Milk antimicrobial residues in Holstein dairy cattle treated for toxic puerperal metritis
DOI:
https://doi.org/10.21423/bovine-vol36no2p141-146Keywords:
antibacterial agents, antibiotic residues, benzylpenicillin, beta-lactam antibiotics, ceftiofur, cows, dairy cows, drug residues, endometritis, food contamination, food safety, milk, oxytetracycline, tetracycline, antibioticsAbstract
The objective of this study was to determine the presence of antimicrobial agents in milk and the time milk from cows treated for toxic puerperal metritis remained positive for antimicrobial residues. 51 Holstein dairy cows were divided into 3 treatment groups: Group 1 was treated with penicillin; Group 2 was treated with penicillin and tetracycline; and Group 3 was treated with ceftiofur sodium. Cows in Groups 1 and 2 received a daily intramuscular injection of procaine penicillin G at the standard farm-wide dose of 18 million units for 5 consecutive days, nearly 4 times the recommended dose of 3000 U/lb (6600 U/kg). In addition, cows in Group 2 were infused with 6 g of oxytetracycline diluted in 75 ml of sterile water on days 1, 3, and 5. Cows in Group 3 received a daily intramuscular injection of ceftiofur sodium at a standard farm-wide dose of 1 g for 5 consecutive days. Milk samples were collected on day 1, before the first dose of antimicrobial agent was administered, and on days 6 through 12 after the final day of treatment with antimicrobial agents. LacTek B-L (beta-lactam), LacTek TC (tetracycline), and LacTek CEF (ceftiofur) test kits were used to determine penicillin, tetracycline, and ceftiofur sodium residues, respectively, in milk samples. All 3 test kits used in this study have been phased out of production and are no longer available. Milk from 9 of 17 cows treated with penicillin was positive for beta-lactam residues for an average of 3.44 days post-treatment. In a separate group, 6 of 17 cows treated with penicillin were positive for beta-lactam residues for an average of 3.66 days post-treatment. Nine of 17 cows treated with oxytetracycline were positive for tetracycline residues for an average of 1.22 days following treatment. No milk residues were detected in cows treated with ceftiofur sodium. Antimicrobial residues were found in milk from cows treated with penicillin and oxytetracycline for 1 to 7 and 0 to 3 days, respectively, from the last day of treatment. In this study, milk from cows treated with penicillin tested positive for residues longer than expected and longer than the labelled withholding time. Antimicrobial screening may be necessary to prevent food contamination.
