A comparative study on the immunogenic and protective properties of the V4, Hitchener BI, and LaSota Newcastle disease vaccines in commercial chickens

English

A commercial V4 vaccine was compared with the conventional Hitchener BI (HBI) and LaSota Newcastle disease (ND) vaccines for seroconversion and ability to protect commercial chicks against artificial challenge of ND virus. In the two experiments, groups of broiler and replacement pullet/cockerel chicks were vaccinated orally with HBI at 2 weeks and LaSota at 6 weeks or V4 at 2 and 6 weeks. In addition, another group of replacement chicks was given V4 at 2 weeks and LaSota at 6 weeks. Groups of unvaccinated controls were included in both experiments. At day-old and weekly intervals, semen samples were collected from all.groups and tested for ND virus antibody titres. using the micro haemagglutination-inhibition test. Eight to '15 birds from the groups of birds were challenged with a velogenic ND virus strain at 5 and •9 weeks old. Due to interferepce of maternal antibodies, primary vaccination with I-IBI or V4 at 2 weeks generally resulted in low seroconversion, although replacement chicks HBI caused an increase of geometric mean titre (GMT) of 1093.71 ± 1.31 at 2 weeks to 5.39 ± 2.10 at 3 weeks. Broiler chickens given LaSota at 6 weeks showed increasing titres from 1.30 ± 1.59 to a maximum of 3.40 ± 1.20 at 8 weeks, but tèll rapidly to 1.86 ± 2.06 at 9 weeks. Replacement chicks given LaSota showed rising titres from 1 .86 ± 2. 1 to 6.94 ± I .48 at 9 weeks. In contrasts the GM Ts in V4-vaccinated birds rose from 1.67 ± 2.08 at 6 weeks to only 2.53 ± 2.44 at 8 weeks. Challenge tests at 5 weeks showed that replacement chicks vaccinated with HBI were better protected (45.7 % ± 27.00) than V4 - vaccinated chicks (27.14 % ± 28.60; P<0.05). Birds challenged at 9 weeks following revaccination with LaSota showed a significantly (P<0.05) higher survival rate (77.14 % ± 15.84) than those revaccinated with V4 (35.70 % ± 28.00) and unvaccinated control (41.63 % ± 30.37). Curiously, unvaccinated control chicks challenged at 5 weeks showed the highest survival rate of 60.00 % ± 20.95. Broiler birds challenged at 9 weeks after LaSota reïvaccination also showed

Aning, K. G.; Brewoo, J. N.