A total of 60 one-day old Ross broiler chicks were used in this study. The birds
were divided into four groups. The first group A was vaccinated against IBD with a Cevac
IBD L vaccine at one-day old by intra-yolk sac method (lYS) with a dose of 0.5ml using a
(1ml) syringe, whereas the second group B was vaccinated against IBD with the same
vaccine at 14 days of age by drinking water method (DW). The third group C and fourth
group D were considered as a positive and negative control respectively . On day 35, the
birds were weight and killed to collect blood samples and lymphoid organs were
removed and weight to study the effects of (lYS) rout on body weight , lymphoid organ
weights and the humeral immune response to IBD vaccine which measured by ELISA
test. The results showed significant differences at (P≤0.05) in body weight of group A, in
addition significant (p<0.05) increase in the all lymphoid organs weight , Bursa of
fabricius (BF) was 1.643 a ±0.066 in group comparison with other groups which had been
recorded 1.102 b ±0.022, 0.850 c ±0.067 in group B and C respectively. Group B indicated
that was a significant decrease at (p<0.05) in the weight of of spleen which was 1.102 b
± 0.022 in comparison to control groups. With regard to serological test, bird from group
A recorded higher Ab titer 24038 a± 685 compared to those of other groups , and this
increment was statically significant (p<0.05), however both group A and B revealed a53

significant differences( p <0.05) from the control groups. Generally the results indicated
that intra-yolk sac method was highly effective rout of IBD vaccine administration