The present invention is to provide a safe antidiarrheal agent and a method for suppressing diarrhea by which an efficient antidiarrheal effect is achieved without using antibiotics or synthetic antibacterial agents that have been conventionally used against infections in livestock and poultry. Antibiotic-resistant pathogenic infections can also be prevented and treated by the present invention. The antidiarrheal agent for livestock and poultry comprising heat-killed bacteria of Enterococcus faecalis EC-12 (FERM ABP-10284) or a treated product thereof as an active ingredient is orally administered to livestock and poultry, particularly to breast-feeding sows and piglets around the weaning period.本發明係提供一種安全之下痢抑制劑及抑制方法，其無需使用如先前般用於家畜、家禽感染症中之抗生物質或合成抗菌劑，便可發揮有效之下痢抑制劑效果，又，亦可預防或治療對耐抗生物質具有耐受性之病原性感染病。；將含有糞腸球菌(Enterococcus faecalis)EC－12(IFO 16803及FIRDI BCRC 910295)之加熱處理的死菌體或其處理物作為有效成分的家畜、家禽之下痢抑制劑，經口投予家畜、家禽，特別是經口投予授乳期之母豬及斷乳期前後之仔豬。
