Susceptibility of Broilers to Coccidiosis Following Early Coccidiostat Withdrawal

THE use of preventive medication for coccidiosis protection is now virtually universal in management of commercial broiler flocks. This is accomplished by mixing a coccidiostatic drug into the feed. Medication may be discontinued before marketing for several different reasons. Because of Food and Drug Administration regulations on certain drugs, it is sometimes necessary to withdraw the drug several days before the birds are marketed to allow tissue residues of the drug to diminish to permitted levels. This is particularly true if the drug is used in combination with an arsenical growth-promoting agent. Other drugs have no withdrawal requirements, however, they can be withdrawn for reasons of economy and convenience. In one broiler feeding program starter ration is fed for 28 days, grower ration from 29–53 days, then “withdrawal ration,” which does not contain the medication, is fed until birds are marketed. In other feeding programs the coccidiostatic drug may…