Detecting mastitis through somatic cell counts on composite milk samples has created a lot of interest among DHI dairymen. How to interpret these reports has also ca used some confusion

South Dakota State University, Cooperative Extension

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South Dakota State University Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange SDSU Extension Fact Sheets SDSU Extension 1981 Interpreting Individual Cow Somatic Cell Counts Cooperative Extension South Dakota State University Follow this and additional works at: https://openprairie.sdstate.edu/extension_fact Recommended Citation South Dakota State University, Cooperative Extension, "Interpreting Individual Cow Somatic Cell Counts" (1981). SDSU Extension Fact Sheets. 806. https://openprairie.sdstate.edu/extension_fact/806 This Fact Sheet is brought to you for free and open access by the SDSU Extension at Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange. It has been accepted for inclusion in SDSU Extension Fact Sheets by an authorized administrator of Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange. For more information, please contact michael.biondo@sdstate.edu. Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. SDSU Extension ® For current policies and practices, contact SDSU Extension \,\Tebsite: extension.sdstate.edu Phone: 605-688-4792 Email: sdsu.extension@sdstate.edu SDSU Extension is an equal opportunity provider and employer in accordance with the nondiscrimination policies of South Dakota State University, the South Dakota Board of Regents and the United States Department of Agriculture. interpreting individual cow somatic · cell counts Cooperative Extension Service South Dakota State University U.S. De artment of Agriculture FS 753 interpreting individual cow somatic cell counts Myers Owens, Extension dairyman, and C.A. Kirkbride, DVM Detecting mastitis through somatic cell counts on composite milk samples has created a lot of interest among DHI dairymen. How to interpret these reports has also caused some confusion. Points to remember 1. Excluding counts taken the first week or last 2 weeks of lactation, most cows with cell counts between 500,000 and 1,000,000 are infected. The chances are 80% or greater that cows with cell counts above 800,000 have one or more infected quarters. This level indicates udder irritation with some loss of production. 2. Age of the animal plays a very important role in interpreting cell counts on composite milk samples. Second lactation and older cows with cell counts below 500,000 can generally be considered uninfected, although some infected cows may occasionally dip below this level. First calf heifers normally freshen without mastitis and with low cell counts (100,000 to 350,000). The cell counts gradually increase as the cow becomes older and has been exposed to injury and infection. Therefore, higher cell counts-up to about 750,000-can be considered normal in older cows. 3. Testing composite samples may hide an infected quarter. Because of the dilution effect, an infected quarter shedding 1,000,000 cells may not be detected when the three healthy quarters have cell counts of 350,000 or less. In this case the composite sample would have 550,000 or fewer cells and the mastitis in the one quarter would probably go undetected. 4. The DHI composite cell count does not indicate which quarter or quarters are infected. The affected quarters can only be identified by use of the California Mastitis Test (GMT) or an equivalent test of individual quarter milk samples. 5. Treatment of infected cows, if effective, may cause cell counts to decrease within 10 to 14 days. However, depending on the organisms, several weeks may pass before the cell count approaches a normal level. Cell counts may remain above normal throughout a lactation in a quarter that had a coliform or Strep ag infection in early lactation. If the treatment was successful, when the cow freshens again the count will be near normal. It is also possible that the treatment will reduce the number of organisms and cells temporarily, but not eliminate the infection. One way to determine if the treatment was successful is to wait at least 10 days after treatment, then have a milk sample from the quarter cultured. 6. Cows ( especially first and second calf heifers) with low cell counts may suddenly flare up with severe mastitis without prior warning. This occurs most frequently in the first 2 weeks after freshening. These cases are usually caused by coliform (digestive tract or environmental) organisms. Cows with low cell counts seem to be particularly susceptible to these infections, which usually result from unsanitary environmental conditions such as wet bedding, mud, and manure. 7. Information is incomplete on factors other than infection, age, and stage of lactation that influence cell counts. Infection is the single most important causeof high cell counts. Otherstresses such as a stepped-on-teat, udder injury, or systemicinfections may cause high cellcounts without udder infection. 8. Culturing milk for bacteria is the only way to determinewhether a high cell count is due to infection or some other stress. Culturing milk from high-count cows will help guide bothtreatment and controlprocedures. Wait at least 10 days after the last treatmentbefore taking milk samples forculturing.9. A veterinarian should beconsulted to evaluate cell countsand treatment of infected cows.Dairymen must learn to acceptthat there are some forms ofmastitis that do not respond totreatment even with modern"miracle" drugs and thatprevention and culling are theonly ways of eliminating suchmastitis.10. Individual somatic cell counts are also useful in selecting cows for dry treatment. Cows whose cell counts slowlyincrease through lactation (seecow 121, Table 1) probably have a low grade, subclinical infection. Dry cow treatment is often effective in eliminating this type of infection. Cows that have been treated during lactation and whose cell counts remain high are also candidates for dry-cow treatment or culling, depending on the severity and chronicity of the infection. 11. Cell counts also can be useful to dairymen when purchasing lactating cows. '---...--, ~ Table 1. Monthly cell counts In a dairy herd, by thousands (000's). Barn Lact. Fresh Days In Month High this name no. date mllk 8-4 9-8 10·2 11·5 lactation326 1 7-1 130 250 275 280 265 280 127 1 6-19 140 412 1240* 1585* 2122* 2112 243 1 5-8 173 846* 376 237 212 846 83 6 3-11 236 808* 795* 812* 815* 815 92 7 6-29 134 2569* 2810* 2543* 2790* 2810 121 3 4-19 245 480 526 656* 720* 720 36 2 8-17 125 686* 311 280 305 686 201 1 5-20 190 1659* 4683* 579 349 4683 *cell count over 600,000 Cows with composite milk cell counts in excess of 800,000-1 ,000,000 cells should not be purchased. In addition, all purchased cows should be quarter-cultured before they are added to the milking string. Cows shown to have Streptococcus agalactiae or Staphylococcus aureus infections should not be placed in the milking string until the infection has been eliminated. Sample counts and interpretation of them Table 1 shows somatic cell counts you might expect in a dairy herd. Cow 326: Young cow, recently fresh. Normal cell count should be 300,000 or less.Cow 127: Young cow, obviously has picked up infection between August and September tests., Identify problem quarter or quarters and culture. Treatment may be based on culture result. Cow cannot wait until dry period for treatment. Cow 243: Young cow with infection in early lactation and treated in August. Decrease in cell count indicates successful treatment. Cow 83: Older cow, cell count is intermediate. If GMT indicates all four quarters are about equal, no treatment is necessary. If one or more quarters are considerably higher than others, cultures should be taken. In any case, dry cow treatment is necessary. Cow 92: Older cow with chronic mastitis. Cull as soon as possible. Cow 121: Slowly advancing cell count, late lactation. Dry cow treatment recommended. Cow 36: Fresh 7 days when first somatic cell count run. Cellcount may be slightly higher atstart of lactation. Wait for next month's count. Cow 201: August countindicates infection. Treatment occurred in August. September cell count taken 10 days after treatment. Cell count will normally increase after antibiotic therapy and remain elevated for days or weeks depending on bacteria involved. Therefore, disregard September count and wait for October, which in this case indicates successful treatment. For earlier information on results of treatment, quarter milk samples could be cultured 10-14 days after treatment. Somatic cell counts on an individual cow basis can be a very useful tool in a mastitis control program. However, they must be interpreted correctly.Perhaps it is even more important to determine what factors are causing high counts and eliminate them. Treatment without correcting the cause is a waste of time and money. Acts of May 8 and June 30, 1914, in cooperation with the USDA, Hollis D. Hall, Director of Cooperative Extension Service, Issued in furtherance of Cooperative Extension work, SDSU. BrookinQs. Educational proorams and materials offered without regard to age, race, color, religion, sex, handicap or national origin. An Equal Opportunity Employer. File : 4.6-1 0-3M-79-3,000 rev ised at est imated 7 cents each-6-81mb-8174A. Photo courtesy of Jim Baird, Hoard 's Dairyman. c:cno • 0 C, en -■0 ~co ::::, -·::::, 0 ---o::::r CD (D 0 ..... CD C.O Q> !l) !l) =- - 3 -■ (D '"";,:;"< C, - < ... - 0 CD s»3- .... -·-cCD !l> ITT ::::, CJ)~ 0 C. ... --CD -■ o a::, C C, C CD - CD Cl))> -- :, ....s»co C: 0 '""::::,::::,o· <. en .... - ::::,-· C CD CD_,'"" C, - Cl) < en ca C -· -'""-(")· 0CD'< CD ~ 

Interpreting Individual Cow Somatic Cell Counts

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Interpreting Individual Cow Somatic Cell Counts

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