Excretion of penicillin G and dihydrostreptomycin from quarters of cows with experimentally induced staphylococcal mastitis
Mercer, H.D.; Geleta, J.N.; Porteous, L.A.; Condon, R.J.
American Journal of Veterinary Research 35(9): 1191-1196
1974
ISSN/ISBN: 0002-9645 PMID: 4138447 Document Number: 76511
In 10 cows inoculated with S. aureus to induce clinical mastitis, milk-out studies were conducted before and after inoculation to determine how mammary tissue involvement (acute mastitis) affected excretion rates of penicillin and dihydrostreptomycin given by intramammary injection. Penicillin concentrations were greater at the first milking after the last injection of antibiotic in infected quarters. Duration of excretion was significantly increased in infected quarters. Dihydrostreptomycin concentrations were also greater at the first milking after the last injection, but the duration of excretion did not differ between the infected and normal quarters. These results indicate that milk-out studies in mastitic quarters or an adjustment factor in normal quarters should be used to determine milk withdrawal intervals for antibiotics injected into the udder.