Laboratory Evaluation of the Immune Response of Young Broiler Chickens Vaccinated Against Newcastle Disease Under Field Conditions

摘要: Abstract Four experiments were conducted to examine the efficiency of 4 different New-castle disease (ND) field vaccination programs. For all young broiler chickens obtained from breeder flocks regularly vaccinated against ND. The following programs tested: 1) at 1 day age; 2) and 20 days 3) 7 days, 4) 12 age. In experiments, 10 randomly chosen birds each 6 farms that commercially plus nonvaccinated control bled just prior separated into 2 groups based on birds’ mean NDV hemagglutination-inhibition (HI) titers. At various times after vaccination, sera assayed for HI titers then challenged with virulent establish resistance. Serologic challenge data indicated majority any one produced measurable refractory challenge. However, greatest serologic response best resistance clinical ND found in relatively low levels maternal immunity time initial receiving a booster