Absorption, Distribution, and Excretion of Penicillin and Dihydrostreptomycin in Dairy Cows Following Intramammary Infusion

Six dairy cows were given intramammary infusions of penicillin and dihydrostreptomycin in a 3 replicate experiment with 3 treatments in 1, 2 and 4 quarters. Blood, milk and urine were collected after each test and muscle, fat, liver and kidney were assayed from each treatment after the third test. Both antibiotics were detected in the milk beyond the recommended withdrawal time and also in the milk from untreated quarters. Peaks in sera were reached within 2 to 4 hours post-treatment and were directly related to the number of quarters treated. Some penicillin persisted in urine for 14 days and some dihydrostreptomycin persisted for 15 days. Both antibiotics were detected in the liver and kidney. There was more penicillin in the kidney medulla and more dihydrostreptomycin in the kidney cortex.