Evaluation of risks of violative milk residues following extra-label topical administration of tetracycline for digital dermatitis in dairy cattle

Abstract

Digital dermatitis (DD) is a commonly found foot lesion in cattle at the time of hoof trimming. At this point in time there are no licensed antimicrobials available for DD in North America, and DD is commonly treated with topical tetracycline antimicrobials at varying doses. This usage of topical tetracycline is extra-label drug use, and limited data is available to evaluate the risk of violative milk residues following treatment. Previous work that has evaluated the risk of violative milk residues only looked at one dosing regimen and used a tetracycline formulation that is currently not widely used by professional hoof trimmers or veterinarians. The objective of this project was to determine if various application methods or tetracycline dosages would result in tetracycline residue levels in milk.