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Evaluation of Risks of Violative Milk Residues Following Extra Label Topical Administration of Tetracycline for Digital Dermatitis in Dairy Cattle


Tetracycline is a commonly used treatment of DD in dairy cattle; however, limited data are available regarding the risks of milk residues. Currently the maximum residue level (MRL) allowable for tetracycline in cow's milk in Canada is 100 parts per billion. The proposed study will evaluate the withdrawal time of milk tetracycline levels to the accepted MRL. Tetracycline will be applied topically in either a paste or in powdered form (under bandage wrap) at doses ranging from 2 grams to 25 grams to dairy cattle with severe DD. The project will also compare agreement of results among laboratory and commercial diagnostic test methods.

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Expected Benefits <br/>

Results of the proposed project will enable veterinarians in the Ontario dairy industry to write appropriate prescriptions with knowledge of dose and withdrawal times that can avoid milk tetracycline residues that exceed allowable limits. The results of the study will benefit the dairy industry and supports the Canadian Quality Milk program. The outcomes will help ensure the safety of milk, while also enhancing consumer and trading partner confidence and supporting animal welfare.

Johnson, Ron
University of Guelph
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