Antibiotic residues in milk samples obtained from cows after treatment for papillomatous digital dermatitis.

OBJECTIVE: To determine whether there would be detectable antibiotic residues in milk obtained from dairy cattle with papillomatous digital dermatitis (PDD) after topical treatment with oxytetracycline. DESIGN: Randomized controlled clinical trial. ANIMALS: 28 lactating Holstein cows with PDD. PROCEDURE: Cows were assigned to 2 treatment groups. Treatment 1 (n = 16) consisted of spraying of PDD lesions with 15 ml of a solution containing 100 mg of oxytetracycline/ml; lesions were sprayed twice daily for 7 days, using a garden sprayer. Treatment 2 (n = 12) consisted of a one-time application of a bandage that consisted of cotton soaked with 20 ml of a solution containing 100 mg of oxytetracycline/ml. Milk samples were obtained before and after treatment and assayed for tetracycline content by use of high-performance liquid chromatography and a commercially available tetracycline screening test. RESULTS: None of the cows in either treatment group had violative residues of oxytetracycline in milk samples. CONCLUSIONS AND CLINICAL RELEVANCE: Producers treating lactating cows that have PDD, via topical application of oxytetracycline solution at the concentrations reported in this study, have a low risk of causing violative antibiotic residues in milk.