Mastitis and milk quality: current topics on the 2016 World Buiatric Congress

world buiatric congress Dublin

Udder Health Session; Monday 4th July

Keynote: Predictive Biology

Martin Green. University of Nottingham, UK

Predictive biology uses knowledge of basic biological processes and mechanisms to foresee diseases and their control.

Modern dairy farming possesses the ability to create substantial numbers of data on farm: location of cows in the barn, activity, pathogens and cell counts and cow genetics. There is plenty of data, computers offer us the ability to calculate big data, but currently we are not using this information for actual forecasts. We first have to understand the underlying biology and then create the meaningful questions to be answered.

Predictive biology can be used for assessing the individual cow susceptibility. By looking at genomic traits for instance, we can identify which cows are more likely to become ill. Mastitis is a highly polygenic disease. Genomic markers can be used in bull selection, but also in selecting young stock to be kept on farm or even earlier in embryo selection.

Genes are not the only influencers. Also environment impacts the susceptibility, either direct or through modification of genes (epigenetic effect). In mastitis, there is more and more evidence that the mammary microbiome (the ecological community of commensal, symbiotic and pathogenic micro-organisms) have an impact on immunity and health. The microbiome is now seen as the “second genome” and acts as such as a modifier of the genetic susceptibility of a cow. It forms an essential component of immunity and influences metabolism. There are differences found in the microbiome between cows having different levels of cell count, but more work is needed to know whether this really influences the susceptibility to mastitis and whether the microbiome changes over time within cows. We also still need to determine when and how the microbiome is formed and whether we disturb it with DCT or dipping practices. Having more knowledge will assist us to find out how we could use the microbiome to safeguard cows.

Another path for predictive biology is the differentiation of pathogenic subspecies. If we understand pathogens better, we can better forecast the prognosis of mastitis cases. For instance in the work of Ruth Zadoks, Streptococcus uberis could be classified into contagious and environmental strains. If we could diagnose which type of S. uberis is infecting our cow, we could take better decisions on intervention. It turns out that 33 out of 52 farms have at least 1 potential strain that spreads contagiously and in 17 farms, the potential contagious strain accounted for more than half of the mastitis cases. Those strains were more closely related than the environmental strains, this means their underlying biology was more similar. If we could identify this underlying biology, we could predict mastitis better on farm. Maybe in the future we might use protein profiles to discriminate between contagious and environmental strains.

A third example of the potential use of predictive biology is the use of stochastic models. These computer models have often been used in research, but we need to be able to translate them into clinical decisions. They could tell us how to extrapolate from a study population to a particular herd. They are a way of considering a lot of changes in a context well beyond what we can test in a randomized clinical trial. We can do “what if” analysis, find why or under which circumstances certain special outcomes might happen. Since resources will be limited on a dairy unit, when assessing competing disease control strategies, it would be valuable if interventions could be evaluated and prioritised not only according to probable efficacy, but also to likely return on investment. You could also find the true relative cost of the negative impact of fertility on mastitis for instance.

Early diagnosis of mastitis pre-partum with infrared thermography

Patricia Simoes. SRUC, UK

The infrared thermography technology could potentially be used to diagnose mastitis early, pre-partum because it is an easy, fast and non-stressful tool. A study was carried out with 126 heifers in their last trimester of pregnancy. They were thermographed 2 months and 2 weeks pre-partum, both with caudocranial and ventrodorsal projections with a distance of 70 cm from the udder.

The pictures were analyzed with appropriate software with regular digital pictures of the same udders as a reference. At calving, milk samples were taken for bacteriological investigation and measurement of somatic cell count. Preliminary results showed that no distinct patterns could be found to predict infection at calving.

Milk microbiome assessed during antimicrobial treatment of mastitis

Erika Ganda. Cornell University, US

In this survey researchers analysed the cure rate of Gram negative and culture negative mastitis cases after 5 day treatment with antibiotics. At the same time, the effect of mastitis and antibiotics on the microbiome was evaluated by comparing healthy and mastitic quarters of the same cow. Also the over-time effect of prolonged antibiotic therapy on microbial profiles of mastitic milk was evaluated. 80 cows were enrolled and were randomly divided into a treatment (5 days ceftiofur intramammary) and a negative control group.

The results showed that cure was not any different for the control versus the treatment group. In terms of bacterial load and diversity, there was a treatment effect on the 3rd day of the treatment course, but no effect remained on day 8 or 13.

When looking at the microbiome, healthy quarters were always more diverse than mastitic quarters, except when mastitis was culture negative. The bacterial profile of healthy and mastitic quarters from cows diagnosed with no bacterial growth under aerobic conditions did not significantly differ.

Are bacteriological results any different when the milk sample was taken with or without a cannula?

Mari Friman. University of Helsinki, Finland

The researchers were wondering whether the result of a bacterial culture of a milk sample would be any different when the teat was inserted with a cannula during sampling, as opposed to normal aseptic sampling technique.

They collected milk samples from 149 quarters from 88 cows from 44 farms, from both clinical and subclinical mastitis cases. Every cow was sampled first with the conventional technique. Then the teat was desinfected again and a cannula was inserted into the teat canal to collect a second milk sample.

Results revealed that conventional technique resulted in more species than the cannula technique. Especially more CNS, yeast and Trueperally pyogenes were found in the conventional taken samples.

This suggests that the canula technique might prevent contamination from environmental germs into the milk sample.

Are dairy farmers interested in mastitis diagnoses?

Karien Griffioen (presented by Annett Velthuis). GD, The Netherlands


Recent studies in the United States have shown that on farm culture of mastitis cases could result in a considerable reduction in the use of antibiotics. This would be an interesting concept in The Netherlands, where the use of antibiotics is now very restricted. A survey was therefore carried out to check the opinions of dairy farmers on mastitis diagnoses. Surveys were performed by telephone interview with approximately 200 dairy farmers.Only a third of the farmers used bacteriological culture for clinical mastitis, but it was only seldomly used to decide on the actual treatment choice. They would be interested in a more rapid test if it could tell whether antibiotic therapy is necessary and which antibiotic they should use. A majority of vets (51%) but even a larger majority of farmers (71%) would be interested in such a test. The reliability of the test would be the most important characteristic, over speed, usability and price.



A cost-effectiveness analysis of on-farm culture for the treatment of clinical mastitis

Peter Down. University of Nottingham, UK

A previous study (Lago et al.,2011) showed the feasibility of on-farm culture and defined benefits of it in terms of reduced antibiotic use and more targeted and so responsible use of antibiotics. In that study, gram negatives showed a reduced cure rate of 60% compared to 71%. While that was statistically not significant, it cannot be excluded that it is economically relevant if it were true. A probability sensitivity analysis was carried out to know the factors that influence the cost effectiveness of on farm culture.

The input in the computer model was based on the Lago study. Based on the results, on farm culture would be cost effective when the percent of gram negative mastitis is large and when there is a small difference in cure rate between treated and non-treated gram negative mastitis.

Could dogs smell Staphylococcus aureus?

Carola Fisher-Tenhagen. University of Berlin, Germany

It is not new that odor can be a valuable diagnostic tool. It was already used in the middle ages by doctors, and it is now implemented in diagnosis of tuberculosis by rats in Africa.

At the University of Berlin, dogs were previously trained dogs for heat detection. They were now interested to know whether they could be valuable in diagnosing disease as well. 10 dogs with experience in scent detection were selected from a training school. First they learned to select the odor of S. aureus directly from a plate. As controls, the researchers offered plates with S. uberis, yeast, E. coli and other common mastitis germs. The plates were placed in a plastic container on the floor and the dogs were asked to indicate the plate with the S. aureus culture. After a training period, the dogs were able to detect the S. aureus samples with a 91.3 sensitivity and a 97.9 specificity. This proved that S. aureus has a specific odor and that dogs can be trained to detect it.

In a second stage, the researchers inoculated fresh milk. At first the dogs were confused and some lost interest in the experiment. After increasing the bacterial load in the inoculation, the remaining dogs were again able to detect the samples with 83.3 % sensitivity and 98% specificity. In the last stage of the experiment, the dogs had to detect real mastitis samples. They achieved a sensitivity of 59% and a specificity of 93%. Maybe these results can still be increased with continued training. Anecdotally, there were some individual differences as one dog was able to achieve a 85.7 % sensitivity and a 96.9 specificity. These results could offer further possibilities for detecting S. aureus, maybe even with an electronic nose.

Potentials and challenges for diagnosing udder pathogens with PCR on DHI samples

Ilka Klaas. University of Copenhagen, Denmark

PCR is a technique that can diagnose mastitis pathogens with a high specificity and sensitivity. There have been previous concerns of carry-over and contamination of samples between cows. DHI samples are taken during milking and there is usually no disinfection step of the milking equipment between two cows.

In this investigation from all cows, a PCR sample was taken from normal DHI recording samples. A aseptic foremilk sample was taken from cows at every other milking unit.

The statistical analysis showed that cows being milked after a S. aureus were more likely to have a PCR positive sample. This indicates that carry-over between samples happens. Teat preparation including teat disinfection reduced the contamination and should therefore be advised while taking samples for PCR. Also the order in which cows were sampled, as well as other inflammatory signs (SCC) should be taken into account while interpreting the results.

Topical treatment of udder cleft dermatitis

Tine van Werven. University of Utrecht, The Netherlands

Udder cleft dermatitis is a fairly newly described disease. It considers skin lesions between the two front quarters or between the quarters and the abdominal wall. It affects highly producing dairy cows and has a very severe chronic aspect. The etiology remains unknown, but has been linked to bedding material and digital dermatitis.

In this experiment two topical treatments were investigated. The first treatment included a wipe to protect the healing wound from dust. This was only used for mild and moderate cases. The severe cases were daily treated with an enzymatic wound healing product. Both treatments were compared to a negative control, since no treatment for this disease has been validated yet.

206 cases were enrolled in the study, of which 113 mild, 47 moderate and 43 severe. The treatment for mild cases did not inrease cure. In the severe cases, there was a better cure and improved wound healing.


Mastitis Control Programmes Session; Monday 4th July

Keynote: The role of veterinarians in mastitis management

Pamela Ruegg. University of Wisconsin, US

Pamela Ruegg opened her talk with the request to at least implement on one thing after her talk.

During the past decade, the industry has seen dramatic changes: somatic cell count declined and milk production per cow dramatically increased. Herd size tripled, while number of herds has been reduced, not only in the US. The trend to larger dairy farms is accelerating globally. There is a trend to come to one global similar production system. The impact of these changes influences what we as vets are able to do. The management of large dairy farms is diverse compared to small family farms: there are fewer workers per cow and those workers are highly specialized. A calf pen worker is working on obstetrical procedures on multiple cows per day, while in a 60 cow dairy only one cow per week gives birth.This new management requires more metrics, data, analysis, expert systems, while there is no such an expert system found that could replace a skillful cow person.

Therefore, what are the challenges veterinarians face in evolving to a slightly different role? The historical role of the vet such as depicted in the James Herriot books, appealed a lot of interest of young kids subsequently applying to vet school. Until 1970 that was the role of the vet: he was mainly focused on the treatment of sick cows.

In the 80´s herd health programs were the focus. But they were reproduction programmes, they were focused on palpating to ensure reproduction success of the herd. Vets haven’t been engaged as much in proactively managing udder health on many farms. Yet it is the only disease that directly alters the secreting gland, influences reproduction, reduces value of the milk, probability to be culled. It also highly defines antibiotic use, which increasingly becomes important.

Some surveys in the US, UK and in the Netherlands proved that most vets do not work with ANY farms in mastitis control. It also does not seem to be the farmers priority and farmers believed that vets were either not aware or ignored their herd health goals.

Barriers to implementation of udder health programmes are to some extend similar as those to implement reproduction programmes: lack of demand from the farmer, vets do not feel confident or competent enough... Some vets are feel all alone and do not want to be engaged with the farm workers. It seems that vets have other ways of income that take up our time an provides income. Some barriers to engagement are different than those for reproduction programmes. Udder health doesn't include only the vet: it involves equipment, housing issues, choices of bedding. These have other advisors on farm that have specific knowledge. Engaging with those advisors is key, yet they have an advantage over the vet: they are selling something and do not require compensation for their time.

Personality type of the vet also plays a role. Vets tend to be people who overemphasize a knowledge based, practical approach of the world. We underestimate social skills and intuitive approach, unlike sales people. We are making our profession vulnerable by limiting our role to reproduction visits, which is a role that can easily be replaced by training technical people on the larger scaled dairy farms. Vets have to dismiss the “clinical role” they play and develop problem solving skills.

When vets are told they should increase their role on dairy farms, they think of monitoring, house design, scoring, bacteriological culturing and training people usually comes up. Vets, however, should not forget to come back to the basis: developing, implementing and evaluating mastitis treatment protocols. Being responsible in antibiotics is globally a top priority. We have to understand these concerns. Vets are the only farm professionals that have the ability to develop protocols and there is plenty of room for improvement. The two most common drugs for treating mastitis in the US are cefapirin and ceftiofur. Ceftiofur has the advantage of a very appealing label because it offers flexibility. Yet it is hard to justify to treat mastitis with such a drug, especially since many mastitis cases are culture negative

Local vets should develop and assess protocols. Cows should be examined before antibiotics are used. There should be a reasonable belief that bacteria are present. Narrow spectrum should be the 1st choice and duration should be as short as possible to result in effective cure. There is a need to define a treatment team. The milking technicians should consistently do a pre-milking routine and identify clinical mastitis. When mastitis is suspected, they should collect an aseptically taken sample. Treatment however should not be performed by the milkers during milking process, yet by the owner or herdsperson who should consider cow history and examine the cow before treatment. Besides treatment, watchful waiting, drying off the gland or culling should be considered equally. The vet should be the leader. He should develop and supervise protocols and monitor outcomes. He should check whether antibiotics are used only on cases that benefit and how chronic cases are managed. He should advise on the appropriate duration of treatment and change of treatments. Success should be defined and judged.


Attitudes of Dutch vets towards the use of AB in dairy cows

Christian Scherpezeel. GD, The Netherlands

In the Netherlands preventive use of antibiotics is no longer permitted. Moreover, reduction of dry cow therapy (DCT) could help to reduce the overall use of antibiotics.

Dry cow therapy is now only allowed in the Netherlands in cows with intramammary infection. Selective DCT became obligatory in 2013 and the guideline was implemented in 2014. Since the mindset and attitude of farmers and vets is very important in the success of such legislation, the presented survey was carried out.

Questionnaires were sent out to all Dutch bovine vets in March 2015, asking on how they felt about the new policy. Questions were included on what their thoughts were on how farmers would react, what their attitude to antibiotic use in general was and more specific on selective dry cow therapy.

Both vets and farmers found reduction of antibiotics important. Vets however underestimated the positive opinion and active implementation of the guideline of farmers. 75% of farmers already implemented the guideline, while vets estimated that would be only 37%. Vets saw themselves mainly as a technical advisor in the policy, with only a minority feeling that they were the messenger of bad news. The majority spoke positively of the changes and felt that they were on the right path.

Anti-Microbial Resistance Session; Wednesday 6th July

Developing a practice based approach to antibiotic use on farm

David Barrett. University of Bristol, UK (Speaking for Tisdall)

The speaker explained how the University ambulatory practice changed the policy for using antibiotics to restricting the use of critical antibiotics such as 3rd and 4th generation cephalosporines, fluoroquinolones and long acting macrolides.

It seems that farmers are not resistant to change. Once vets are on board, the farmers engaged very swiftly. “ I do not think that we need fluoroquinolones in dairy practice” David Barrett said. They exchanged all the intramammary 3rd and 4th generation cephalosporines for penicillins and aminoglycoside combinations. Also systemically administered 3rd generation cephalosporine was subsituted with penicillin or a 1st generation cephalosporine.

The change was guided by an iterative process of changing policy and implementing responsible use, improving animal health and evaluation. As a result of the policy, critical antibiotic use dropped massively. “This proves we can do this and that we can do it in UK practice. The cows are still healthy and productive.” He also emphasised that we need to choose the right dose for the right animal and the right drug. Therefore measuring the amount used and put limits on volumes used is not such a good idea.

He concluded with the inspiring quote” Nobody made a greater mistake than he who did nothing because he can only do a little”.

Are resistant bacteria in raw milk a “One Health” issue?

Bernd-Alois Tenhagen. Federal Institute for Risk Assessment, Germany

There is an issue with resistant bacteria in both animals and humans. Bacteria do not restrict themselves to either humans or animals, so we must be concerned about transmitting resistant bacteria or resistant genes. Especially vets and farmers should be careful and consider resistant bacteria a possible occupational disease.

With therapeutics we aim to kill the pathogen, but we also affect the gut and skin flora. After intramammary treatment, the amount that reaches the gut flora is less relevant, unless we use waste milk in calves. In addition, dairy cows are relatively infrequently treated with antimicrobials in comparison to other food producing animals such as veal, pork and poultry.

The real “One Health” issue of the dairy industry in Germany is the use of 3rd and 4th generation cephalosporines and fluoroquinolones. These are relevant for humans as well. So volume of antibiotics in cows used is low, but share of critically important ones is very high.

The researchers set up a monitoring system, checking susceptibility of bacteria in bulk milk and environment in German herds. The monitoring is repeated every 3 years and since 2014, organic herds are included as well (as a separate group) . Resistance is tested with broth microdilution.

In previous years, MRSA was found in 4 to 5% of bulk milk samples. It was also found in farm staff with very high detection rates amongst workers in the veal industry. Regional differences in prevalence of MRSA are present, typically higher in areas with a high pig density. In the 2014 monitoring, the prevalence of MRSA doubled compared to before: 1 in 10 conventional herds tested positive for MRSA. The MRSA strains were often carrying several other resistance mechanisms, such as against tetracyclines, streptomycin etcetera. Anecdotally, bacteriological labs reported that more isolated from mastitis cases were diagnosed with MRSA.

E.coli resistance

Resistance against E.coli in the dairy food chain is minimal compared to other sectors. In poultry industry (both in retail as on the farms), more resistant strains are found than susceptible ones.

The monitoring investigation performed in 2014 described above, registered a slight increase in susceptible strains from 2008 to 2014. The researchers concluded that E.coli resistance is currently not a major concern in bulk milk in Germany.

National Cattle Health Programmes Session, Thursday 7th July 

AMR benchmarking in NZ

Mark Bryan, New Zealand. Chair AMR group of NZ Vet Association

The New Zealand Veterinary Association (NZVA) has recently set an aspirational goal of using zero antimicrobials for the maintenance of animal health and welfare by 2030. As a veterinary profession, the last thing we wanted to do was to be mandated by politicians. We absolutely need to retain the right to use antibiotic for treatment. Surprisingly, farmers are further along this journey than vets. Farmers see antibiotic use as a cost; veterinarians are much more difficult to convince about the need to change their behaviour.

A key issue is measuring antimicrobial use. You can do this in volume or kilograms sold, but that is a very crude measure, while the calculation of ADD (Average Daily Dose) and ADUR (antimicrobial drug usage rate) are not very coherent between Europe, North America and New Zealand.

In this study, which was established to benchmark the antimicrobial use between farmers, PCU (population corrected unit) was used. On PCU level, New Zealand has a very low level of antimicrobial use, comparable to low using countries like Norway. Besides, it is the fact that the vast majority of products used in New Zealand are penicillins. Regional variations exist, in both volume and kind of antibiotic used. Half of the used antimicrobials are injectable and another large percentage is used as dry cow therapy (DCT). On the latter, the industry is severely challenged by the public and politicians. Lay people do not understand the concept; it goes against their logical approach. 66% of cows get routinely DCT, a percentage that did not change over the last years.

Although improvement is probably still possible, the results indicate that New Zealand is doing comparatively well in the dairy industry. This stands in contrast with the medical profession, where New Zealand is actually one of the highest users of antibiotics worldwide.

Mark Bryan concluded that it is very important for the veterinary profession to lead this space and that it does not become a political game. The Dutch have responded remarkably to the approach from politicians. Farmers are ready to use fewer antibiotics or dry cow therapy. The profession has to move along. Prudent use is not a single species issue, it is a “One Health” issue.

Policytakers to policymakers

Kristen Reyher. University of Bristol, UK

In the UK, a political mandate to reduce antibiotics in agriculture is not existing. Retailers and milk processors are starting to write guidelines and set targets. Whether these targets are based on science or not, the approach is usually very top down. Bristol University was approached by milk buyers to be involved in the making of their policy and they decided to let the farmers define themselves what they can do to improve the responsible use of antibioics.

They started with four regional workshops around responsible use. The buy-in from farmers was larger than expected, more farmers got to this meeting than for any other educational meeting. The meetings started off with a presentation supprted by an audience response system. Afterwards vets and farmers talked separately in focus groups and they were asked to define actions they could take and prioritise those actions. The researchers evaluated and analysed the data gathered in the workshops and made a draft formulary that was then presented back to the farmers to give them the chance to make adaptations.

The conclusion from this unusual approach was that farmers do think responsible use is an important topic. 79% of them agreed that antibiotic use is too high. Approximately 40% thought they had themselves a more mild or moderate use of antibiotics, although the large majority did agree they could reduce, especially for critical important antibiotics.

The bottom up approach of policy making helps to improve sustainable farm practice. The changes they suggested are achievable, practical and increase the buy-in for improvement.

Images courtesy of WBC 2016 press service.

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