly noted that the post-dipping of cows at dry off was initiating milk-let down, an effect we felt was inhibiting dry off, so this practice was discontinued.

2) New Zealand once a day method. Cows were confined in the tie stall for up to 7 days, as described above, and the cow was milked once each afternoon for a few days up to a month before stopping milking altogether. This was very effective in slowing the lactation and lessened the risk for developing mastitis at dry off.  

Originally our study had FS-106 Chlorhexidine post dip for its effectiveness against S. aureus, however, some of the cows in our herd experienced peeling skin on the teat ends upon switching from the currently used Genesis Barrier iodine post dip. We consulted with our Technical advisor and immediately switched back to Genesis Barrier post dip for the remainder of the study.  Damage to teat end skin is one of the known modes of infection of S. aureus and other mastitis organisms.

The two experimental Dry Cow treatments tested on SA+ cows are as follows:

1) Manuka honey. Just prior to the last milking for cows to be dried off, 5ml of UMF 10+ medical grade Manuka honey was warmed in a small jar placed in a bowl of hot water, 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 will be candidates for this treatment. Cows were be dried off according to the New Zealand once a day method, but 105-120 days before the next due date, rather than the standard 50-60 days.

Sample collection was performed by Katie during routine milking chores, according to the schedule laid out in the project Timetable. We collected samples on a bi-monthly testing schedule for transitioning cattle (those about to calve or to dry off), as a point of reference just before the dry off event and just after freshening, to test dry off methods and dry cow treatments. Dairy One services were utilized monthly to screen for spikes in somatic cell counts (SCC), as an indicator of udder health and potential mastitis infection. Cattle who demonstrated a increase or decrease in SCC were sampled to monitor for new SA infections. A CMT paddle was used between monthly Dairy One test days if new infections might be suspected, or when a fresh cow or heifer was entering the milking herd.

When sampling, each cow’s udder was prepped as for milking, following milking hygiene protocols below. Samples were taken following Clean Milk Sampling protocols as described by University of Kentucky Cooperative Extension bulletin [Attachment 2], except that alcohol prep pads were used for convenience of sanitizing the teat end, at the recommendation of our Technical advisor. Samples were taken on a per-quaker basis to screen suspicious cows, those whose SCC rise to 150 or above, or rise and fall. Test results will allow us to isolate infected milk and to monitor for change.

A CMT paddle was used between monthly Dairy One test days if new infections might be suspected.

Data was compiled 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 were not planned, and were not conducted.

Research results and discussion:

The study began with a herd of 33 lactating cows, of which 12 (just over 1/3 of the herd) had tested positive for S. aureus. Data was compiled 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.

Milking Hygiene Protocols for Prevention. One of the main goals of the management aspect of the study was to prevent new S. aureus infections of mid-lactation cattle using milking hygiene protocols described in our Study Summary Handout. During the study, one cow who previously tested as SA- has tested as SA+. We discussed whether our preventative milking hygiene protocols were at fault, or potentially the case of SA could have previously existed undetected. 

The milking hygiene protocols were effective based on screening of SA+ cows who are routinely milked last, using a dedicated SA milking unit– if the hygiene protocols were ineffective, we would have seen SA+ cattle become SA+ in additional quarters (since each cow has SA in different quarters than herd-mates). For example, a cow with SA in the front-left quarter may infect a herd-mate who had SA in the rear-left quarter, creating a cow with two SA quarters on the left side. However, continuous monitoring reveals that the SA+ cattle have not contracted SA in additional quarters during the study. Essentially the SA+ cows are the most vulnerable mid-lactation cattle in the herd, milked last and using a milking unit that was known to have contacted infected milk, we can conclude that the milking hygiene protocols have been effective in preventing the spread of the organism within the herd during milking chores.

SCC Screening. The benefit of the Dairy One screening in this scenario was tremendous. By following the rise and fall of individual cattle’s SCC scores, particularly the SA+ individuals, we were able to keep high SCC milk out of our bulk tank. We were able to identify suspect cattle, and make culling decisions for the SA+ when their SCC scores soared high and did not cycle back down. We found that the threshold for finding SA+ within the herd was lower than we expected, and we began suspecting cattle with SCC scores above 150. This was unexpected and could be a contributing factor for the undetected cases that remain in a herd infecting herd mates after a farm might attempt to cull out 100% of infected cows. At the same time, there was one cow in our herd with SCC scores that rose and fell in the tell tale manner and regularly stayed above 200, but she never tested positive for SA during the study period. Within the first 6 months of beginning the hygiene protocols, we had gradually removed high SCC cows’ milk from the bulk tank and consistently achieved average SCC scores below 100K which provides us with milk quality premiums in our paychecks. We were very happy with this achievement considering our bulk tank SCC levels soared to over 200K–300K+ during the SA outbreak, before the study began. In conclusion, SCC monitoring is essential in successfully managing a SA outbreak in a small herd.

Dry cow trials:

100+Day Dry Period Treatment. In the 100+ day dry period trial, two SA+ cows received this treatment. The first trial cow developed mastitis in the middle of the dry period, and miscarried her calf. The infected quarter was sampled and was not S. aureus, but in effort to receive return on the animal before serious illness developed, the cow was culled from the herd before lab results were returned. In the second trial, the SA+ cow successfully completed the 100+ day dry period, delivered her calf, and was found to have acute mastitis in the udder. Being a known SA+ cow, and being in good body condition, she was quickly culled from the herd to avoid developing serious illness and decline. The mastitis culture revealed SA mastitis in 3 of her quarters. In sum, no cows receiving the 100+ day dry period successfully completed the treatment or remained in the herd at the end of the trial. This potential method of control merits further study, in our opinion, in a setting where the conditions are right such as a herd whose breeding intervals are longer than ideal.  In conclusion, considering the great cost of this approach in terms of milk revenue lost, we concluded this is not a viable practice for a farm our scale.

Manuka Honey Treatment. In the Manuka honey dry period trials, all cows had detectable SA upon next freshening except one who had results of interest. This particular SA+ individual tested positive for SA only intermittently, not predictably, throughout the lactation. This cow was treated with Manuka honey at dry off as described in Methods. She received a typical length dry period and freshened with a clear udder (no mastitis and low SCC). Her 4 quarters were cultured and SA was not detected.  She has been re-sampled monthly and SA has not been detected on any occasion. On test days, this animal’s SCC was always below 50,000 indicating that the SA infection was cured during the dry period.  Upon discussion of these results with our Technical advisors, we have come to understand that SA is sometimes treatable if the SA infection is relatively new, meaning the organism has not had a chance to encyst within the udder, scarring to form, and the condition become chronic.  This was the case for this particular cow receiving the Manuka honey dry treatment.

Mid-lactation Manuka honey experiment. In addition to the Manuka honey dry treatment, intermammary Manuka honey treatment was trialed on one mid-lactation SA+ cow who broke with severe mastitis. This was not a planned part of the original study.  The mastitis was cultured and confirmed to be SA mastitis. Manuka honey was dosed repeatedly into the infected quarter. We did not see a curative effect. The cow continued to sicken and was not able to recover from the illness.

Dry off methods:

New Zealand Once-a-day milking for dry off. In dry cow trials, it was rapidly apparent that the New Zealand once-a-day dry off method offered a viable strategy for preventing new cases of mastitis at dry off.  In that the act of milking stimulates further milk production, by milking once daily rather than twice daily, the cow experiences reduced demand for milk and the milk production level dropped, yet at the same time, the cow still received the relief of being milked. With a lowered production level, the cow is better prepared for the final milking prior to dry off and mastitis was not observed upon freshening. Our fresh cow SCC numbers appear much lower for SA- cows than before the study.  We quickly decided we would adopt this as a viable new practice and will use this approach going forward. There was no apparent relationship between once-a-day dry off method and SA status of cows. We did not see a great increase in new cases of SA as we adopted this practice, indicating that at least in combination with preventative milking hygiene, once-a-day milking prior to dry off did not increase our cases of SA mastitis. Additionally, as the study progressed and our herd SCC averages came down dramatically, we observed our mid-lactation SCC scores were consistently lower for SA- cows than before the study. There may be a viable research question in whether once-a-day milking results in statistically significant reduction in SCC counts for mid-lactation cows.


Research conclusions:

In conclusion, the implementation of the various parts of this study on our farm has helped our family-scale organic dairy minimize our financial losses as we navigated a significant herd health crisis.  We tested staph aureus management in the practical setting of a working organic dairy:

Milking Hygiene. In conclusion, we can see that that the adoption of the recommended milking hygiene protocols benefitted our farm much more than culling all SA infected cattle at the onset of the outbreak.  The hygiene protocols were clearly able to prevent uncontrolled spread of the organism while culling in a gradual, more economically feasible way. It took some time for the SCC screening to help us identify cattle whose SCC levels were routinely problematic and remove their milk from the bulk tank, but we did not face the negative financial impact of dramatic loss in milk volumes that we would have if we culled all the SA+ cows at one in attempt to control spread in the herd. Additionally, we understand that many herds find that new cases of SA pop up even after culling all known SA+ cows from the farm.

SCC Screening. The Dairy One screening in this scenario was invaluable in reducing our bulk tank SCC levels from over 200K–300K+ during the SA outbreak, before the study began, to average SCC scores routinely below 100K. This restored our ability to achieve milk quality premiums in our paychecks. In conclusion, SCC monitoring was essential in successfully managing the SA outbreak in our small herd.

Manuka Honey Treatment. In the Manuka honey dry period trials, all cows had detectable SA upon next freshening except one who had results of interest. These results suggest there is some possibility that this case of SA was eliminated through the use of Manuka honey dry treatment. We believe that Manuka honey merits further study as a potential treatment of SA and other types of mastitis.

100+Day Dry Period Treatment. Conclusions on the efficacy of the long dry period as a method of treating SA were not able to be drawn from this trial.  Considering the culling of the cows involved in this trial, and the great cost of this approach in terms of milk revenue lost, we concluded this is not a viable strategy for a commercial farm at our scale. 

Once-a-day milking prior to dry off. As a result of the positive outcomes we observed associated with this method, we quickly concluded we would adopt this as a viable new practice and will use this approach going forward. There may be a viable research question in whether once-a-day milking results in statistically significant reduction in SCC counts for mid-lactation cows.

Overall conclusions:

In the course of our study, our herd went from 33 cows with 12 positive cases of SA, to 38 cows with 5 positive cases. One positive case of SA in the Manuka honey trial appears to have been cured. The management protocols we adopted prevented the spread to healthy cattle, and we were able to maximize the quality and volume of milk in our bulk tank, and therefore maximize our paychecks. As a direct result of engaging in this study, by investing a lot of time and energy in monitoring the herd udder health as outlined in the study, our small family farm operation is in a much better position in terms of being financially viable at the conclusion of the study than following our SA outbreak prior to the study. Through adopting the activities under Methods, we have identified which strategies helped our success, and we have adopted these new practices. We hope that our trials and conclusions will help others with similar operations face the challenge of managing S. aureus on an organic dairy.






Participation Summary
1 Farmer participating in research

Education & Outreach Activities and Participation Summary

1 Curricula, factsheets or educational tools

Participation Summary

1 Farmers
1 Number of agricultural educator or service providers reached through education and outreach activities
Education/outreach description:

Our plans for delivery of multiple in-person talks about the research needed to be scaled back as in-person events were cancelled, rescheduled, and shifted to virtual formats in the best case scenarios. We developed a Study Summary Handout that contains the technical information from our Methods section as would interest a farmer who might like to replicate parts of the study, and this was shared through the Maine Organic Milk Producers email listserv.
FNE 19-946 Summary handout


Learning Outcomes

1 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key areas in which farmers reported changes in knowledge, attitude, skills and/or awareness:

Greater understanding of an economically significant mastitis organism

Adoption of improved milking hygiene practices was demonstrated to effectively prevent new infections


Project Outcomes

1 Farmers changed or adopted a practice
1 Grant applied for that built upon this project
1 New working collaboration
Project outcomes:

Through the course of implementing the Methods section of our study, my husband and I have become habituated to SSOPs that benefit our farm. The additional steps in milking are extra work and time consuming, but because we stuck with them since the time our study began in early 2019, and because the benefits of sticking with them were so readily apparent as we carefully tracked our mastitis and SCC data for the study, the study protocols are now ingrained in how we do our daily work. It would be unthinkable for me or my husband to re-use a milking cluster that had contacted a known Staph. aureus positive cow, even on another known positive cow, without sanitizing it first.  I think this level of commitment to preventative protocols is necessary for a farm to overcome a challenge as great as what we faced.

Through the course of the study, I became very familiar with working with the UMaine Diagnostic lab, and we saw that Staph. aureus is not the only mastitis with significance affecting our herd. Going forward, I will not hesitate to culture our cows and see the benefit of knowing which type of organism is responsible for the udder health symptoms that we observe on a day to day basis.

Another benefit was the support that we received from our advisors through regular interactions as the study was designed and methods were implemented. We would regularly check in with Rick to discuss how our SCC scores were looking and how we were dealing with the Staph. aureus positive cow cases that we were managing in the herd for the study. There are times when we were trying to keep positive cows in the herd to benefit the study, but their levels were soaring so high and the risk of infection was so great that we just simply needed to move that cow on from the herd. This support and perspective was extremely appreciated, and helped our stress levels surrounding our response to the challenge as we got organized, put protocols into place, and within several months got the organism under control in our herd. 

Assessment of Project Approach and Areas of Further Study:

There is no question that the Methods that we developed for this study will continue to be a part of our daily milking routine for as long as we milk cows, even if we should reach a point where we believe that S. aureus has been eliminated from our herd. We also revised our dry off protocols and settled in with an approach that fits our cows and our farm’s infrastructure.

Looking back, because of the length of cow lactations and dry periods, a two year study would be ideal. That would encompass more results in tracking individual SA+ cattle through their treatments, dry periods, and into their next lactations. We designed a second year study to follow this up, but there were significant challenges in getting our samples to the lab in a timely manner during the lockdown and pandemic months that are ongoing.

Now that we have a good handle on Staph. aureus as an organism, if we were to replicate the study but could employ the observation and monitoring skills that we learned in the first year, I don’t think we would need to screen the cows using lab samples as often. Our original methodology called for testing twice per month. It would be important to take samples prior to dry off, at freshening, and anytime that mastitis symptoms flare up. 

Our results suggest that large scale study on Manuka honey therapy for mastitis is merited. Our one example of a cow whose profile is considered “curable” based on our advisors’ technical knowledge and never tested positive for S. aureus again after Manuka honey dry treatment ended up feeling a bit anecdotal, but does suggest that a larger study may yield results of interest.

Within the first half of the study, our Methods were successful at getting our paycheck back where it needed to be after suffering from negative milk quality impacts from the mastitis outbreak. This has potential to help any dairy, organic or conventional alike, where Staph. aureus has impacted milk quality to the degree that there are deducts in pay price or quality premiums can not be achieved. This is essential to the viability of the farm. 

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.