| Dissertation note |
The aim of the study was to compare five major commercial NDV (LaSota strain) vaccines being used in Pakistan with respect to potency, efficacy, thcrnioslability and influence on production performance in briolier 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 (BID50) and Haemagglutinative ability (HA). A 3-log10 difference oF EJD50 and two- to-eight fold difference of HA activity was found was found among the various vaccines. Onc hundred and fifty day- old broiler chicks were divided into six groups and managed separately. The birds in group I, II, Ill, 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 serum 1-Il antibody response of the different vaccines was determined 7, 14, 21, 28 days post-vaccination. The birds (n= 15) in all tile groups including unvaccinated control was challenged at day 35 with local virulent field isolate. The HI serum antibody profile and post-challenge mortality pattern revealed a dose- response relation between the virus content, humor-al antibody response and clinical protection. To compare the heat stability, the vaccines were incubated at 4C, 25CC and 40C for a period of 24 hours. There was no remarkable reduction in I IA liter, however slight dips (less than 2 logarithmic units) in LID50 values were found in all the vaccines. All the vaccines caused siginifcant suppression in weight gain leading to a poor performance in terms of Feed Conversion Ration (FCR) and European Efficiency Factor (EEF)
|
