Employees at Lundgren Dairy farms in Prairie Du Sac, Wis., thought it was impossible to achieve the milk-quality bonus offered at the dairy. Despite their efforts, the bulk-tank somatic cell count stood stubbornly at 260,000 — just 60,000 above the first-bonus level.

Fast forward one year. The bulk tank somatic cell count now consistently registers under 150,000, and employees receive the second-bonus level of $100 per month. The difference, explains owner David Lundgren, is that the dairy took a team approach to subclinical mastitis.

To achieve a bulk-tank somatic cell count of less than 200,000, he brought in milk-quality expert Andy Johnson. “Andy gave us the tools and showed us that we needed a team effort to go after subclinical mastitis,” explains Lundgren. The BTSCC has been below 200,000 since September 2006, and over the winter it stayed around 100,000. While earning an additional premium on milk sold to Grande Cheese was Lundgren’s initial goal, he has learned that when you reduce the amount of subclinical mastitis in your herd, milk production goes up and the number of clinical cases goes down.

Here are three reasons why you should focus on subclinical mastitis in your herd.

Remove chronic disease

When it comes to mastitis, most producers focus on the clinical cases and tend to overlook the subclinical varieties. After all, “you can’t fight an enemy that you can’t see” — and you can’t see subclinical mastitis. To many dairy producers, subclinical mastitis is not an issue because the milk is not abnormal and the cows don’t appear sick, explains Dave Rhoda, veterinarian with the University of Wisconsin’s Milk Money program. And, compared to other problems they may be dealing with, subclinical mastitis doesn’t even appear on the radar screen in many cases. 

What many producers fail to understand is that subclinical mastitis is a chronic form of disease. Some of the bacteria on farm today have become host-adapted, explains Jill Makovec, manager of education and information for AgSource in Verona, Wis. The bacteria cause an infection that goes undetected because it does not change the appearance of the milk. This allows the bacteria to make a home in the host — the cow’s udder. The cow’s immune system detects the infection and mounts an attack. That’s why the somatic cell count climbs above 200,000. (Research has shown that cows with an individual SCC above 200,000 have at least one infected quarter.) But, without visual signs, most producers don’t know the infection exists. This allows the bacteria to establish a long-term presence and become a chronic source of infection.

Subclinical infection has been shown to reduce milk production. And field observations have detected a correlation between subclinical mastitis and decreased fertility, adds Rhoda. Both are reasons that should encourage producers to remove chronic disease.

Market access

“We supply dairy food products in what has become a very consumer-driven industry,” says milk-quality veterinarian Andy Johnson, of Clintonville, Wis. If a consumer ever questions the quality of a dairy product, you risk losing that customer. And gaining that customer back can be difficult — if they ever do come back.

That’s why it is so important for every producer to put his best foot forward each and every day. Producing high-quality, low-SCC milk is one way to do that. Landmark research reported in the February 2000 Journal of Dairy Science showed that milk with a lower SCC has a longer shelf life. That’s because the enzymes generated by high numbers of somatic cells break down the protein and fat in milk, which leads to a sour taste, rancidity and bitterness. Research also has shown that milk with lower SCC boosts cheese yields. Combine these two factors with the increased use of ultra-high-temperature pasteurization and ultrafiltration today, and it’s easy to understand why some milk plants have opted to pay more for milk with lower somatic cell counts. And why other milk plants have made low-SCC milk a requirement for market access.

Johnson, who works with dairy producers across the country, says he knows of several milk plants that have sent letters to producers telling them to get their bulk tank SCC below 350,000 or to take their milk elsewhere. “If producers are waiting for someone to pay them to improve milk quality, they may very well find themselves without a market to sell their milk,” he says. 

It pays

Perhaps the biggest reason to address subclinical mastitis in your herd is that it pays. Even if your milk plant doesn’t pay quality premiums, lowering your somatic cell count leads to healthier cows, less clinical mastitis and higher  milk production.

Let’s go back to the 440-cow Lundgren Dairy in Wisconsin. In the spring of 2006, the dairy had a bulk-tank somatic cell count of 260,000. Today, the count stands at 139,000. But it wasn’t just the cell count that changed. Both the rate of new mastitis cases each month and the percent of cows freshening with an elevated cell count dropped. And milk production increased, as detailed here: 


Lundgren Dairy Farm

Spring 2006


Spring 2007


Bulk tank SCC 






Pounds of milk/cow/day






% cows SCC






% cows new infection






% infection in fresh cows







Research shows that each time you cut your somatic cell count in half — for example, from 800,000 to 400,000 — you gain 2 pounds of milk per day from heifers and 4 pounds of milk per day from cows, says Johnson. 

That’s a lot of extra milk. With each halving of the somatic cell count (also known as a linear score change of 1), a 1,000-cow dairy could recoup 3,000 pounds of milk or more per day worth $450 (if milk prices are $15 per hundredweight). 

Perhaps one of the most comprehensive studies to look at the economic return was reported in the July 2005 issue of the Journal of Dairy Science. Pam Ruegg, veterinarian and director of the Milk Money program at the University of Wisconsin, and her colleagues analyzed data from 113 herds that had completed the Milk Money program from 1999 through 2005. They subdivided data for low-SCC herds (less than 250,000), medium-SCC herds (250,001 to 400,000) and high-SCC herds (more than 400,000). During a four-month enrollment in the Milk Money program, bulk-tank somatic cell count dropped by an average of 34,000 in the low-cell-count herds; 53,000 in the medium herds, and 181,000 in the high herds. 

The value of increased milk production and decreased clinical mastitis was generally equal to or greater than the increase in milk-quality premiums received, explains Ruegg. The average value gained for the 113 herds from having less clinical-mastitis treatment cost was $2.24 per cow per month, and $1.12 per cow per month for increased milk production. Added together, the gains were greater than the average milk-quality premium of $3.24 per cow per month gained from a lower somatic cell count.

So, even if your milk plant doesn’t pay a quality premium, you can still reap financial benefits from improving milk quality on your farm. (The chart above summarizes the low-, medium- and high-cell count herds in the Milk Money study.)

“When you lower your cell count, the result is healthier cows, higher-quality milk and more profit for your dairy,” stresses Johnson. And although Lundgren was skeptical that his dairy could get below that 200,000 threshold, the last year has taught him that the premium earned for improving milk quality is just the tip of the iceberg. Increased milk production and decreased subclinical/clinical mastitis in the herd certainly add to his economic bottom line.

For more information

To learn more about the university of Wisconsin’s milk money program, and improving milk quality in general, check out this Web site: www.uwex.edu/milkquality.

The value of lower somatic cell counts

These results are from 113 dairies that completed a milk-quality-improvement program in Wisconsin known as Milk Money.



Low herds


Medium herds


High herds





250,001 – 400,000 SCC


>400,000 SCC


Decrease in SCC








Gain in premium








Value of extra milk








Decrease in cost of clinical mastitis treatment








Total gain








Source: Rodrigues and Ruegg, July 2005 Journal of Dairy Science.