Evaluation on efficacy of some infectious bronchitis virus vaccination schedules in preventing respiratory disease for Noi chickens

Abstract

The objective of this study was to evaluate the efficacy of some infectious bronchitis virus vaccination schedules in preventing respiratory disease for the Noi chickens. The experiment was conducted by 3 experimental groups which were arranged randomly, each group raised 500 chickens
taking from the parent flock that was vaccinated by the IBV vaccine. Monovalent vaccine, Cevac Bron 120 L, was vaccinated for the chicks at 3 days of age and repeated for the second time after 3 weeks in group 1. Combination vaccine, Cevac Vitabron L, only vaccinated once at the 3-day-old chicks in group 2. The chicks in control group were not vaccinated. The studied results showed that the chicken antibody titers after vaccination in group 1 reached the protection level at 52 days old and maintained a high level up to 87 days old (nearly finishing phase), while the protection level of the chickens in group 2 was only equivalent to the chickens in group 1 up to 52 days and GMT of the chickens at 87 days old was 4 times higher than before, indicating that the chickens were infected with respiratory disease. The rate of chickens that suffering severely with respiratory disease recorded 3 points and the mortality rate of chicken from 61 days old to the finishing phase in group 1 which were lower than those of group 2 and control group. Thus, the protection results of chicken in group 1 were better than those of group 2 and control group. Even though the manufacturers recommended that only one vaccination for the combination vaccine, re-vaccination for the Noi broiler flocks (local
chickens) is essential because the time of raising Noi broiler chickens is longer