الفهرس 
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Abstract
The experimental work was carried out at physiology and biotechnology lab, in Animal Production Department, Faculty of Agriculture, Mansoura University, in cooperation with Animal production Research Institute, Agricultural Research Center, Egypt, during the period from September 2016 till August, 2017. This study aimed to evaluate the effect of supplementation of selenium nano-particles or A. harveyi leaves extract with different concentrations to bull semen extender on sperm characteristics, chromatin damage, ultrastructure changes and apoptosis of spermatozoa, total antioxidant and lipid peroxidation in seminal plasma as well as fertility rate of cryopreserved bull semen. Five healthy, fertile Friesian bulls were used, and the ejaculates were obtained using an artificial vagina. Semen of all bulls were pooled and diluted in a tris-yolk fructose (TYF) extender supplemented with Se-NPs (1st experiment) or methanol extract of A. harveyi leaves (2nd experiment) at concentrations of 0 (control), 0.5, 1.0 and 1.5 µg/ml for a final sperm concentration of 80 × 106 sperm cells/ml diluted semen. Diluted semen was packed in straws (0.25 ml) and stored in liquid nitrogen (−196 ◦C) for one month. After thawing, semen of each treatment was evaluated for sperm quality parameters, including sperm progressive motility, livability, morphological abnormalities, plasma membrane integrity and chromatin integrity. Apoptosis and sperm ultrastructure were also examined. Total antioxidant capacity and lipid peroxidation markers were determined in seminal plasma of semen in each treatment. Finally, the effect of Se-NPs on fertilization capacity was checked in vivo using n=81cows. The obtained results can be summarized as follows: First Experiment: Selenium nano-particles:-•The supplementation of Se-NPs at levels of 0.5 and 1.0 µg/ml to semen extender had a positive effect on sperm progressive motility, livability and membrane integrity as compared to the control. •Adding Se-NP at a level of 1.0 µg/ml improved percentage of viable sperm, while decreased percentages of early apoptotic, apoptotic and necrotic sperm cells as compared to the control. •Total antioxidants capacity (TAC) in seminal plasma increased and malondialdhyde (MDA) concentration decreased in semen supplemented with Se-NPs up to 1.0 µg/ml. •Addition of Se-NPs with concentration of 1.5µg/ml had negative effect on all parameters studied. •Treated bull semen extender with Se-NPs at a level of 1 µg/ml improved in vivo fertility rate (90%) compared with control (59%). Second Experimental: A. harveyi Leaf extract:-•The leaf extract ameliorated the damaging effects of the frozen-thawing process in cryopreserved bull semen. In a dose dependent pattern, sperm motility, viability, and membrane integrity were improved compared to the untreated control. •Furthermore, the extract increased the percentage of viable sperm and decreased the percentages of early apoptotic and apoptotic sperm cells as well as the damage in sperm ultra-structure. •These activities are in agreement with the robust antioxidant properties in vitro and in the seminal fluid as observed in the total antioxidant capacity and the lipid peroxidation parameter malondialdehyde. Conclusion:In conclusion, an overall improvement in progressive motility, livability, chromatin damage, sperm ultrastructure and in vivo fertility rate was observed when bull semen was extended with TEY supplemented with 1 μg/ml of Se-NPs in during cryopreservation which appears to have positive impact on antioxidant activity. Also, the A. harveyi leaf extract is rich in flavonoids namely myricetin, quercetin and kaempferol glycosides and polyphenol’s . The extract exhibited strong antioxidant activities in DPPH and FRAP assays ,as well as, in cryopreserved bull semen against the deleterious effects of freezing - thawing process when semen was supplemented with 1.5 μg/ml of Albizia harveyi leaf extract in the tris egg yolk fructose extender.