%L eprints115 %X Coccidiosis is a disease found in poultry caused by parasitic protozoa, namely Eimeria tenella (E. tenella), which may lead to high rates of morbidity and mortality. To prevent coccidiosis, vaccination is required to inactivate and attenuate E. tenella protozoa. One of the compounds applied for attenuation is formaldehyde. Formaldehyde reduces the pathogenicity of an organism by creating rigidity in its structure. As a result, the organism cannot inflict disease and has a higher impact on building antibodies although it is still alive. The current research was an experimental study aimed to determine the formalin potential in attenuation of E. tenella pathogenesis in terms of oocyst production. The present study was conducted using the completely randomized design method. A total number of 25 broiler chickens were applied and their feces were tested to observe oocysts production and clinical symptoms. The obtained data would be analyzed by the ANOVA statistical test. The treatment groups presented clinical symptoms of E. tenella infection. The number of oocysts in treatment group I fluctuated from the lowest number which was zero on day five and then increased by day six, seven, and eight and it has reached the peak with the most significant amount of 4,050,460 oocysts on day nine. The treatment group II with the same condition reached its peak with the highest number of 1,363,160 oocysts on day nine. The treatment group III peaked with the most significant number of 618,960 oocysts on day nine. In addition, the treatment IV group attained the apex with the highest number of 719,480 oocysts on day nine. Meanwhile, the treatment V group reached the highest number of 284,200 oocysts on day nine. The difference in formalin concentration affected the amount of E. tenella oocyst production of broiler chickens. Formalin soaking with a concentration of 1.2% was the most optimal concentration to attenuate E. tenella. %V 11 %T Formalin Potentials in the Pathogenic Attenuation of Eimeria tenella based on Oocyst Productions %I Scienceline Publication, Ltd %A R. D. Anggraini %A E. M. Luqman %A S. Budhy %D 2021 %J Journal of World's Poultry Research %K Broiler chicken, Eimeria tenella, Formalin, Oocyst. %R 10.36380/jwpr.2021.14 %P 110-115 %N 1