Utilizing feed to administer medication is not the preferred method as a calf that is not well will be less interested in eating. Animal health products are expensive. It makes no sense for the farmer to use more than is required to deal with specific health problems. All animal medications in Canada are approved by Agriculture and Agri-Food Canada and The Bureau of Veterinary Drus division of Health Canada. This system is the same as that for human health products.
Most provinces also require some form of product registration.
This is called residue data. An example of this would be 12 hour cold medication. In 12 hours the medication is gone from our body, and if our cold remains we must take more. The code was developed by a committee representing veal farmers, veterinarians, animal scientists, government and animal welfare agencies. Every animal must be inspected before and after processing in licensed meat packing plants.