Comparative efficacy of five different brands of commercial newcastle disease LaSota virus vaccines in broilers
2005
Abbas, T.
Study was to compare five major commercial NDV (LaSota strain) vaccines being used in Pakistan with respect to potency, efficacy, thermo stability and influence on production performance in broiler chicks. The representative vials of the live NDV LaSota strain vaccines namely A, B, C, D and E were procured from local market. The vaccines were assayed for 50% infectivity (EID50) and Haemagglutinative ability (HA). A 3-log10 difference of EID50 and two-to-eight fold difference of HA activity was found among the various vaccines. One hundred and fifty day-old broiler chicks were divided into six groups and managed separately. The birds in group I, II, III, IV and V were actively immunized against ND on day 7 and 21 using vaccines A, B, C, D and E respectively. The birds in group VI served as unvaccinated control. The scrum HI antibody response of the different vaccines was determined 7, 14, 21, 28 days post-vaccination. The birds (n 5) in all the groups including unvaccinated control was challenged at day 35 with local virulent field isolate. The Hl 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 degree C, 25 degree C, and 40 degree C 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).
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