الفهرس 
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Abstract
Recent studies have been conducted to modify semen extenders for protecting buffalo sperm during freezing- thawing process. This study aims to determine (1) the effect of various concentrations of soybean lecithin (SL) as an alternative for egg yolk (EY) in buffalo bull semen extender on pre-freeze and post- thaw sperm quality characteristics. (2) the effectiveness of type and concentration of different non-permeable [egg yolk (EY), soybean lecithin (SL) and cholesterol-loaded cyclodextrins (CLC)], permeable [glycerol (G), di-methyl sulphoxide (DMSO) and ethylene glycol (EG)] and antioxidative [butylated hydroxytoluene (BHT)] cryoprotectants on the functional sperm quality in buffalo bulls pre- and post-freezing extended with egg yolk (TCFYG) and lecithin (TCFGL) - based extenders. (3) The influence of different cryoprotectants on fertility rate of buffalo cows inseminated with frozen-thawed buffalo bull semen extended in TCFYG (control) and TCFGL extenders. Four buffalo bulls belonging to the Abassia Frozen Semen Center, General Organization for Veterinary Services were used in this study. The substitution of egg yolk into TCFG with 1.0% SL and 1.5% SL during equilibration period significantly ameliorated the maintenance of all studied semen characteristics compared to control. All studied parameters (progressive motility, viability, morphology and acrosome as well as plasma membrane integrities) in semen containing different concentrations of DMSO, EG, CLC and BHT were significantly (P ˂ 0.01) higher in lecithin (TCFGL)-than in egg yolk (TCFYG) - based extenders in pre-freeze and post-thaw stage of cryopreservation. The interaction between used extender and semen quality parameters at the best concentration of DMSO (3.0 -4.0%), EG (3.0- 4.0 %), CLC (1.5 – 2.25 mg / ml) and BHT (0.5-2.0 mM / ml) depending upon types of used extenders and stages of pre-and post-freezing process improved (P ˂ 0.01) semen variables. However, greater concentrations of different cryoprotectants had a detrimental (P ˂ 0.01) effect compared with the control with all extenders evaluated. Artificial insemination of post – thawed buffalo semen diluted with TCFGL produced acceptable fertility rates compared with semen diluted with TCFYG (66.67 vs 50.00 %). Combination of cryoprotectants revealed better fertility rate in inseminated buffalo cows. Combination of 3 different cryoprotectants [ (2.0% DMSO, 1.5% EG and 1mg / ml CLC)] to the SL – extender improved conception rate (60.00%) and with substitution of CLC by BHT (0.75 mM / ml) in this combination of cryoprotectants show a significant (P ˂ 0.01) increase in conception rate (75.00%).