coccidiostatic, in which growth of intracellular coccidia is arrested but development may continue after drug withdrawal, or coccidiocidal, in which coccidia are killed during their development.

 

The natural development of immunity to coccidiosis may proceed during the use of anticoccidials in the feed. However, in the production of broilers during a short grow-out of 37-44 days, this may be of little consequence. Natural immunity is important in replacement layer pullets because they are likely to be exposed to coccidial infections for extended periods after termination of anticoccidial drugs. Anticoccidial programs for layer and breeder flocks are intended to allow immunizing infection while guarding against acute outbreaks.