fa پژوهشي Orginal research papers This study was conducted using butyric acid as a growth enhancer in the diets of <em>Clarias gariepinus</em> and <em>Oreochromis niloticus</em>. <em>C. gariepinus</em> (42.39 g&plusmn;1.17) were fed diets containing varying inclusion levels of butyric acid (BA); 0 (CG1), 0.5 (CG2), 1.0 (CG3), 1.5 (CG4), 2.0 (CG5) g kg ^-1, where, CG1 is the control or reference diet. <em>O. niloticus</em> (25.50 g&plusmn;0.50) were also fed diets containing varying inclusion levels of butyric acid; 0 (ON1), 0.5 (ON2), 1.0 (ON3), 1.5 (ON4), 2.0 (ON5) g kg ^-1, where, ON1 is the control or reference diet. Diets for <em>C.</em> <em>gariepinus</em> contained 40 % while those of <em>O. niloticus</em> had 35 % crude protein. Fish were fed to satiation twice daily in two equal portions for 12 weeks. At the end of the experiment <em>C. gariepinus</em> fed on diet CG5 (2 g kg^-1 BA) had an improved growth of over 600 % while <em>O. niloticus</em> fed diet ON4 (1.5 g kg^-1 BA) showed over 400 % improvement in growth when compared with those fed the control or reference diets. The highest carcass protein were also obtained in those fed BA diets when compared with their respective control diets. The results of the present study showed that there was better nutrient utilization in <em>C. gariepinus</em> and <em>O. niloticus</em> fed BA supplemented diets. Furthermore, there were no significant variations in the survival of fish fed BA diets when compared with their controls except for those fed ON4 which showed 100 % survival. Quality of water parameters were within the acceptable limits for the culture of fin fishes. Butyric acid, Growth enhancer, Clarias gariepinus, Oreochromis niloticus, Survival 403 412 http://jifro.ir/browse.php?a_code=A-10-1722-1&slc_lang=fa&sid=1 O.O. Omosowone 100319475328460029506 100319475328460029506 No Department of Fisheries and Aquaculture Technology, Federal University of Technology, Akure, Ondo State, Nigeria. Department of Fisheries and Aquaculture Technology, Federal University of Technology, Akure, Ondo State, Nigeria. A.A. Dada aadada@futa.edu.ng 100319475328460029507 100319475328460029507 Yes Department of Fisheries and Aquaculture Technology, Federal University of Technology, Akure, Ondo State, Nigeria. Department of Fisheries and Aquaculture Technology, Federal University of Technology, Akure, Ondo State, Nigeria. E.O. Adeparusi 100319475328460029508 100319475328460029508 No Department of Fisheries and Aquaculture Technology, Federal University of Technology, Akure, Ondo State, Nigeria. Department of Fisheries and Aquaculture Technology, Federal University of Technology, Akure, Ondo State, Nigeria.