EN
The studies were carried out on 35 000 broiler chickens kept in two broiler-houses of Bios type and 11 000 replacement chicks (in two hen houses, 5 500 in each one). Two coccidiostatics were administered, i. e. Cygro (5 ppm) and Diclazuril (1 ppm) as feed additives in broiler chickens. Replacement chickens were being given the coccidiostatics for 16 weeks of their life. In one poultryhouse Diclazuril and in another one Lerbek were used. The efficacy of the coccidiostatics was assessed on the basis of the following factors: an average body weight (broilers — 4 and 8 weeks, replacement chickens — 8 and 16 weeks), feed consumption, mortality, anatomo-pathological examination after Johnson and Reid and parasitological examination. No differences between the broiler chickens treated with Diclazuril and chickens treated with Cygro were found. In the replacement chickens better findings were observed in the group treated with Diclazuril (lower feed consumption, mortality and oocysts output) in comparison to the Lerbek group of chicks. The results of the studies showed that Diclazuril had not side effects, prevented poultry from coccidiosis and did not suppress the development of natural immunity of poultry against the disease.