Effect of Milk Fraction on Concentrations of Cephapirin and Desacetylcephapirin in Bovine Milk after Intramammary Infusion of Cephapirin Sodium

Abstract

Treatment of clinical mastitis accounts for a substantial proportion of antimicrobial use on dairy farms. Intramammary (IMM) antibiotics are a mainstay of treatment for clinical mastitis, especially episodes caused by streptococci or staphylococci. For therapy to be successful, the antimicrobial treatment must attain and maintain an effective concentration at the site of infection. Accurate pharmacokinetic data are essential for determining appropriate treatment regimens and withholding times, especially when antimicrobials are used off-label, because milk is withheld from sale until antimicrobial residues drop below the tolerance concentration. Some studies use foremilk or total milk collected during milking for antimicrobial quantification, whereas many studies do not report sample type. Because antimicrobials distribute unevenly in the mammary gland, and because milk fractions differ in protein and fat concentrations which influence distribution, we hypothesized that antimicrobial concentrations differ in milk fractions after IMM infusion. Therefore, our objective was to compare antimicrobial concentrations in three fractions of milk 8 or 12 hours after administering an IMM antimicrobial to lactating dairy cows.