Antibiotic Treatment of Lactating Cows

Abstract

The food animal practitioner of today faces a number of dilemmas when deciding how to treat a sick lactating cow with an antibiotic. What is the most effective drug? What dose? Is the drug approved for use in lactating cows? If so, is it approved at the dose he or she wants to prescribe? Is it approved by the route of administration he or she wants to use? If the drug is used in an extralabel manner, what should be the recommended withdrawal time for milk? Can the withdrawal time be accurately confirmed by a cowside residue test?

Several drugs will not be discussed in detail in this paper. There has been a voluntary moratorium against the use of gentamicin and other aminoglycosides in cattle since October 1994. All sulfonamides except sulfadimethoxine have been prohibited in lactating dairy cows since July 1992. Dihydrostreptomycin is no longer available in combination with penicillin, and so essentially is not being used. Tilmicosin results in excessive periods of milk residues, up to 31 days in one study, and so should be avoided.¹