Abstract: In order to effectively prevent broilers from ascites and improve the raising rate, broilers are administered with a composition containing quinone(s) represented by the following chemical formula as an active ingredient: ##STR1## wherein Y and Z represent H, CH.sub.3, or one covalent bond of a double bond between C.sup.1 and C.sup.2, and n represents an integer of 1-11 in the chemical formula(I).