Available online at www.scholarsresearchlibrary.com Scholars Research Library European Journal of Zoological Research, 2014, 3 (1):81-85 (http://scholarsresearchlibrary.com/archive.html) ISSN: 2278–7356 81 Scholars Research Library Efficacy of different live Newcastle disease vaccines in broiler farms Masoud Hassanzade Makoui 1* and Adel Feizi 2 1 Department of Veterinary Medicine, Tabriz Branch, Islamic Azad University, Tabriz, Iran 2 Department of Clinical Sciences, Tabriz Branch, Islamic Azad University, Tabriz, Iran _____________________________________________________________________________________________ ABSTRACT 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. Keywords: Newcastle Disease, Live vaccine, broilers, HI test _____________________________________________________________________________________________ INTRODUCTION Newcastle disease virus is classified in Genus Paramyxovirus in Paramyxoviride family(1). This virus has RNAnon mutation characteristics. The virus contains a single-stranded genome that often causes to different variations with subtle differences in RNA phenotype and incorrect replication of the particles (2).Otherwise, these variations are not progressed under suitable selection conditions. It shouldbe pointed that the population of the Newcastle disease virus challenged in the farm is not clonal with the population of Newcastle disease virus used in the vaccine (2, 3).Selection pressure could change viral behavior. According to this study, some variations change virus pathogenicity and resistance to heat(4). Infectious virus (Virion) has a lipoprotein cover that it is essential for infection (5) and Ministry of Agriculture, Fisheries and Food, 1974. The proteins of virus coverage are specific in terms of genome. They are important for their antigens and they participation specificity of the host and range of virus’s pathogenesis(6).We can propose other characteristics of the virus by biological comparing of this virus with other viruses of Paramyxosvirus(4). Specifically, it is expected that Newcastle disease virus is stable based on geographical limit and time from antigen perspective(7, 8).Although variants are identified with monoclonal antibodies or analyzing sequences, polyvalent antiserum cannot detect strains easily. Newcastle disease virus usually is cultured in allantoic cavity epithelium in embryonated chicken eggs. Some strains kill the fetus(9). Also, virus grows in cell cultures with the birds and some mammalian cell origin. Some strains of virus replication and host cell destruction is shown that called cytopathogenicity(9, 10). Diagnosis of all strains of Newcastle disease virus cultured in cell is difficult (4).Newcastle disease virus agglutinates RBC of chicken (and sometimes RBC of other species). This stage is known as Hemagglutination and Hemagglutination inhibition forms the basis of conventional tests for the detection of antibodies of this virus in vitro and other serological tests are available. Different methods of