Efficacy of two antibiotic treatments in curing clinical and subclinical mastitis in lactating dairy cows

Aim. To compare the bacteriological and clinical cure rates for clinical and subclinical mastitis in New Zealand dairy cows following treatment with either an intramammary penicillin-dihydrosptreptomycin preparation or a subcutaneous injection of penethamate hydriodide. Methods. Milk samples were collected from clinical and subclinical cases of mastitis before and 14 and 21 days after initiation of treatment for bacteriological culture, somatic cell count determination and conductivity testing. Results. No significant differences in the bacteriological cure rate of major Gram-positive pathogens, clinical cure rate, somatic cell count or conductivity were found between treatments. However, the bacteriological cure rate of coagulase-negative staphylococcus infections and the overall bacteriological cure rate was lower for quarters treated with penethamate than with penicillin-dihydrosptreptomycin. Conclusions. The bacteriological cure rate of mastitis caused by major Gram-positive pathogens, the clinical cure rate, somatic cell count and conductivity did not differ between the two antibiotic treatments.