Short communication: Anesthetic residues in milk after topical application during treatment of hoof lesions in dairy cows

摘要

Hoof lesions in dairy cows are usually treated bytrimming the hoof. However, trimming by itself cancause severe pain or exacerbate already existing pain.Hoof trimming is usually not carried out by trainedveterinarians, and pain management is not provided.Pain control during trimming is not only an ethicalobligation but also allows for better manipulation andmore meticulous treatment. Tri-Solfen (Bayer AnimalHealth, Pymble, Australia) is a spray gel containinglidocaine, bupivacaine, and cetrimide that is easily appliedtopically and has demonstrated pain-mitigationeffects during and after hoof trimming. In the EuropeanUnion, these local anesthetics are not approved for usein food-producing animals because of a lack of residuedata and concerns about genotoxic effects in cattle andhumans. The aim of this study was to assess lidocaine,bupivacaine, and 2,6-xylidine residues in milk after Tri-Solfen application in dairy cows. Five dairy cattle in thedry-off period were enrolled in the study based on clinicalevidence of lameness (score ≥3 on a 5-point scale).After cleaning and superficial trimming, we applied 3to 14 mL of Tri-Solfen to the lesions before continuingtreatment. Two milk samples were collected per animalin the following 4 milkings and analyzed in a referencelaboratory. Residues of lidocaine above the limits ofquantification (0.2 μg/L) were found in milk samplesin the first milking 6 h after treatment in only 2 cows.This study shows that excretion of local anestheticsand their metabolites in milk after topical applicationof Tri-Solfen is negligible and even undetectable afterthe first milking 6 h post-treatment.