There are few studies performed for investigating the roles of different ratio and cryoprotectants with dithiothreitol or sucrose on sperm motility characteristics and antioxidant capacities of post-thawed bull spermatozoa. The objectives of this study were to compare glycerol (G) and ethylene glycol (EG) at different concentrations as cryoprotectants and dithiothreitol (D) or sucrose (S) (with/without) as antioxidants in Tris extender for cryopreservation of bull semen. Twenty-four ejaculates obtained from
three bulls were included in the study. Each ejaculate was split into four equal aliquots and diluted using both of the Tris extenders with glycerol (5% or 7%) or ethylene glycol (3% or 5%). After that, each extenders were split into three equal aliquots and diluted using both of the dithiothreitol 5 mM or sucrose 25 mM, and control (without additives) was cooled to 4 C and frozen in 0.25-ml French straws. when compared to control, different doses cryoprotectants and antioxidants addition no significantly increased the
percentages of post-thaw sperm progressive and motitilities, acrosome abnormality and plasma membraneintegrity (P > 0.05). However, EG3 + Syieldedthegreatest percentages of thetotal abnormality (P < 0.05). As regard to antioxidant activities G7 and EG5 led to lowest MDAactivity with orwithout D orS but, these results were not supported to the GPx activity (P < 0.01). The sperm motion characteristics such as VAP,VCL, ALH and BCF gave significantly different results (P < 0.05). When compared the DNAi ntegrity, different doses cryoprotectants without antioxidants addition significantly increased the percentages of the tail intensity and tail moment (P < 0.05). There were no significant differences observed in non-return rates among all treatment groups (P > 0.05).