Abstract
Two groups, 1 and 2, of broiler chicks were inoculated with avian infectious laryngotracheitis live virus vaccine at the age of 4 and 14 days, respectively. Mild reaction was noticed, but disappeared by 7 days after inoculation. Mean neutralizing antibody titer was 0.2-0.7 in group 1 and 0.5-1.1 in group 2 at the age of 40-70 days.
There was a relationship between the neutralizing antibody titer and the rate of prevention of chicks from infection.
When that titer exceeded 1.1, this rate was more than 80 per cent.
