Antibiotic residues in milk samples obtained from cows after treatment forpapillomatous digital dermatitis

Objective-To determine whether there would be detectable antibiotic residue s 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) co nsisted 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, usin g a garden sprayer. Treatment 2 (n = 12) consisted of a one-time applicatio n of a bandage that consisted of cotton soaked with 20 ml of a solution con taining 100 mg of oxytetracycline/ml. Milk samples were obtained before and after treatment and assayed for tetracycline content by use of high-perfor mance liquid chromatography and a commercially available tetracycline scree ning test. Results-None of the cows in either treatment group had violative residues o f oxytetracycline in milk samples. Conclusions and Clinical Relevance-Producers treating lactating cows that h ave PDD, via topical application of oxytetracycline solution at the concent rations reported in this study, have a low risk of causing violative antibi otic residues in milk.