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Virginia Cooperative Extension - Knowledge for the CommonWealth

Mastitis Tip of the Month-- Now You found Some Staph aureus Cows, So What???

Dairy Pipeline: November 2001

Gerald M. (Jerry) Jones
Professor and Extension Dairy Scientist,
Milk Quality & Milking Management

Successful control is gained only through prevention of new infections and cow culling. Staph aureus bacteria colonize abnormal teat ends or teat lesions. It can be spread from cow to cow via milkers' hands, wash cloths, teat cup liners, and flies. Infected cows must be segregated from the milking herd and milked last, milked with separate milking units, teat cup liners backflushed, or culled. Staph aureus mastitis is extremely difficult to control by treatment alone. Once an infection is established, it usually does not respond to antibiotic treatment. One exception might be to catch them when the infection is new, such as the first month their SCC increases. If they don't respond, don't keep treating them, because it likely will do no good. Also you're throwing away milk and taking a risk on an antibiotic residue violation. Once a staph cow, always a staph cow! Some staph infected cows may be negative on culture. If they have clinical mastitis, high SCC, or positive CMT, culture them again, but consider them infected until proven clean. In the past, I have recommended installation of automatic backflushing. Look for one additional reason to cull infected cows (low production, repro problems, or poor attitude, you name it). Often, it is not economically feasible to cull a staph cow that produces 80-90 lb milk. However, any cow that has had clinical mastitis in the same quarter for three or more occasions, or any cow whose milk has been withheld from shipment for more than 28 days during the current lactation, should be added to the cull list. It's important to keep mastitis records including cows and quarters treated and treatment used.

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