The effect of virginiamycin and avoparcin on body weight gain, humoral and cell-mediated immune response in Hubbard Cockerels was investigated. In all treated birds, body weight gain and liver weights were increased. A significant decrease in the weight of bursa of Fabricius was recorded in Cockerels fed on avoparcin treated ration. There was a significant decrease in serum concentrations of gamma globulins, humoral response to sheep RBCs, cutaneous reactions to purified protein derivative or heterophil and
ANTIBIOTICS AND IMMUNE RESPONSE OF CHICKENS
eosinophil counts in avoparcin treated group. Virginiamycin had a slight effect on humoral and cell mediated responses.