This study was carried out to evaluate the effect of supplementing different concentrations of N-acetyl-cysteine in the extender on cryo-preservation quality of chicken semen. The fresh semen samples from Anka breeder chickens were collected and diluted with two separate extenders(A and B) each adding different concentrations(0.013 0 and 0.002 6 mol/L) of N-acetylcysteine. The diluted semen samples were subsequently cryo-preserved and the preservation time, survival index and deformity rate were determined....