This research was carried out in two experiments. In first experiment, three different levels of vitamin C (0, 50 and 100 mg/kg feed) were added the diets based on corn, and the effects of the diets on egg yields, blood vitamin levels, T-lymphocyte percentage, plasma cell count in spleen and antibody titers against the vaccine of Newcastle disease were investigated for one year. Total of 648 laying hens were used in this experiment. The group fed the diet added 50 mg/kg vitamin C, produced less egg and fed more feed for one kg egg than other groups. There were no obvious differences among groups at the antibody titers, the ratio of T-lymphocyte and blood vitamin C levels. In the second experiment twentyfour chiks for each group were supplied by hatching eggs from the hens used in experiment I in order to investigate maternal immunity. Antibody titers were determined at day 2, 7 and 10. At same day, for histologic investigation, blood and some lenfoid tissue samples from spleen, bursa Fabricii, tymus and ileum were taken at same days. The effects of different vitamin C levels were not significant on the antibody titers and histologic results.

This research was carried out in two experiments. In first experiment, three different levels of vitamin C (0, 50 and 100 mg/kg feed) were added the diets based on corn, and the effects of the diets on egg yields, blood vitamin levels, T-lymphocyte percentage, plasma cell count in spleen and antibody titers against the vaccine of Newcastle disease were investigated for one year. Total of 648 laying hens were used in this experiment. The group fed the diet added 50 mg/kg vitamin C, produced less egg and fed more feed for one kg egg than other groups. There were no obvious differences among groups at the antibody titers, the ratio of T-lymphocyte and blood vitamin C levels. In the second experiment twentyfour chiks for each group were supplied by hatching eggs from the hens used in experiment I in order to investigate maternal immunity. Antibody titers were determined at day 2, 7 and 10. At same day, for histologic investigation, blood and some lenfoid tissue samples from spleen, bursa Fabricii, tymus and ileum were taken at same days. The effects of different vitamin C levels were not significant on the antibody titers and histologic results.