Newcastle disease is a contagious disease that affects on many domestic and wild avian species. Newcastle has a negative-sense, single-stranded genome. The aim of present study was to compare efficacy of Newcastle disease’s live vaccines (Biovac, Clone and LaSota) in broilers using HI method. In this survey we used 1500 broilers from 3 different identical farms. We used Biovac, Clone and LaSota vaccines in farms No. 1, 2 and 3, respectively as dissolved in drinking water on days 8, 22 and 36. At 50 days of age, 20 blood samples from each farm were taken. Samples were transferred to the laboratory. Finally, HI test was done on sera and antibody levels in the sera were measured. There was significant difference between groups from aspect of titer resulted from LaSota and two others (P<0.05). Also, data showed that there is no significant difference between groups Clone and Biovac from aspect of titration. So, authors suggest use of LaSota as the most effective vaccine.
