This project was designed to investigate the effects of two anticoccidials Ampisol 20% and Esb3 30% with and without supplementation of vitamins (A, D3, E and K3 as "Symodek") on the immune system of broiler chickens. To evaluate such effects the parameters used for study were; effects, on the weights of immuno regulatory organs (bursa of Fabricius, thymus, spleen and liver), organ body weight indices, histopathology of primary lymphoid organs (bursa of Fabricius and thymus), total and differential leukocytic counts, total serum protein, albumin globulin ratio and immune response to Newcastle disease virus vaccination. A total of 120 chicks, divided into 5 equal groups viz A to E were reared for 42 days. Groups A, B, C, and D were medicated with, Ampisol 20%, Ampisol 20% + Symodek, Esb3 30%, and Esb3 30% + Symodek, respectively while group E was kept as control(no drug medication). All the birds were vaccinated with ND virus vaccine on day 7th and day 2 1st. All the medication, was done through drinking water at the recommended prophylactic dosage levels.

The study revealed that Ampisol 20% had favourable effects on the weights of immunoregulatory organs, and organ (bursa of Fabricius, thymus, spleen and liver):bodyweight indices. Esb3 30% had negative effects on these parameters.

Histological studies of primary lymphoid organs (bursa of Fabricius and thymus) revealed no detrimental effects of different medications except in birds of group C and D given Esb3 30% or Esb3 30% + Symodek, where slight degenerative changes were noted in bursae and thymi.

On day 42 the mean TLC values were slightly lower in birds medicated with Esb3 30% as compared to birds which received Ampisol 20%. On day 42 the mean lymphocytic percentages were higher in groups medicated with Arnpisol 20% as compared to those given Esb3 30%. Vitamins supplementation exerted favourable effects on TLC and DLC values. This study further indicated that mean total serum protein (TSP), mean serum albumin, mean serum globulin and mean A/G ratios were higher in birds medicated Ampisol 20%, than those medicated Esb3 30%. Vitamin supplementation had augmenting effects on these values. On day 28, 35 and 42 the antibody titres in birds medicated with Ampisol 20% were higher than those given Esb3 30%. Vitamin supplementation exerted augmenting effects on the antibody titres.

It is concluded that Ampisol 20% had no immunosuppressive effects rather it exerted favourable effects on the weights of immunoregulatory organs, rpp albumin, globulin, A/G ratio, DLC and HI antibody titres against Newcastle disease virus. Esb3 30% moderately depressed the aforesaid components of immune system. The present study also revealed that vitamins (A, D3, E, K3) supplementation to anticoccidials improved the immune response of birds. However, there is a need for further investigation in this regard, with special reference to immune system of broiler chickens.