The influence of the dosage of antibiotics on the excretion via milk

While trying to increase the curing rates by treating dairy cows during lac tation with rapidly excreting compounds the dosage recommended by the manuf acturer and by literature is generally and commonly exceeded. Effects on th e setting of the withdrawal period which is, among other things, also dose- related, are not taken into account here. The subject of this study was to investigate the very problem and to test if drug overdosage does result in an extension of the elimination of the active substances which may conseque nce a longer withdrawal period. For two authorized intramammarica both the recommended dosage and an overdosage were applied in three dairy herds to e leven cows with healthy udders and normal lactation; the intramammarica wer e applied to two quarters of each udder three times at 24 hours intervals i n two stages of treatment, followed by each other at a given interval of ti me. The final comparison of the overdosage with the standard dosage resulte d for both test preparations, when applied intramammarily, in a 12 to 24-ho ur delay of drug excretion. A significant increase of the drug concentratio n in milk after an overdosage could be found in only one of the tested prep arations. Despite the extension of the elimination of both active substance s clearance occured within the respective individual withdrawal period; als o, the residual level recorded at the end of excretion was, in quantitative respect, below the maximum permissible residue level (mrl) fixed for the a ctive substances.