Abstract: Compound traditional chinese medicine (CTCM) had been selected successfully in the test,which was identified as the best anti-bacterial effect against colibacillosis in chickens. CTCM was conducted to the development of ultrafine powderthe common fine powder,the particle size of ultra-fine powder was smaller and distributed more regularly.Only fragment of tissue was observed as tissue cell was broken in ultra-fine powder while the tissue cell of common fine powder was still intact and the primary profile could be observed (e.g. stone cell and catheter) in common fine powder.The dissolution test showed that the dissolution of citric acid,main active component of Ebony,was increased by 78.6 percent under the same condition. Comparing the inhibition effect against avian E.coli,the ultra-fine powder through simple extracted showed a better antimicrobial behavior than that extracted from common fine powder of CTCM. ②The experiment in which the diseased chicken were treated by feeding with CTCM,indicated that the mortality of the high and middle dose groups of ultra-fine powder was significantly lower than the infected control group (P<0.01),however,the groups of the low ultra-fine powder dose and common fine powder had no significant difference compared to the infected control group (P>0.05); in the high dose group of ultra-fine powder,the mortality rate was significantly lower than the common fine powder group (P<0.05),and the cure and effective rate also showed significantly difference between the two groups (P<0.05).

Key words: Colibacillosis; Chinese herbs; ultra-fine powder; dissolution; efficacy