Increased doses of La Sota vaccine increased Newcastle disease antibody response significantly in broiler chickens (Gallus gallus domesticus)

ABSTRACT This study investigated if increased doses of La Sota vaccine can increase antibody response to Newcastle disease without any serious adverse effect on the bursa. One hundred broilers aged four weeks were randomly assigned into four groups of 25 each: ZD, each drenched with phosphate-buffered saline, SS, DD and TD broilers were each drenched with single, double and triple dose of La Sota vaccine, respectively. The broilers were examined for signs and lesions. At weekly intervals, serum samples were collected post-vaccination (PV) and assayed for haemagglutination inhibition antibody. Groups DD and TD antibody titres were significantly (p？<？0.05) higher than that of the SD on day 21 PV. But there was no significant (p？>？0.05) difference between titres of DD and TD groups. Groups DD and TD geometrical mean titres were more than two times higher than that of SD group on day 21 PV. The bursa of all the vaccinated groups appeared reduced in size, with mild depletion of lymphocytes on day 10 PV. Generally, the integrity of the bursa was intact. This suggests that doubling the dose of La Sota vaccine may be considered in improving the performance of the vaccine in the control of velogenic Newcastle disease