Quick facts
- Mastitis is one of the costliest diseases on dairy farms.
- A dairy farm can lose profit through decreased milk yield, treatment costs, discarded milk, premature culling and death, decreased genetic potential and decreased reproductive performance.
- Maintaining a low somatic cell count (SCC) takes diligence and focus by everyone on the farm.
- Forming a team of the farm owners, herd veterinarian, key employees and other milk quality experts is key to achieving a consistently low SCC and clinical mastitis rate.
Mastitis is one of the costliest diseases on dairy farms. A dairy farm can lose profit through decreased milk yield, treatment costs, discarded milk, premature culling and death, decreased genetic potential and decreased reproductive performance.
The Mastitis Problem Solving spreadsheets can help estimate annual losses due to mastitis on a specific dairy and contain tools that will help you to troubleshoot and develop a plan of attack.
Trying to reduce somatic cell count (SCC) through treatment and culling strategies alone is frustrating and often futile. Unless you can identify the root cause of why cows are being infected, new cows will become infected and SCC will increase.
Develop a plan
A well thought out prevention and control plan will keep SCC low. Often the best approach to reduce SCC and clinical mastitis is to form a milk quality team. Include on your team your veterinarian, key employees, dairy plant field representative, dairy equipment personnel, Extension personnel, and others you think might be helpful.
Develop a plan for reducing your SCC based on your farm’s information.
Systematically following the steps listed below will result in a faster resolution of a high SCC with less frustration.
Define the problem and identify the organisms
The first step is to identify the major organism(s) causing mastitis on the dairy. The University of Minnesota Laboratory for Udder Health has factsheets with more details on mastitis pathogens. Identifying whether the main mastitis pathogens are contagious or environmental will help focus the next steps in your investigation.
- Use bulk tank cultures to screen the herd for contagious mastitis pathogens and to determine if cow prep is adequate. You will need multiple bulk tank cultures to rule out contagious organisms.
- Culture the most recent 10-30 mastitis cases to determine what is causing clinical mastitis on your dairy.
- You must sample milk before administering any treatments.
- Individual samples can be frozen and submitted for culture later (within 1 month).
- You may want to culture some cows with SCC over 200,000 cells/ml for 2 or more months to determine what pathogens are causing chronic, subclinical mastitis on the dairy.
Use DHIA and clinical mastitis records to investigate which group of cows are becoming infected.
- Are high SCC cows predominantly new infections or cows that have been infected for several consecutive months?
- Heifers or older cows?
- Fresh or mid-lactation cows?
- Certain groups or pens?
Investigate why cows have high SCC and are getting infected
You can use tools like the “Fishbone Diagram” and “5 Why’s” worksheets on the Roadmap to mastitis problem solving spreadsheet to help identify potential reasons why cows are getting infected.
Knowing whether the main cause of mastitis is contagious or environmental will help focus your investigation, as these types of pathogens have different sources and means of spread on the dairy.
Mastitis problems can have multiple facets. It is often a relationship between cow health, herd environment and management. Consider how overall cow health might be contributing. Cows with compromised immune systems are more susceptible to mastitis infections.
Based on your investigation, generate potential solutions in an action plan that will work within the herd’s management system. There are three important stages of action planning:
Step 1: Develop an action plan
Action plans should address the highest impact issues identified in the investigation, starting with the least costly interventions. Action plans should be specific, written, and should identify a person responsible for each item and a deadline for when it will be completed.
If a change in routine is required, initiate a training program. Employees will be more likely to follow through with implementation if they participate in creating the action plan
Here are general guidelines on plans for different categories of organisms.
Contagious organisms (Streptococcus agalactiae, Staphylococcus aureus, Mycoplasma spp.)
Contagious organisms are well adapted to survive inside the mammary gland. Contagious organisms spread to new cows during the milking process. Control of contagious organisms includes the following:
- Identify and treat, segregate or cull infected cows.
- Strep agalactiae responds well to treatment.
- S. aureus and Mycoplasma do not respond well to treatment.
- If possible, segregate positive cows and milk them last.
- Cull cows that do not respond to treatment.
- Use excellent milking hygiene, including wearing gloves during milking.
- Minimize liner slips (squawking).
- Ensure properly functioning milking equipment.
- Complete post milking teat dip coverage.
- Screen purchased animals to prevent the entry of contagious pathogens.
- Screen bulk tank milk and cows with clinical mastitis or high SCC to identify contagious pathogens quickly.
Environmental organisms (Strep and Strep like organisms (SSLO), Coliforms, Staph species)
As the name implies, environmental organisms live in the cow’s environment so preventions should focus on cow housing and milking time routine. Cows can be infected throughout the day by contaminated bedding, mud, dirt and manure.
The risk of infection is directly related to the number of organisms on the teat end. Environmental organisms can also spread from cow to cow during the milking process.
Cow prep should focus on teat hygiene and drying before unit attachment. Because approximately half of all mastitis infections occur during the dry period, it is important to keep dry cows clean and dry. Control environmental organisms by:
- Providing cows with clean, dry lying areas.
- Providing clean, dry housing for dry cows and heifers.
- Focusing on clean dry teats during cow prep.
- Completing post milking teat dip coverage.
- Minimizing liner slips (squawking).
- Using internal or external teat sealants at dry off.
- Culling chronic cows.
- Vaccinating with E. coli bacteria (proven to reduce the severity of coliform infections).
Other organisms (Bacillus spp. Pseudomonas spp, Prototheca spp. yeast)
Most mastitis problems are caused by common mastitis pathogens; however, other less common organisms can sometimes be a problem. Treatment strategies vary in scope and success. Your herd veterinarian and the University of Minnesota Lab for Udder Health are the best resources to investigate and develop an action plan for eradication of these organisms.
Step 2: Develop a monitoring plan
Identify specific monitors to determine progress. The table below has benchmark monitors from Minnesota DHIA herds. Monitors to consider include:
- Bulk tank SCC.
- Incidence of clinical mastitis – defined as the percent of cows with clinical mastitis on a monthly or annual basis.
- A good goal of less than 5 cases/100 cows milking cows/month.
- An excellent goal would be less than 1–2 cases/100 cows milking/month.
- New infection rate defined as SCC less than 200,000 during the previous month and greater than 200,000 in the current month.
- Goal is less than 8 percent per month.
- New infection rate in fresh cows and fresh heifers.
- Percent of chronically infected cows, which is the percent of cows with 2 or more consecutive months with an SCC greater than 200,000.
- Bulk tank culture results.
- Cows culled for high SCC.
Somatic cell count benchmarks for Minnesota DHIA herds1
| Herd SCC category | Average SCC | Percent of herd > 200,000 | New infection rate % | Percent chronic |
|---|---|---|---|---|
| <200,000 | 157 | 16.4 | 8.1 | 8.3 |
| 200,000-299,000 | 251 | 24.7 | 10.5 | 14.2 |
| 300,000-399,000 | 350 | 32.9 | 12.5 | 20.4 |
| >400,000 | 513 | 43.4 | 14.2 | 29.2 |
1Reneau and Leuer, 2011
Step 3: Adjust plan as needed
Meet monthly with key dairy advisors and evaluate progress. If adequate progress is not being made, there are two possible reasons:
- The action plan is not correctly being implemented.
- The SCC problem was not properly identified, and incorrect action plans were developed.
If adequate progress is not being made, modify the plan and monitor the new results. As milk quality improves, continue to monitor key control points and make changes to meet the farm’s goals.
The Quality Counts site contains many excellent resources and tips on improving and maintaining low SCC milk.
Reviewed in 2023