Korean Journal of Veterinary Research 1993;33(4):649-655.
 Effects of γ-Irradiation from Cobalt-60 on pathogenicity of Eimeria tenella Hee-jeong Youn1, Young-bai Kang1, Du-hwan Jang2 1Department of Parasitology, Veterinary Research Institute of RDA in Korea2Department of Parasitology, College of Veterinary Medicine, Seoul National University Cobalt-60 감마선 조사가 Eimeria tenella 의 병원성에 미치는 영향 윤희정1, 강영배1, 장두환2 1가축위생연구소2서울대학교 수의과대학 Abstract A series of experiments on the effects of ${gamma}-irradiation$ was performed to reveal the pathogenicity of ${gamma}-irradiated$ oocysts of E tenella from Cobalt-60 and its progeny. The SPF chickens were inoculated with differnt doses of radiation and inoculum. The level of 100 Gy ${gamma}-irradiation$ from $^{60}Co$ and the level of inoculum with $1{ imes}10^4$ oocysts were recognized more pathogenic than those of the other groups by comparison of body weight gains, blood in feces and lesion scores. The signs of blood in feces, lesion score and the number of excreted oocysts in the feces were revealed as the lowest in the group of the ${gamma}-irradiated$ oocysts, the average in the group of the 1st and the 3rd progeny, and the highest in the group of non-irradiated oocysts of E $tenellgrave{a}$. The body weight gain of the group immunized with ${gamma}-irradiated$ oocysts of E tenella was higher than those of the non-irradiated, the 1st and 3rd progeny groups. The body weight gain of the groups immunized with the 1st and the 3rd progeny of E tenella were higher than that of the non-irradiated group. The feed conversion ration of the group immunized with ${gamma}-irradiated$ oocysts of E tenella was lower than those of the non-irradiated, the 1st and the 3rd progeny groups. The feed conversion ratios of the group immunized with the 1st and 3rd progeny of ${gamma}-irradiated$ oocysts were lower than that of the group infected with non-irradiated E tenella. The anticoccidial index(ACI 190.6) in the chickens immunized with the ${gamma}-irradiated$ oocysts of E tenella and those(ACI 142.8 and 107.4) of the 1st and the 3rd progeny groups were higher than that (ACT 87.4) of the group infected with non-irradiated E tenella. It was thought that the pathogenicity of ${gamma}-irradiated$ E tenella would be recovered according to increase the number of generation passaged in chicken. Key Words: Eimeria tenella, Cobalt-60, ${gamma}-irradiation$, pathogenicity, the 1st and the 3rd progeny, Anticoccidial index