The Thai Journal of Veterinary Medicine


One hundred and sixty eight, 5-week-old, male, layer-type chickens were divided into 7 groups, 24 birds in each. Group1 was a non-vaccinated control. Groups 2, 3, 4, 5, 6 and 7 were vaccinated with inactivated, lentogenic strain of Newcastle disease (ND) by subcutaneous injection. All birds were challenged when 11-weeks-old. They received a local strain of virulent ND virus by the oral route. All birds were weighed when 5, 11 and 13-weeks-old. Blood samples were collected at 5, 7, 9, 11 and 13-weeks-old. The sera were tested for ND antibody by the Hemagglutination-Inhibition (HI) test. The result revealed the HI antibody titer in each group after vaccination was highest at 9-weeks. After challenge, the morbidity and mortality rates amongst the vaccinated groups were not significantly different (p>0.05) while all birds in the non-vaccinated group were dead within 10 days.

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