PubMedDate not supplied
10 cows (German Brown x Brown Swiss) with 29 infected quarters (14 Staphylococcus aureus, 10 esculin positive streptococci, 5 Staphylococcus spec.) were treated daily after morning milking over a period of 4 days. Ampicillin and cloxacillin (500 mg each per dose) were administered to all 40 quarters intracisternally. During the evening milkings on 4 test days (day 3 before treatment, day 1 of treatment, days 5 and 9 after the last treatment), electrical conductivity based on 25 degrees C (EC) was measured in fore milk. To avoid ejection of alveolar milk, EC measurement was the first contact to the udder. Independent of the initial level, EC of all quarters was elevated by 2.1 mS/cm on average at the first milking following the first treatment. 9 days after the end of treatment, EC had declined to the initial level in all quarters classified as mastitic, non specific and latent infected before treatment. By contrast, EC values of healthy quarters remained elevated compared to their initial level (p < 0.01). This might be due to increased cistern tissue permeability caused by mechanical and pharmacological effects of antibiotic treatment. Despite the fact that somatic cell count and total bacteria count were reduced by treatment (p < 0.01), results showed that EC measurement on the first days following treatment was unsuitable for checking the success of treatment.