Abstract: To study the effects of free gossypol (FG) in the diets on immunity in the starter period of HISEX layers, 360 brown shell HISEX layers of 1 day of age were assigned randomly to four groups with three pens per groups and 30 chicks per pens. The chicks in control group (group Ⅰ) were fed with the basal diets and the chicks in other groups were fed the diets containing free gossypol, 70,105 and 140 mg/kg, respectively. The trial lasted for 6 weeks from 1 to 42 days old. On 14, 28 and 42 days, indices of immune organs and the level of cytokines in the sera were measured. Sera HI of Newcastle disease was detected once a week. The results showed that the organ index of bursa of fabricius, thymus and spleen were not influenced by the level of FG in the diets.Different levels of free gossypol had no significant effect on ND antibody titre of HISEX layers. Different levels of free gossypol decrease levels of sera cytokine IL-2,IL-4 and IFN-γ. It was concluded that up to 140 mg/kg of FG had no significant effect on immune organ index and titer of Newcastale disease. But it could decrease level of serum cytokine on 42 days.

Key words: free gossypol; immunity; immune organ index; cytokines