By Heather Schlesser

Many farmers know that mastitis is a disease of the mammary gland caused by bacterial infection, and that it is the most common and costly health disorder of dairy cows. Mastitis causes a loss of income on dairy farms due to discarded milk, lost production, reduced milk quality and treatment costs. Overall production loss for the average U.S. dairy farm is estimated at $110 per cow annually. Due to these facts, farmers know it is important to watch for high somatic cell counts as an indicator of a mastitis outbreak.

Bulk tank sampling tells you the farm’s total somatic cell count and can even give an indication if a problem exists, but it does not pinpoint the culprit animals. Identifying animals with mastitis has traditionally been done by observing clinical signs of mastitis, such as abnormal looking milk or a swollen udder or quarter at milking time. The California Mastitis Test can also be performed to identify quarters with high somatic cell counts.

Some dairy producers have employed the use of Dairy Herd Improvement companies to tell them somatic cell count, butterfat and protein percentages. DHI uses an electronic somatic cell count from each cow to estimate milk somatic cell counts. Although DHI testing gives a reliable and accurate estimation of somatic cell counts, it does not identify which quarter or quarters are affected with mastitis. DHI testing takes a composite sample of all four quarters, giving you one score for each animal.

Early detection of the presence of an infection can lead to timely management decisions, which can reduce the economic impact of mastitis. Conducting electronic somatic cell counts on-farm has not been practical in the past. However, a few companies have developed methods for assessing somatic cell counts on-farm. These cow-side methods allow a farmer to test individual quarters or a composite of all four quarters during milking.

The PortaSCC uses an algorithm to convert results of an enzymatic reaction into an estimated somatic cell count. The PortaSCC takes 45 minutes to get a result. There is also a PortaSCC quick test that takes only five minutes. Results are determined by matching the color change to an indicator strip. Care should be taken if using the PortaSCC, as determination of color is subject to the interpretation of the reader.

The Direct Cell Counter and C-Reader system use electronic counting of somatic cells. Somaticell is a modified Wisconsin Mastitis Test that is performed in a few minutes and provides results as an equivalent somatic cell count. Researchers have tested these hand-held devices against the gold standard, electronic somatic cell count, to determine their accuracy and reliability. Results of quantitative tests like the Direct Cell Counter, C-Reader and Somaticell have greater correlation with electronic somatic cell counts.

Due to the negative impact of mastitis on farm productivity, all farms should have a detection and treatment system in place. When producers are considering additional tools for their “mastitis prevention toolbox,” they should choose them according to test performance, ease of use and cost. Each farm situation is unique, and the tools used will need to fit that operation. 

Schlesser is the Marathon County Extension dairy agent. This column is provided by the University of Wisconsin Extension Dairy Team.