All
chickens were bled weekly for 35 days post-treatment. Body weights, thymus, bursa and spleen ratio
scores were determined at 21 and 35 days while body weight was determined weekly. The results
revealed non-significant differences in body weight between all groups compared to the control
group. Antibody titers against NDV also exhibited non-significant differences at third, fifth and
sixth weeks of the experiment between treated groups while they were significantly different from
the control group. At the fourth week, group C showed significantly different antibody titers from
other treated groups. However, antibody titers against IBV were significantly different in the fifth
and sixth weeks against the control group. Similar results were recorded with IBDV vaccine compared
to the control group while group C had significant differences in titers at 4, 5 and 6 weeks
post-vaccination. Lymphoid organs, namely thymus, bursa and spleen showed non-significant differences
between groups. This study showed that dietary supplement of black cumin seed at the
level of 1% or 1.4% would enhance immune responsiveness in broiler chickens.