title: Effect of difference doses of Newcastle disease vaccine immunization on growth performance, plasma variables and immune response of broilers.
abstract: BACKGROUND
  As a member of the Paramyxoviridae group, Newcastle disease virus (NDV) is the key causative agent of Newcastle disease (ND) that attacks chickens, turkeys and other avian birds. Surviving birds showed lower feed utilization, growth performance or egg production, which results in severe economic losses. The purpose of this study was to determine the effect of different doses of NDV immunization on growth performance, plasma variables and immune response of broiler chickens.
  
  
  METHODS
  A total of 480 one-day-old Arbor Acres broilers were randomly administrated with 0, 4, 6 or 8 doses of NDV at 12 d and 28 d, respectively. Each group consisted of ten replicates with 12 birds each. Growth performance and organ weight were recorded. Plasma concentration of glucose, total protein, cholesterol, triglycerides and nonesterified fatty acid was determined using commercial kits. The concentration of plasma corticosterone and insulin was measured using commercially available radio immune assay kits. Serum antibody titer and peripheral blood lymphocyte proliferation were also recorded.
  
  
  RESULTS
  The results showed that NDV decreased body weight gain (BWG), and increased Feed:Gain ratio at 1-21 d at all doses (P < 0.05). Plasma insulin concentration was lower in all immunization groups after the first immunization at 12 d (P < 0.01). The rest of the plasma indexes were not affected by NDV immunization, including glucose, total protein, cholesterol, triglycerides, nonesterified fatty acid, heterophil/lymphocyte ratio, as well as the proliferation of peripheral blood lymphocyte (P > 0.05). Compared with the control group, NDV treatment elevated NDV antibody titer at 10 d after the first inoculation (P < 0.05), and at d 5, 9 and 13 after the second inoculation (P < 0.05). Repeated NDV inoculation had no deleterious impacts on body composition at 42 d, and nutrient accretion rates at 8-42 d (P > 0.05).
  
  
  CONCLUSIONS
  In conclusion, NDV challenge decreased BWG and feed efficiency in earlier stage of growth. However, NDV treatment at 6 doses down-regulated the Feed:Gain ratio by 6.36 % throughout the whole growing period. These data suggest that appropriate lower doses of NDV inoculation increase feed efficiency of broiler chickens.
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi China ; College of Science, Nanjing Agricultural University, Nanjing, Jiangsu 210095 China.
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Wang
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi China.
authors.forename: Qinqin
authors.initials: Q
authors.lastname: Zhou
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi China.
authors.forename: Jing
authors.initials: J
authors.lastname: Shen
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi China.
authors.forename: Junhu
authors.initials: J
authors.lastname: Yao
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi China.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Yang
keywords: Broiler; Immune response; Metabolism; Newcastle disease vaccine