Fact Sheet: Clinical Mastitis
Milk samples should be aseptically collected and frozen from all cows with clinical mastitis prior to the initiation of therapy. Samples can be periodically cultured to identify the infecting bacteria and to determine antimicrobial sensitivities. The treatment guidelines in Table ? should be followed and adapted to typical culture results obtained from clinical mastitis cases in the dairy. Intra-mammary antibiotics should be used more aggressively in herds with predominantly environmental strep problems as compared to those herds with predominantly coliform infections.
Residue Avoidance and Quality Assurance
Milk and meat should be withheld from human consumption for appropriate times following drug usage. Withholding times should correspond to the manufacturer’s label when used according to the label, and when only one drug is used. The veterinarian must provide withholding recommendations when drugs are used in an extra-label manner, and when two or more approved drugs are used concurrently.
Records of drug usage should be kept to help to minimize the chance of adulterated milk or meat being sold for human consumption. Drugs should be stored and labeled according to procedures described by the PMO. A review of the 10 critical control points that aid in residue prevention, a listing of FDA approved drugs and screening tests for them, along with a sample record system is available in the Milk and Dairy Beef Residue Prevention Protocol*.
As with any intervention that is made on a dairy, it is nice to know if it works. Protocols used to assess treatment efficacy should be agreed upon at the initiation of a new treatment. For example, the number of cows with chronic infections can be determined at the onset of a nonantibiotic clinical mastitis approach, and monthly thereafter. A steady rise in the number of cows with chronic infections, without a significant change in the number of new infections, may indicate that the nonantibiotic treatment regime was not effective.
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Biosecurity and Expansion
Contagious mastitis organisms (Streptococcus agalactiae, Staphylococcus aureus, and Mycoplasma) can easily be brought into the herd with purchased cattle. Ideally, the bulk tank of a herd should be cultured (aerobic and mycoplasma) three times at weekly intervals prior to purchase. An absolute minimum of one bulk tank culture should be run prior to purchase. Incoming cattle should be isolated for three weeks prior to mixing with the home herd. All purchased cattle, including heifers, should be cultured (aerobic and mycoplasma) upon entry to the herd or at freshening.