In-feed treatments are easier to administer and pose less environmental risk than bath treatments. Feed is usually coated with the drug and drug distribution to the parasite is dependent on the pharmacokinetics of the drug getting in sufficient quantity to the parasite. The drugs have high selective toxicity for the parasite, are quite lipid-soluble so that there is sufficient drug to act for approximately 2 months, and any unmetabolized drug is excreted so slowly that there are little to no environmental concerns.