The aim of the present work is to study immunomodulating effect of gentamicin on broiler chickens vaccinated against Newcastle virus at 18 days and challenged with a virulent strain of ND at the 30 th day of age.Three groups of one day old Hubbard chicks each of 30 birds were used in this study.Chicks of the 1 st group received 10 mg gentamicin /kg b. wt and those of the 2 nd group were given 20mg...