Efficacy of parenterally or intramammarily administered tilmicosin or ceftiofur against Staphylococcus aureus mastitis during lactation

Two antibiotic preparations, tilmicosin and ceftiofur, were tested intramam marily and parenterally against Staphylococcus aureus mastitis in lactating cows. Neither product was effective as a lactating cow treatment at the do ses and durations of treatment tested. Injection or infusion of tilmicosin and infusion of ceftiofur resulted in reductions of bacteria present in mil k; however, only one quarter treated with infusion of tilmicosin was cured, and no cures were observed for the other treatments. Somatic cell counts w ere transiently reduced by infusion of ceftiofur and by infusion and inject ion of tilmicosin; however, they returned to pretreatment values by 28 d po sttreatment.