The present research work was undertaken to assess the immuno-modulatory effect of Garlic on different concentrations and Zinc Bacitracin on the antibody titers against ND in NDV vaccinated broiler chicks.

For this purpose 150 day-old broiler chicks were purchased from the local market and divided into 5 equal groups i.e. A (vaccinated, non medicated control), B (administered with ND vaccine and Zinc bacitracin), C (administered with ND vaccine "Lasota" and 1 g/kg Garlic), D (administered with ND vaccine "Lasota" and Garlic 5 g/kg), E (administered with ND vaccine "Lasota" and Garlic (10 g/kg). Each group comprised of 30 chicks. Group E was fed on a ration containing Garlic at the dose rate 10 g/kg of feed and given throughout he study period i.e. upto 42 days of age.

The comparative immuno-modulatory effects of Garlic and Zinc Bacitracin were worked out on the basis of GMT levels in ND vaccinated unmedicated birds alongwith the ND vaccinated, medicated birds. These titers were evaluated by using HA and HI tests on the sera of these experimental chicks. Other parameters i.e. morbidity, mortality, weight gain, FCR, postmortem findings, weight, size and texture of spleen, thymus, bursae and liver were also assessed in drawing the final conclusion. Data was analyzed statistically using one way analysis of variance and least significant difference (LSD) to find out the means of the experimental groups.

The birds that were, NDV vaccinated and Garlic 1 g/kg medicated had the highest body weight and showed best FCR. The birds NDV vaccinated and Garlic 5 g/kg medicated secured second position regarding weight gain and FCR among the three experimental groups (A, B and C). The birds from group B (Z.B. and NDV) had the higher body weight than group (A and C). Feed conversion ratio of group B was also found to be better than group A (NDV vaccinated, unrnedicated) and group C (NDV vaccinated and Garlic 1 g/kg medicated). None of the three treatments (Garlic, Z.B. and control) had any adverse effects on the weight size, and texture of lymphoid organs (bursa of Fabricius, spleen, thymus and liver). The birds belonging to group E (NDV vaccinated, Garlic 10 g/kg medicated) had shown the highest antibody titers on day 42. While the birds of group A (NDV vaccinated, unmedicated control) had the lowest antibody titers. Among the three experimental groups (B, C and D), the birds from group D had higher antibody titers as compared to other treatment groups. Whereas the group B had the higher antibody titers than the group C.