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20-10 Depletion of Dexamethasone in Cattle: Food Safety Study in Dairy and Beef Cattle
Research Lead: Dr. Ron Johnson , University of Guelph
Executive Summary
Dexamethasone is a glucocorticoid-type steroid that has been approved in Canada as an injectable and oral formulation for some time in dairy and beef cattle for treatment of various medical conditions. Currently no maximum allowable residue limit (MRL) at processing is approved by Health Canada for milk or edible tissues (muscle, kidney, liver, fat) in cattle. As such, Health Canada and the Canadian Food Inspection Agency (CFIA) require "zero levels" in all food products obtained from cattle treated with dexamethasone. Additionally, approved withdrawal times or dexamethasone depletion studies are not available to ensure drug residues in milk and edible tissues are at a safe level for human consumption. The proposed project will conduct a dexamethasone depletion study according to Health Canada recommended study guidelines (VICH guideline no. 48) [1] to assess dexamethasone depletion in lactating dairy cattle milk and in edible tissues from beef cattle. The proposed project will greatly assist veterinarians and their producer clients with rational withdrawal times for dexamethasone use in cattle that will ensure minimized risks of violative drug residues in cattle processed for human consumption, while enhancing public and international trading partner confidence with Canadian livestock practices. The proposed project fits very well with BFO's Research Priorities, particularly food safety, as well animal health and welfare are addressed. Further, the study results will allow the Canadian Global Food Animal Residue Avoidance Databank (CgFARAD™) to recommend revised withdrawal times when dexamethasone is used extra-label in lactating dairy cattle and beef cattle by veterinarians in Canada.