الفهرس 
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Abstract
The present study aimed to investigate the effect of different semen extenders and additives on ram semen freezability. Semen samples were collected from ten mature Barki rams using artificial vagina twice /week /3 months (February : April). Only good quality semen samples were pooled and diluted with different extenders (tris, shotor, milk &BullXcell®) & different additives : I- Sugars (25 or 50 or 75 mM of sucrose, trehalose and raffinose). II- Antioxidants (5 and 10 mM of cysteine and glutathione or 50 and 100 mM of taurine). III- SDS (0.01%, 0.02 % and 0.03%). IV-Caffeine (1 mM, 2 mM & 4 mM). Pooled semen samples subjected to cooling then cryopreservation in liquid nitrogen. After thawing (370C /30 sec) frozen semen was evaluated for motility, viability, the integrities of membrane, acrosomal and DNA. Then the activities of ALT, AST, ALP and TAC were estimated. The obtained data revealed that : BullXcell® recorded the highest significant post thawing sperm parameters as compared with other extenders. Sugar addition to the freezing extenders (tris or shotor) resulted in a significant increase in semen quality, biochemical parameters and DNA integrities of post thawed semen ,where the best concentration was (75mM) as compared to the control of tris. While 50 mM of Sucrose or trehalose and 25 mM of raffinose were the best concentration used with shotor extender. Supplementation of tris with Cysteine at 10 mM resulted in the highest post thawing motility (58.75 ± 1.25%) when compared with the control (47.50 ±1.67 %).While Taurine at 100 mM concentration resulted in the highest viability index (178.75 ± 2.60) . Regarding the acrosomal and membrane integrities, taurine at 50 mM was the best concentration (14.00 ± 1.15% and 44.25 ± 0.63 %, respectively). Glutathione and taurine addition resulted in significant increase in DNA % when compared to the tris control group (95.38 ±0.48). AST activity (36.37 ± 1.24 U/L) and ALT (47.63 ± 1.66 U/L) was significantly lower upon the addition of (5 mM) cysteine (P < 0.05), and increased in TAC (3.79 mM/L) when compared with the control tris (1.09 mM/L) and other supplemented groups. Supplementation of Shotor extender with 5mM glutathione significantly improved (P > 0.05) the post thawing sperm motility (61.67 ±1.68%) as compared to the control shotor extender (46.67 ±2.45%). Taurine (50 mM) was the best one that improved (P > 0.05) sperm viability index as compared to the control respectively (180.83 ± 0.83, 145.83 ± 2.21). The acrosomal defects were significantly decreased (P> 0.05) in glutathione 10 mM (9.00 ± 1.16%) as compared to the control (21.00 ± 0.58%). The membrane integrity was shown to be significantly improved(P > 0.05) than the control (35.33±0.88%) when 5mM cysteine & 10 mM glutathione were used (47.00 ±1.16% and 46.33 ± 1.21%, respectively). A significant increase (P> 0.05) in the DNA integrity % (98.51 ±0.42%) was recorded when 50mM taurine was added to Shotor extender. Supplementation with taurine (50 mM) was the best one that significantly (P> 0.05) improved the enzyme leakage (AST, ALT, and ALP) and the TAC activity of frozen -thawed ram semen samples as compared to the control. Supplementation of the shotor extender with 0.02 % sodium dodecyle sulfate (SDS) led to significant improvement of the post thawed ram semen motility (61.66 ± 1.67%, 50.00 ± 1.67%) viability index (176.67 ± 2.21, 163.33 ± 2.21 ) acrosomal defects (18.67 ± 0.88 % , 22.23 ± 0.58%) and membrane integrity (44.67 ± 1.46 %, 39.00 ± 0.58 and reduced the enzyme leakage when compared with the control. Caffeine supplementation at 2mM to shotor extender resulted in the highest post-thaw motility and viability index (63.33 ±1.67 % and 176.67 ± 2.21, respectively) compared with control. Finally : Data revealed that BullXcell® extender can be successfully used as ram semen freezing extender. Supplementation of shotor extender with 50 mM of (sucrose or trehalose) or 25 mM of raffinose successfully improved the post thawing quality of Barki ram semen. 50 mM of the antioxidant taurine was the best concentration that improved post thawing ram semen quality. 0.02% SDS can be used to maintain rams semen membrane integrity after thawing. Caffeine can be used at 2mM dose to increase post thawing sperm motility and viability without affecting the acrosome integrity.