Performance, Blood Biochemistry Parameters And Immune Function To Newcastle Disease Vaccine In Broiler Chickens

Two experiments were conducted to determine the impacts of different levels of Newcastle Disease Vaccine (NDV) on performance, metabolism, immune responses and body nutrient contents in broiler chickens, in order to a better understanding of responses of NDV challenge and its mechanism in broiler chickens, which help in optimizing immunization program and developing theory of immune stress and reprogramming of metabolism. Eight-day-old broilers (480) were allocated to four groups, 120 broilers in each and inoculated with 0, 4 NDV, 6 NDV, 8 NDV on days 12 and 28, respectively. Each treatment had six replicate cages of twenty broilers per replicate cage.Experiment one was conducted to determine the effects of different levels of NDV on performance and blood parameters of broilers.No significant difference in feed intake was found between the control and NDV-treated birds during the experiment. However, birds inoculated with NDV had lower average weight gain and feed conversion ratio at days 8-21 compared with the control birds (P<0.001). 4 NDV and 6 NDV inoculation significantly reduced feed intake: body weight gain at days 21-42 and days 8-42 (P <0.05) while BW gain had little difference among all groups (P>0.05). Except for feed intake: body weight gain in 8 NDV birds was markedly higher than 6 NDV birds at days 8-42, all growth parameters among NDV-treated chicks did not differ significantly in each experimental period. After first inoculation at 12 d, plasma CS level was higher in 8 NDV, but plasma insulin levels were lower in all immunization groups (P<0.01). The other physiological responses to NDV, such as glucose, total protein, cholesterol, triglycerides and nonesterified fatty acid, were unaffected after two inoculations. The results indicate that NDV reduced broilers growth performance in earlier period after first inoculation while appropriate NDV levels (4 NDV,6 NDV) improved feed conversion ratio in late period and the whole growing period. A high level of NDV could alter neuroendocrine, which resulted in immunological stress and tended to decrease body weight gain, but had no effect on plasma metabolite profiles.Experiment two to study the effects of different levels of NDV on immune responses and carcass contens of broilers.No significant differences were observed among groups for relative organ weights (spleen, thymus, Fabricius and liver) after each immunization and the proliferation of peripheral blood lymphocytes in response to lipopolysaccharide (LPS) and concanavalin A (ConA) after the second immunization on day 28. At 6 h and 12 h post the second inoculation, H/L ratios of the broilers in 6 NDV group were higher than the control (P<0.05). Compared with the control group, there was an improvement (P<0.05) in antibody titer to NDV on day 10 after the first inoculation of the vaccine and on days 5, 9 and 13 after the second inoculation. Repeated NDV injection had no deleterious impacts on the body composition (water, protein and lipid content) on day 42 and nutrient accretion rates at days 12-42. The results suggest that NDV injection did elicit a robust specific humoral immunity but not cell-mediated immunity. A high level of NDV injection resulted in no reduction in muscle accretion or increase in body fat deposition in broilers, even though 8 NDV was administered twice during days 8-42.In conclusion, NDV reduced broilers growth performance in earlier period while an appropriate NDV level improved feed conversion ratio in late period and the whole growing period. A high level of NDV injection could alter neuroendocrine, which resulted in immunological stress. It did improve NDV antibody titer but not cell-mediated immunity, resulting in no reduction in muscle accretion or increase in body fat deposition in broilers, likely due to not induce the reprogramming of metabolism.