Mature oocysts of Eimeria tenella have been attenuated by Gemma irradiation 200 and 300 gray. Excystation of occysts were examined. The immunoeffeciency of irradiated oocysts were studied in broiler that vaccinated with 5x10° attenuated oocyst per chick. A total of 1500 day-old Faobro chicks were divided into 6 groups and were treated as follows: Group C: un vaccinated control. Group WF: Given the vaccine in the feed. 

Group DW: Given the vaccine in drinking water. Group CI: Given the vaccine in the crop. Group SP: Given the as a coarse spray. Group CIT: Given the attenuated vaccine in the crop (300 Gray) at day old and (200 Gray) at 14 days of age. 

The groups were challenged at 40 days of age with 5x104 viable oocysts of Eimeria tenella per chick. The clinical sings were recorded, the body weight was taken weekly, lesion score, packed cell volume, litter moisture, oocyst count in the litter and oocyst count in the caecal content were determined one week after vaccination, one day before challenge and one week after challenge. The protection ratio and mortality rate were estimated. Results revealed that attenuated oocysts have lost its pathogenicity, no clear clinical sings after vaccination has been recorded, but some chicks of all vaccinated groups show a slight bloody excretion. Some groups given significant increase in body weight in 

comparison with the control before and after challenge. The protection ratio was 93.5% for WF, 88.8% for DW, 98.3% for CI, 93.1% for SP and 82.2% for 

The mortality rate was significantly higher in the control than the CIT group. vaccinated groups, the CIT group recorded mortality that was 2.9% the CI and SP recorded 0% and the C group recorded 10% 

It was concluded that vaccination with all the methods used in this experiment provided good protection against challenge. The spray method was recommended best, then the drinking water and then with feed method.