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New - Make a Plan to Root out Costly Subclinical Mastitis

November 9, 2020

Subclinical mastitis is exactly what it sounds like – it’s the hidden mastitis on your farm. Most dairy producers are not detecting it simply because cows aren’t showing the clinical signs that most milkers look for during the milking procedure. If you don’t have a plan to continuously seek out your subclinical cows, it can be very costly to your farm. 

Impact of subclinical mastitis 

Subclinical mastitis is a huge financial burden on farms. A cow that has subclinical mastitis will give less milk during her lactation compared to the amount she potentially could have produced without the infection or inflammation from the udder. Reduced production throughout the lactation from subclinical cows can cause astronomical losses, according to Amber Yutzy, Penn State Dairy Extension educator.

“It’s the same for clinical cows too, but clinical cows are often found and treated very quickly. Subclinical cows are missed,” she said.  “There’s also the loss of cows due to culling because with chronic subclinically-infected cows, a cure may not be achieved with routine treatment. This results in increased treatment costs and labor, not to mention the loss of premium payments due to higher somatic cell counts (SCC).”  

Monitoring techniques

Farms can successfully monitor subclinical mastitis. It starts with individual cow-side testing, such as the CMT test or similar tests on the market, that will help detect subclinical mastitis. Some parlors have testing within their milking units and their on-farm computer programs that are looking for high SCC cows. Farms who utilize Dairy Herd Improvement Association’s (DHIA) monthly records can use that information to identify cows with SCC counts higher than 200,000.  

“When we're trying to combat SCC issues on farms, subclinical cows are the number one thing we're looking for on monthly DHIA testing records,” said Yutzy. “Any cow that's testing 200,000 SCC or higher, I have producers go out to the barn and use their decision-making tools. For example, use the CMT paddle to see if she's infected in one or more quarters because DHIA tests are a composite test. One quarter can be very high, and the other ones low, so she's staying hidden for a longer period of time within the herd with a moderate somatic cell count.”

Next, look at a cow’s DHIA records over time to determine: 

  • Is she chronic? 

  • Is this a new infection? 

  • Is she a candidate for treatment?

  • Is she a candidate for cull? 

  • Am I going to culture her and see what kind of bacteria she has? 

  • Have I treated her previously? 

  • Is she pregnant?

Using the answers gathered at the individual cow level will help decide how to handle her case based on what is best for the herd and that specific cow.

Value of culturing 

“If she is positive in a quarter and you plan to treat her in some way, culture the quarter and see what bacteria you're dealing with,” she explained. “There are many different families of bacteria that are mastitis-causing organisms. But if we know which family the bacteria fall in, you and your veterinarian can make a better treatment decision for her. If you’re blindly treating cows, the chance of a cure is lower, and your income loss may be higher.”

Many farms can culture on-farm and have results in 24 hours. Depending on which bacteria family the organism falls in, work with your veterinarian to have a standard operating procedure on treatment protocols.

“When I'm working with a producer, we make a plan that outlines how you're going to handle the cows that are over 200,000 SCC on your farm,” she said. “The milk price has been low for many years; and if farmers aren't making profitable decisions, it's hard to make it in the dairy industry. For profitability and growing the herd into the future, I think it's important to make a plan and use all the tools available to solve inefficiencies like subclinical mastitis.”


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