Mammary leukocyte response to drug therapy.

The possibility exists that antibiotics and anti-inflammatory agents will be used indiscriminately in attempts to reduce leukocyte or somatic cell counts in mammary secretions to conform with Interstate Milk Shippers quality standards for raw milk to be implemented July 1, 1986. Recent in vivo studies evaluating the effect of intramammary drug injection on milk leukocytes confirmed previous in vitro investigations demonstrating that certain drugs have a significant effect on leukocyte antimicrobial activity. Antibiotics commonly included in commercial infusion products used in this country such as penicillin G, semisynthetic penicillins, the mycins, cephalosporins, and sulfonamides did not affect leukocyte function. However, some drugs were detrimental, notably chloramphenicol, tiamulin, tetracycline, gentamicin, rifampicin, amikacin, and nitrofurantoin. In vitro investigations on the use of anti-inflammatory agents demonstrated that methylprednisolone had a stabilizing effect on leukocytes by maintaining viability and reducing degranulation, whereas flumethasone was detrimental to cell viability. The nonsteroid agent, ibuprofen, decreased viability and increased degranulation but also increased phagocytosis and bacterial killing. Intramammary infusion of anti-inflammatory agents was generally ineffective in lowering somatic cell counts of endotoxin-infused quarters, but certain drugs may be advantageous in limiting milk production losses during udder inflammation.