الفهرس 
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Abstract
This study aimed to examine the effect of addition (leptin and melatonin) as antioxidants to extender Tris-egg yolk (TEY), without supplementation (control), Leptin was supplemented to the extender at levels of (10,20 and 50 ng/ml) and Melatonin was supplemented to the extender at levels of (10-3M, 10-6M and 10-9M) (7 group treatments). Five sexually mature buffalo bulls (4-5 years) were used in this study. Semen was collected from the experimental bulls twice aweek for 4 weeks Semen was equilibrated at 50c for 2,4,8 and 12 hours and storage at -196oC for one month. Frozen straws for each extender treatments were thawed at rates 37°C/30 sec, Physical semen characteristics including motility, dead and abnormality of spermatozoa were determined in post- diluted, post-equilibrated (at different times) and post-thawed semen at thawing rate, Activity of (AST) , (ALT) and (LDH) were determined in post-freezing,Acrosome damage and conception rate. The main results can be summarized as follows: The highest percentage of Progressive sperm motility,Dead and Abnormal sperm (P<0.05)in post-dilution and post-equilibration on semen extended with leptin (20 ng/ml )and melatonin (10-3M), while TEY (0) showed the lowest percentage. Also,The highest percentage of Progressive sperm motility,Dead and Abnormal sperm (P<0.05)in post-thawing on semen extended with leptin (20 ng/ml )and melatonin (10-3M), while TEY (0) showed the lowest percentage,The lowest percentage of acrosome damage of spermatozoa in post-thawed with incubation time ( 0h ) and the highest with incubation time ( 2h ). The lowest percentage of activity enzymes (ALT,AST,LDH) were (P<0.05) in post-thawing on semen extended with leptin (20 ng/ml )and melatonin (10-3M), while TEY (0) showed the lowest percentage. Conception rate was higher for semen extended with antioxidant supplementation LE (20 ng/ml) and ME (10-3M) (91.6 and 75.0%) as compared to that extended with TEY without antioxidant supplementation (66.6%). In conclusion, the obtained results revealed that adding 20 ng/ml of leptin and 10-3M of melatonin to Tris-based extender had beneficial effects on motility, livability and normality of buffalo spermatozoa in diluted, equilibrated and thawed semen as compared to un-supplemented semen. These improvements were associated with increasing conception rate of buffalo cows which can be helpful for artificial insemination.