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Canadian Bovine Mastitis Research Network

All about Mastitis I Management / Prevention

Herd Visit I Formulating a Plan I Follow-up

How Can I Solve a High Somatic Cell Count Problem? 

Last month, after you read the first part of this article, you rolled up your sleeves, called the vetenarian and started working on defining the problem of high SCC in your herd. Once this is done, a herd visit needs to be organized with your veterinarian.

 Herd Visit

The visit consists of three elements: tour of the farm, observation of milking practices, and sitting down together. It is essential that the owner, the herdspersons and the veterinarian are involved in all 3 components, otherwise buy-in and implementation of changes will not happen. Often, other people have already been involved and some strategies have already been implemented to remedy the problem. An inventory of what has been done by whom, and what effect this has had, is important. If it is clear that the milking machine or nutrition may play a role, the concerned experts should be involved.

1- Farm Tour
Even if the farm is visited on a regular basis in a herd health program, a farm tour with focus on udder health risk factors is necessary. Existing data collection forms can be used to ensure that no points are overlooked.
2- Milking
Before milking starts, the milking parlor is observed and the milking machine is examined (e.g. type, cleanliness, presence of automatic take-offs). When was the milking machine last serviced and how frequently is it done? Often the tractor or the new truck receive more maintenance than the milking machine….

During milking, the following is monitored:
  1. actual milking practices and milking hygiene;
  2. general impression of the functioning of the milking machine; and
  3. behavior of the cows during milking. Important points to pay attention to during milking are:
  • Does the milking routine consist of udder stimulation, pre-stripping, pre-milking teat disinfection, a 60 to 90 second interval between udder stimulation and attachment, timely take-off (automatic or not), and post-milking teat disinfection? If there is an indication that intervals between pre-milking treatments and attachments or between milk-out and detachment are irregular or long, a time-study should be performed.
  • What is the number of cows per towel?
  • What is the hygiene during milking?
  • Do the milkers wear gloves?
  • Are all teats well covered with post-milking teat disinfectant?
  • What is the milking order for pens or cows with known SCC or infection status?
  • When are cows with clinical mastitis /high SCC/known bacteriological status milked, and what is done with the milking equipment after milking them?
  • What is the condition of the teats after milking (color and hyperkeratosis)?
  • What is the frequency of liner slips and falling teat cups?
  • Are the cows at ease during milking? After milking, the status of the milk filter should be checked for milking hygiene or failure to detect clinical mastitis.
3- Sitting Down
When the farm tour and milking have been completed, everybody involved must sit down, review and complete the history, define the problem, state realistic short-term and long-term goals, and develop an intervention plan. In addition to the observations made at the farm tour and during milking, the status of the following topics needs to be discussed:
  • Treatments: clinical mastitis, subclinical mastitis, and dry cow therapy. On most dairy farms, a (too high) variety of treatments is used for clinical mastitis. It is advisable to agree on a herd-specific treatment protocol for clinical mastitis, based on knowledge of the most common causative agents of clinical mastitis on a farm. High bulk tank SCC is often associated with high percentage of subclinical mastitis and treatment of cows with subclinical mastitis should also be considered. This strategy is often successful in herds where Strep. agalactiae is the main cause of mastitis, but it can also be considered in herds with mastitis caused by other streptococci or Staphylococcus aureus. Blanket dry cow therapy is essential in herds with a high bulk tank SCC. It is, however, practised on only 75% of dairy farms in Canada.
  • Culling and availability of replacements. Culling of high SCC cows has an immediate effect on the percentage of cows with a high SCC and results in a decrease of bulk tank SCC. Additionally, the number of new cases of contagious mastitis is predominantly determined by the number of infected cows present in the herd. The more that cows shed bacteria into towels, teat cup liners, and hands of milkers, the more likely it is that additional cows will become infected. Realize that the implementation of measures that decrease the rate of new infections, such as post-milking teat disinfection, will not immediately lower the bulk tank SCC. However, this decrease will only occur if culling or cure decreases the number of existing high SCC cases. Availability of sufficient young stock to replace culled cows is a prerequisite for culling. If 50% of calves born are heifers, if the large majority of the calves is not sold, and if calf mortality is not too high, approximately 25% of cows can be culled on a yearly basis. This is, however, the average culling rate of a non-problem herd. To overcome a high bulk tank SCC problem, the culling rate, and the number of young stock available, may need to be increased. The feasibility of such increases will depend on other management and health aspects, e.g. herd fertility, participation in disease eradication programs, and involuntary culling due to disease in young stock or cows. Of course, the quota situation also influences short-term culling decisions. 
  • Nutrition. In addition to the level of exposure, resistance to infection determines the number of new infections. Nutrition is an important factor in this, and it is too often forgotten when dealing with a Staph. aureus problem. Specifically address supplementation with minerals such as selenium, particularly of the pregnant heifers and the dry cows.
Formulating a plan
The intervention plan should be divided into practices that will achieve the following: 
  1. decrease the percentage of new infections;
  2. decrease the duration of infection; and/or
  3. decrease the incidence of clinical mastitis. The management style and the situation on the farm (e.g. expansion plans, shortage of young stock, milk quota situation, financial situation, management characteristics of the farmer) should be kept in mind when deciding on a realistic time line and goals for intervention. Do not try to change everything at once.

Recommendations should be prioritized using the following 3 criteria:

  1. ease of implementation;
  2. effect of the change; and
  3. cost of the recommendation. Highest on the list will be cheap recommendations that are easy to implement and have a large effect. Examples include the use of post-milking teat disinfection to reduce the percentage of new infections and the culling of chronically infected animals to decrease the duration of infection and lower the bulk tank SCC. On most farms, no more than 5 changes should be made. Otherwise, possibly none of the recommendations may be implemented because everybody is overwhelmed. The success of interventions depends heavily on the motivation of the farmer and whether he/she applies control measures rigorosly.

A high SCC problem cannot be solved with one visit. The adoption of recommendations and their effect needs to be checked. Consistent attention from veterinarians or herd advisors to udder health management has repeatedly been shown to contribute to improvement of the situation. Therefore, more visits when sufficient new data are available is needed. If the situation changes, adjustment of goals and plans may be necessary.

Stay in touch with the veterinarian and contact him/her when new bulk tank SCC data, DHI records, or culture results are available. Preventing a recurrence is important. When the short-term goal is met, often not enough priority is given to the agreements anymore and achievement of long-term goals falls by the wayside.

Herman W. Barkema1, Sarne De Vliegher2, Julie Baillargeon3, and Ruth N. Zadoks4.

1Veterinarian, Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary.
2Veterinarian, Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Belgium.
3Agronome, Agente de transfert, Réseau canadien de recherche sur la mammite bovine.
4Veterinarian, Division of Veterinary Clinical Studies, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Veterinary Centre, Roslin, and Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Scotland, UK.


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