The present invention discloses a use of a colicin Ib and a microorganism expressing the colicin Ib, to improve animals intestinal microflora, and an effect of improving the growth efficiency and the feed-to-meat rate is obtained. Accordingly, the colicin Ib and the microorganism expressing colicin Ib can be used as a meat-growth agent or as effective gradient for a composition for promoting growth of animals or improving intestinal microflora.本發明係揭露一種將大腸桿菌素Ib或能夠表現大腸桿菌素Ib之微生物係能夠改善動物腸道內菌相,而能具有提高動物生長效率及換肉率之功效。據此,本發明所揭大腸桿菌素Ib或能夠表現大腸桿菌素Ib之微生物係能用於作為增肉劑或促動物生長、改善腸道菌相之組合物的有效成份。
