Gebreab, Feseha (Prof)Gari, Getachew2018-06-282023-11-082018-06-282023-11-082004-06http://etd.aau.edu.et/handle/123456789/4614The objective of this study was first to investigate the prevalence of poultry coccidiosis and to identify the coccidial species occurring in the study area on local strain and Rhode Island Red breed chicken. The duration of the study was from September up to December, 2003 and the sample size for local strain and RIR breed was 160 and 31 respectively. The study involved questionnaire survey, fecal examination, necropsy examination and identification of coccidial species based on their morphology, predilection site in the intestine and sporulation time. Frequency detection of oocyst in the fecal samples from RIR breed and local strain chicken was 80.65% and 61.25% respectively. This finding indicated that coccidial infection in RIR breed was significantly higher than in local strain chicken (p < 0.05). The lesion score and mean oocyst output per gram feces was also considerably higher in RIR breed than in local strain chicken (p < 0.05, P < 0.001 respectively), which may be the difference due to management system and breed. Clinical coccidiosis occurrence in RIR breed and local strain chicken was 22.58% and 12.25% respectively. There was no statistically significant difference in clinical coccidiosis occurrence between the two genotype chickens and system. Eimeria species identified in descending order of their occurrence were E. tenella, E. acervulina, E. necatrix, E. maxima and E. mitis. Mixed infections were the predominant in both production systems. E. mitis was tentatively diagnosed for the first time in Ethiopia. The second study was experimental study was conducted to compare the natural resistance of local strain and RIR breed chicken to acute infection with E. tenella field isolate. The resistance was assessed based on measuring and analysis of the parameters; oocyst production, body weight gain/loss, lesion score, packed cell volume and morbidity rate. A total of 218 chicks were assigned for the experiment out of which 141 local strains and 77 RIR breed were randomly allocated into the experimental test and control groups. Sex difference within each genotype was also taken in to account. The test groups were inoculated with 150,000 sporulated oocysts of E. tenella per bird suspended in 1ml distilled water and given per os directly in to the crop. Body weight and packed cell volume measurements were taken for all birds twice, on day 0 and 8 post infection. The birds were necropsied 8 days post infection for lesion score. The morbidity rate in RIR breed was lower (p < 0.001) than the local strain chickens and no mortality during the patent period. Moreover, body weight depression in RIR breed was significantly lower (P < 0.05) than the local strain chicken. However, lesion score and oocyst production was significantly higher than the local strain chickens (p < 0.001, p < XI 0.001). This indicated RIR breed demonstrated better resistance to overcome the effects of the disease. Differences in natural resistance between males and females were not significant. However, under experimental infection there were some variations to the effects of the disease that females showed significantly higher body weight depression and larger oocyst production than males in both genotype chickens. Key Words: Coccidia, E. tenella, natural resistance, prevalence, infection, Rhode Island Red breed, Local strain chicken and Tiyo WeredaenCoccidiaE tenellanatural resistanceprevalenceinfectionRhode Island RedbreedLocal strain chicken and Tiyo WeredaThesis