الفهرس 
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Abstract
To evaluate the monthly, seasonal and breed variations in physical and chemical semen characteristics of 10 Zaraibi, 10 Damascus and 10 Alpin bucks (1st Ex.). Also, semen of Zaraibi bucks was diluted with Tris extender containing different levels of egg yolk (2.5, 5.0 and 7.5%) to study the best level of egg yolk. Then, Tris containing non-centrifuged 2.5% egg yolk was compare with the same level of centrifuged extender and Tris extender containing 5.00 mM from butylated hydroxytoluene (BHT) instead of egg yolk (2nd Ex.).
Finally, semen collected from all breeds during all months of the year was frozen with Tris extender containg non-centrifuged 2.5% egg yolk versus 5.00 mM BHT (3rd Ex.), and conception rate (CR) from frozen semen collected during breeding and non-breeding season and extended with egg yolk or BHT was evaluated in breeding season for all breeds (the 4th exp.). The obtained results revealed that:
1- Zaraibi bucks showed the best semen quality, followed by Alpin, while Damascus bucks showed the poorest semen quality during most months of the year. 2- All goat breeds showed the best semen quality during autumn, followed by summer and winter, while the poorest semen quality in spring, although Zaraibi bucks tended to show non-seasonality in semen quality during different months of the year.
3- Level of 2.5% or 5.00 mM BHT had beneficial effects on sperm motility during different freezing processing stages, being the best with Zaraibi semen. Also, adding 5.00 mM from BHT as cryoprotectants instead of 2.5% egg yolk resulted in the best sperm motility during different freezing processing stages.
4- Autumn (especially in October month) showed the best season for freezing semen extended in Tris BHT extender from all goat breed studied.
5- CR of does markedly improved when semen was collected during non-breeding season and extended with Tris-BHT.