Abstract: In order to assess the performance of weaned piglets fed diets supplemented with different doses of Macleaya cordata extracts, this study selected 252 Duroc× Landrace×Yorkshire crossbred weaned piglets which were(35±2) d old each and with close weight and were randomly divided into seven treatment groups: a control group (I group, pigs fed with basal diet without any drug additives), five test drug groups (pigs fed with basal diet supplemented with different doses of Macleaya cordata extract with 0.337, 0.675, 1.35, 2.7 and 5.4 mg/kg total alkaloids expressed as sanguinarine + chelerythrine), and a positive control group (pigs fed with basal diet supplemented with 30 mg/kg chlortetracycline). The treatmeat period lasted for 28 d. Growth performance of the various treatment groups were measured at the end of the test. The results showed that compared with the other dose groups and positive control group, these two treatmeat groups of 0.675 and 1.35 mg/kg（P<0.05）had a significant improve on feed intake（P<0.05）and average daily gain（P<0.05）and reduction of piglet feed conversion（P<0.05）. At the same time, diets supplemented with different doses of Macleaya cordata extract can effectively prevent the incidence of piglet diarrhea. The results showed that the performance of weaned piglets fed diets supplemented with different doses of Macleaya cordata extracts and the economic efficiency were improved effectively. And the ideal dose is supplemented with 0.675 mg/kg dose of Macleaya cordata extract (total alkaloids expressed as sanguinarine+chelerythrine).

Key words: Macleaya cordata extracts; weaned piglets; phytobiotics