Mastitis and the Environment

by Dr. Terri Taraska, Professional Services Veterinarian

 
Each year a farm will use various products to treat mastitis. Udder cleanliness is an important factor contributing to mastitis for both the dry and lactating cows. When the teats and udder are wet and dirty, bacteria have the opportunity to infect the udder. The amount of exposure to mud and manure in the cow’s environment affects the rate of subclinical and clinical mastitis.
 
A Udder Hygiene Scoring Chart (www.uwex.edu/milkquality) used by farmers to rate udder cleanliness in the herd on a scale from 1 to 4:
 
  • Score 1—Free of dirt
  • Score 2—Slightly dirty (2 to 10 % of surface area is dirty)
  • Score 3—Moderately covered with dirt (10 to 30 % of surface area is dirty)
  • Score 4—Covered with caked on dirt (> 30 % of surface area is dirty)
     
Udders scored 3 and 4 (dirty) have higher somatic cell counts and the rate of mastitis is higher. According to Dr. Ruegg, when this scale is used, <15% of cows should have an Udder Hygiene Score of 3 or 4.
 
The negative effect of the environment on the dry cow increases as the cow matures; i.e., the more likely she is to develop new intramammary infection. Factors affecting this increase of new infections over time include previous exposure and infection with mastitis pathogens and decreased patency of the teat sphincter. According to Dr. Ruegg, older cows not only have a greater risk of mastitis but also have poorer treatment success. Other general observations by include:
 
  • Cows with a history of clinical mastitis have a reduced chance of cure
  • Cows in early lactation have a greater chance of recurrence
  • Cows that had a clinical case of mastitis in the previous lactation are 4 times more likely to have clinical mastitis in the next lactation
 
If and When a Cow Needs To Be Treated
A set of treatment protocols established with the veterinarian should be in place for the caretaker. In Dr. Ruegg’s Ten Smart Things Dairy Farms Do To Achieve Milking Excellence (2001), she suggests 4 categories of treatment as a guideline:
 
I- Abnormal Milk--give oxytocin (band leg), use a Quarter Milker and take a milk culture if not normal; the goal is to have 70% of mastitis cases in this group
 
II- Abnormal Milk + Swollen Udder--give oxytocin (band leg), take a milk sample, freeze it and treat with an intramammary tube and put her in a sick pen; the goal would be to have 20 to 25 % of mastitis cases in this category. (If the percentage of cows in this group becomes > 25 %, early cases of mastitis are being missed.)
 
III- Abnormal Milk, Swollen Udder and Body Temp > 103, Off Feed--treat as category II plus give fluids and products to relieve inflammation. Call your vet.
 
IV-Cows with Mastitis, Down and Dehydrated--immediate attention from your vet
 
In conclusion, setting up mastitis protocols plus good management will lead towards less mastitis in your herd and quality milk for the consumer.