Effective mastitis control reduces sub clinical and clinical mastitis rates based on lowering new infection rates. Such a sustainable improvement of udder health reflects on social needs, as well as on economic aspects of modern animal health management. Among German dairy herd production disorders, mastitis is responsible for the largest disease-related economic losses. This is due to its prevalent character. In addition, the largest share of antibiotic consumption on a farm arises from this infection.
Dairy farmers perceive increasing mastitis problems differently and in order to mitigate a mastitis problem, herd-individual approaches are mandatory. All approaches are connected to new decisions and to attitude changes. Works on communication in udder health found that attitude changes in farmers and veterinarians are dependent on different aspects, including rules and regulations, education, social pressure, economics and tools. Effective programmes should focus on all of these aspects. A good mastitis control concept should start (and follow up) with a systematic herd analysis, based on milk recording data and/or clinical mastitis data, cytomicrobiological outcomes and the analysis of standard operating procedures: breeding, housing, feeding, milking, culling and treating. Also important is the availability of reliable data and science-based interpretation. Based on this, farmers and vets can develop farm-specific objectives and will be able to monitor progress. These ideas brought us to the development of some simple science-based tools that attempt to reflect on most aspects.
We started four years ago with a larger transfer project in Germany called “milchQplus” (Healthy udders for sustainable milk production). The umbrella organisation of the dairy herd improvement organisations in Germany, the largest dairy herd improvement laboratory and the microbiology group of the University of Applied Sciences Hannover worked together on this project.
Currently, 48,000 farms make use of the dairy herd improvement service. Some 3.7 million animals – or 90 per cent of all cows in Germany – are recorded under the project. The aim of the project is to help practitioners make evidence-based therapy and management decisions that reduce the prevalence and incidence of mastitis by introducing and using indicator figures based on milk control results.
Key figures for mastitis control
For this project, we used dairy herd improvement data to improve three important aspects, communication, complexity and continuity in the daily routine. Stated key figures of udder health at farm level are not only a help for experts, but they also serve as an objective basis of communication between farmers, consultants and veterinarians to identify actual problems (udder health bottle-necks) in an ongoing manner.
Four years later, the project is completed, and the key figures can be found for every farm in the dairy herd improvement reports (Table 1). Due to the federal structure in Germany, key figures are presented differently in the individual federal states (online, printed, etc.). However, the calculation is carried out in all federal states according to the same principle based on a common guideline. For the first time it is possible to make dairy farms, regions and countries comparable with regard to the subclinical udder health situation. So far, Germany-wide data on the key figures have been published once (Table 2). Udder health specialists, veterinarians and agricultural advisors use the data.
Tabel 1 The key figures in milchQplus
1. Proportion of “udder-healthy” animals: The first key figure is the proportion of “udder-healthy” lactating animals (< 100,000 somatic cells/ml in last dairy herd improvement sampling) on all lactating animals in a herd. This “global” key figure indicates if udder health problems exist and if the udder health should be taken into focus by the herd manager and the veterinarian. Farms with a good to very good udder health reach a value of app. 70% of “udder-healthy” animals.
2. Proportion of incurable animals suffering from mastitis: This key figure is the proportion of incurable animals suffering from mastitis (3 x > 700,000 somatic cells/ml) on all lactating animals. This figure should be as low as possible. The value should be < 1%. However, since a long-life span of the animals is a goal, a balance between culling and productive life span has to be found on the base of this key figure.
3. New infection rate in lactation: This figure is the proportion of animals with > 100,000 somatic cells/ml in the last dairy herd improvement testing and ≤ 100.000 somatic cells/ml in the previous dairy herd improvement testing on all animals with ≤ 100.000 somatic cells/ml in the previous dairy herd improvement testing. Good farms reach a value of at most 11%. This figure allows the evaluation of the quality of cleanliness, hygiene, husbandry and milking procedures.
Two key figures help to evaluate the effects of the dry period on udder health and one to evaluate the udder health in fresh heifers.
4. New infection rate in dry period: This figure is the proportion of animals with ≤ 100,000 cells/ml in the last dairy herd improvement testing before drying-off and > 100,000 cells/ml in the first dairy herd improvement testing after calving on all dried-off animals with ≤ 100.000 cells/ml in the last dairy herd improvement testing before drying-off. Good farms reach a value of at most 15%.
5. Cure rate in dry period: This figure is the proportion of animals with > 100,000 cells/ml in the last dairy herd improvement testing before drying-off and ≤ 100,000 cells/ml in the first dairy herd improvement testing after calving in all dried-off animals with > 100.000 cells/ml in the last dairy herd improvement testing before drying-off. In good farms the value should be higher than 70%.
6. Heifer mastitis rate: This figure indicates the importance of heifer mastitis in a herd. It is the proportion of heifers with > 100.000 cells/ml in the first dairy herd improvement testing on
all heifers. Best farms have a heifer mastitis rate of at most 18%.
Table 2: Comparison of the average key figure numbers of Germany and single dairy herd improvement organisations (2015)
|Dairy herd improvement organisation||Number of controlled animals||Proportion of “udder healthy” animals (key figure 1)||Proportion of incurable animals suffering from mastitis (key figure 2)||New infection rate in lactation (key figure3)||New infection rate in dry period (key figure 4)||Cure rate in dry period (key figure 5)||Heifer mastitis rate (key figure 6)|
In the meantime, some scientific work has been carried out on these indicators and the values determined in German farms. At the individual farm level, use depends very much on the importance of the udder health situation for the farm. In a survey of 499 dairy farms across Germany, 58 per cent of farm managers state they systematically use the new indicators in their udder health work.
In a current project with the “Landesvereinigung der Milchwirtschaft Niedersachsen e.V.” to improve udder health and reduce the number of bulk milk somatic cell count in dairy herds in Lower Saxony, we are working on the implementation of indicators in the daily udder health work on our largest dairy farms in Lower Saxony.
Another aspect of the milchQplus program is to improve the practical transfer of knowledge. Many one-sided leaflets have been created that deal with scientific findings on partial questions of udder health (e.g. teat condition, milking, milking speed, Staphylococcus aureus control, etc.) in a practical manner. For every leaflet the content of one scientific paper was used to answer a practical question.
Since the evaluation of the indicators showed that the udder health of dairy herds in Germany is burdened by too many animals that are chronically ill and incurable, it was only logical to work on scientific criteria for better culling decisions in the next step. Due to the ongoing public discussion about the life span of dairy cows in Germany and the breeding commitment of many dairy farms, German dairy farmers try to avoid culling.
Scoring system for better culling decisions
Various health disorders such as impaired reproductive capacity, lameness, milk fever, displaced abomasum as well as insufficient udder health are known as risk factors for removal of affected cows from a dairy herd. The cure of mastitis can be difficult or impossible. Mastitis as an infective disease is of particular importance as every infected cow can increase the risk of udder disease for the entire herd. This means that depending on the pathogen found, prevention for the remaining cows also has to be taken into account before making the decision to cull a cow. Therefore, it can be concluded that any cow with little or no prospect of bacteriological cure should be removed as quickly as possible from the herd. An objective evaluation of probability of cure before implementing therapy could help reduce the use of antibiotics. For this purpose, it is essential to establish a clear definition of cure, parameters affecting cure, and subsequent rationality of antibiotic treatment. In various publications, the term ’cure’ connotes bacteriological cure. Bacteriological cure implies that microorganisms detected before treatment are not found afterwards.
Animal- and pathogen-related factors are generally considered to influence bacteriological cure. Older animals or cows with a higher number of lactations have lower chances of cure than a younger cow; therefore, age is an important influencing factor. Current somatic cell count (SCC) influences bacteriological cure – the higher the SCC, the lower the chance of cure. Furthermore, the animal’s SCC history during the previous months, as well as its mastitis history (clinical mastitis during the current and previous lactation indicates lower chances of cure) are described as influencing factors for bacteriological cure. Apart from clinical mastitis history, the above-mentioned animal-specific factors are available on 88 per cent of all German dairy farms as part of dairy herd improvement data. The number of clinical mastitis cases in current lactation, milk yield and the individual sum 200-7 were found to be significant animal-related factors to the declining chance of bacteriological cure. The individual sum 200-7 was calculated by cow somatic cell counts (CSCC´s) of seven months before moment of decision for or against culling. It is a calculated sum making a statement about the CSCC history with a higher weighting of CSCC closer to the point of decision. For the individual sum-200-7, a threshold of 200,000 cells/ml was used. For those exceeding the threshold of CSCC directly before clinical mastitis, the summand was 7, this amount diminishing each subsequent month before the point of decision. Therefore, an excess of CSCC two dairy herd improvement recordings before the moment of decision was given the summand 6 and so on. CSCC with the highest distance to moment of decision (seven dairy herd improvement recordings before) was given summand 1 in the case of threshold exceedance). The seven summands were added up and a sum from 0 to 28 could be expected, which is utilized in the scoring system (Table 3). The scoring system has been developed taking into account scientific knowledge and the available information to predict the curability of mastitis (Table 3). Thus, even without an absolute limit for the culling decision, a comparison of animals can be made. Implementation of the system into a herd management concept can help to avoid antibiotic treatment where there is no further benefit for the cow and reduce the number of incurable animals suffering from mastitis, which may be a source of udder pathogens. The scoring system can be easily adapted for individual herd monitoring concepts by omitting individual influencing factors, which cannot be detected or can only be recorded with considerable additional effort.
Table 2: Scoring system including influence factors and weighting of their manifestations for the evaluation of the animal-related probability of bacteriological cure
|Age (lactation number)||1||2||>2|
|Mastitis during current lactation (number of clinical cases)||0||1||>1|
|At least 1 clinical mastitis case in previous lactation||No||Yes||–|
|SCC† in last dairy herd improvement report before mastitis (x 1000 cells/ml)||< 400||400–1000||>1000|
In the unfortunately still numerous dairy farms without documentation of clinical cases of mastitis, we recommend the removal of animals, which in the last three milk controls each reached more than 700,000 cells/ml in individual milking. Alternatively, the permanent drying of such udder quarters is also possible.
Evidence-based mastitis management
Following the social demand for minimizing the use of antimicrobials in livestock farming, we have turned to evidence-based mastitis therapy in further projects.
The current status of scientific literature on therapy of clinical mastitis emphasizes that by far not every mastitis case requires antimicrobial use. However, mastitis therapy should always comprise the initial systemic application of a non-steroidal anti-inflammatory drug, independent of the mastitis-causing pathogen or mastitis grade. On the contrary, antimicrobial therapy decision is based on the mastitis-causing pathogens, the clinical grade and individual animal status. In general, local antimicrobial therapy should be administered in mild and moderate mastitis cases, while the antimicrobial treatment success is questionable for mastitis-causing pathogens other than streptococci and staphylococci. Severe cases of mastitis, which appear with systemic illness of the cow, always require systemic antibiotic therapy. Studies on an extended duration of intramammary antimicrobial treatment beyond that prescribed by the manufacturers´ instructions indicate benefits for infections caused by streptococci and acute S. aureus infections. Decisions on extended therapy should therefore not be made before microbiological results are available. Narrow-spectrum ß-lactam antibiotics are the antimicrobial agents of choice for local treatment of intramammary infection caused by streptococci and staphylococci.
Evidence-based mastitis therapy implies the systematic implementation of diagnostic systems, which enable a respective differentiation of mastitis causing pathogens. Reliable presumptive pathogen-group identification and avoidance of subsequent adverse consequences for animal welfare therefore require suitable test systems.
Commercially available test systems are easy to perform and yet provide valid results within 12 hours of incubation. The identification of the pathogen groups presents guidelines for treatment decisions, although they cannot replace proper microbiological culture. Rapid on-farm test systems, such as the combination of two PetrifilmTM (3M) plates (Rapid Aerobic and Rapid Coliform Count) enable the discrimination of pathogen groups and provide results within 12 hours (“Gram-positive”, “Gram-negative”, “no growth”). We have developed another validated rapid-test system called mastDecide®, which provides respective results, stands out as a very easily and safely applicable tube test system (Picture 1).
The implementation of such simple test systems enables the accomplishment of evidence-based concepts in clinical mastitis therapy. The use of such test systems requires careful handling.
Selective Dry Cow Treatment
In selective dry cow therapy (sDCT), methods for identifying cows with an intramammary infection at dry-off are necessary (e.g. bacteriology, raised somatic cell count, clinical mastitis in previous and ongoing lactation, positive California mastitis test (CMT) at drying off). All udder quarters of an eligible cow should be treated with antibiotics to achieve similar results with selective as with general dry cow therapy. According to the Commission notice (2015/C 299/04), the systematic treatment of cows at drying-off should be avoided. It should be applied in a way with considering and implementing alternative measures on a case-by-case basis.
Even if sDCT is mandatorily performed, infected cows should not be left untreated. Thus, the criteria for accurately identifying infected cows to receive treatment at dry-off need to be improved to enhance the accuracy of the sDCT.
Logistic and financial considerations involved in sampling and examining (cyto-bacteriological) milk from all cows usually make this selection method impractical. The most commonly used selection method is based on the monthly-recorded cow SCC. Furthermore, the CMT at dry-off and the CM history of the cow are mentioned as selection tools. Decision schemes with similar outcomes compared to bacteriology as a key indicator for intramammary infection at dry-off were shown based on SCC from dairy herd improvement data combined with CMT testing. In a recent study, intramammary infection at dry-off were most accurately identified using a geometric mean SCC of 100,000 cells/mL as a threshold at either one or three dairy herd improvement records prior to dry-off. Using a combination of SCC with either CM history, CMT at dry off or parity slightly increased the sensitivity of detection. The probability of cure of the infection over the dry period increased with use of both antibiotic DCT and application of an internal teat sealant (ITS), and decreased when the dry period was longer than 56 days.
In another study the use of SCC and aerobic bacterial counts as possible tools to choose cows for sDCT were investigated. Animals chosen for the investigations were divided up into three study groups and all quarters were treated with an ITS, no matter which group they belonged to. This study revealed that control group C, in which all cows received an antibiotic DCT, achieved the best results regarding udder health. However, the results of the two study groups A (Aerobic Count Petrifilm™ group) and S (SCC group), in which the animals were dried off selectively, were only marginally worse [6 (S) and 3 (A) % lower cure rate and 2 (S) and 1 (A) % higher new infection rate on quarter level]. Furthermore, it was shown that the lactation number, as well as the microorganisms present at the time of drying off, influences udder health.
Even if infected cows are identified correctly, several factors influence the probability of cure in treated cows and animals with low healing prospects, should rather be recommended for culling.
A systematical veterinary supervision of udder health in dairy farms is a precondition to avoid critical situations and to aid in continuous improvement. Monitoring of the most important key figures, risk factor analysis when needed, clear decision rules for diagnostics, culling and treatment and the continuous development of this system should help to understand and improve udder health. It is a precondition for prudent antibiotic use. Complex strategies need tools to ease the necessary work on a regular base. The implementation of these tools depends on the willingness of all involved parties. Some farmers do not have a particular interest in the professionalization of mastitis control. However, the best farms are not managed by crisis intervention strategies, but by continuously improved strategies.
References Degen S, Knorr N, Paduch J-H, Klocke D, Zoche-Golob V, Hoedemaker M, Krömker V (2015): Cell differentiation assisting in evaluating mastitis treatment prognosis. Milchwissenschaft 68: 2-9 Kiesner K, Wente N, Volling O, Krömker V (2016): Selection of cows for treatment at dry-off on organic dairy farms. J Dairy Research 11/2016; 83(04). DOI:10.1017/S00220299160006622016 Krömker V, Leimbach S (2017): Mastitis treatment - Reduction in antibiotic usage in dairy cows. Reprod Dom Anim.; 52 (Suppl. 3): 1–9. Tho Seeth M, Wente N, Paduch JH, Klocke D, Mansion-de Vries E Hoedemaker M, Krömker V (2017): Different selective dry cow therapy concepts compared to blanket antibiotic dry cow treatment. Tierärztliche Praxis; 45(06): 343-349 Ziesch M, Krömker V (2016): Factors influencing bacteriological cure after antibiotic therapy of clinical mastitis. Milchwissenschaft 69, 7-14
Text: Volker Krömker (Volker.Kroemker@hs-hannover.de), Doris Klocke, Jan-Hendrik Paduch, Nicole Wente, Yanchao Zhang, Stefanie Leimbach University of Applied Sciences and Arts, Fac. II, Bioprocess engineering - Microbiology