This study indicated that Amprolium 20% (Amidiostat) when used at recommended dosage levels (0.5 Kg/ton of feed did not interfere with the body weight gains of birds; did not have adverse effects on weights of lymphoid organs such as bursa of Fabricius, spleen, thymus, liver; did not interfere with the development of serum antibody in vaccinated or non-vaccinated and challenged birds; Amprolium 20% medication in feed had beneficial effects on serum antibody development; did not result in higher post-challenge mortality of vaccinated birds as compared to the non-medicated vaccinated control birds. however Sulphaquinoxaline when used at recommended dosage level (125 gm/ton of feed) did partially interfere with the weight of lymphoid organs such as bursa of Fabricius, spleen, thymus, liver and also interfere with the development of serum antibody in vaccinated or non vaccinated and challenged birds. The injection to baby chicks on first 4 consecutive post- hatching days with cyclophosphamide resulted in lower body weights, destruction of the bursa of Fabricius, poor antibody response of birds to vaccination against ND, and very high post-challenge mortality, UOfl challenge with virulent NDV.

The weight gain studies indicated that vaccinated and non-vaccinated birds on Amprolium 20% and suiphaquinoxaline medicated feeds had non- significantly higher body weights than those on non-medicated ration at 42 days of age. Amproliurn 20%, at recommended dosage level, had more beneficial effects on the body weights than the suiphaquinoxaline. These studies further indicated that vaccinated birds kept on Amprolium 20% medicated feed had significantly higher serum antibody titres on (lay 42 than the vaccinated non-medicated control birds. The serum antibody titres of vaccinated birds on Amprolium 20% medicated feed were significantly higher thai-i those fed sulphaquinoxaline at recommended dosage levels. From the results of this study it is concluded that long term use of Suiphaquinoxaline at recommended dosage levels moderately suppress the immune system of the birds. It is also observed that Amprolium 20% (Amidiostat) is not immunosuppressive drug when used at recommended dosage levels. It has rather beneficial effects on growth performance and immune response of birds. However there is a need for further investigations.