Comparative Efficacy of Five Different Brands of Commercial Newcastle Disease Lasota Virus Vaccines in Broilers

Five commercial LaSota strain Newcastle disease (ND) vaccines namely A, B, C, D and E were evaluated for their potency, efficacy, thermostability and influence on productivity in broilers. A 3-log10 difference of EID50 and two-to-eight fold difference of HA activity was found among the various vaccines tested. One hundred and fifty day-old broiler chicks were divided into six equal groups tagged as I, II, III, IV, V and VI. The birds in groups I, II, III, IV and V were actively immunized against ND on days 7 (eye drop method) and 21 (drinking water) using vaccines A, B, C, D and E, respectively. The birds in group VI served as unvaccinated control. The serum HI antibody response to five vaccines was determined 7, 14, 21 and 28 days post-vaccination. Fifteen birds from each group including unvaccinated control were challenged at day 35 with local virulent ND field isolate. The HI serum antibody profile and post-challenge mortality pattern revealed a dose-response relation between the virus content, humoral antibody response and clinical protection. To compare the heat stability, the vaccines were incubated at 4, 25 and 40C for a period of 24 hours. There was no remarkable reduction in HA titer, however slight dips (less than 2 logarithmic units) in EID50 values were found in all the vaccines. All the vaccines caused significant suppression in weight gain, leading to a poor performance in terms of feed conversion ratio (FCR) and European Efficiency Factor (EEF).