RESUMEN
Newcastle disease is one of the most important causes of economic losses in the poultry production and can he resulted in high mortality. Antibody detection is also an important tool for assessment of the immunity against the disease. In the present study a trial was conducted to evaluate the effect of an immune stimulator[Echinacea purpurea] on antibody production against Newcastle disease vaccine. 450 one day old broiler chicks were divide into five groups of three repeat each. For three weeks from day one various doses of Echinacea purpurea extract was prescribed to four treatment groups and to the fifth group placebo in water was prescribed. All groups were vaccinated on days:11, 19, 38. Subsequently. serum samples were collected at days 10. 25, 34.52 of post vaccination from 21 chicks of each group [4 samples of each repeat] and were tested for Newcastle antibody titers by HI test. This experiment showed that the use of Echinacea purpurea extract with the rate of 29, 75Mg per kilo body weight per day had better effects on antibody titers and significantly increased between control group arid treatment groups [p<0.01]. It is also revealed that the use of Echinacea purpurea induces FCR improvement and mortality rate was decreased significantly [p<0.01]