الفهرس 
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Abstract
The current work was conducted in El-Zahra Governmental Stud, belonging to the Egyptian Agriculture Organization (E.A.0). Sixteen matyre healthy Arabian stallions were selected for this study. The age of stallions ranged from 4-19 years at the beginning of this work (from December, 1992 to November, 1993 ). To study the effect of age animals categorized into 4 age groups each including 4 stallions.
Group I : 4 - 7 years
Group II : 8 - 11 years
Group III : 12 - 15 years
Group IV : 16 - 19 years
I-Semen characteristics :
To study the effect of seasons on semen characteristics one ejaculate was collected once monthly from each stallion throughout a period of one year, data were grouped by seasons according to the conventional classification as follows :
1-winter (December - February )
2-Spring (March - May )
3-Summer( June - August )
4-Autumn (September-November)
Semen collection :
semen was collected from stallions using an artificial vagina. The gelatinous material (gel) at the end of ejaculate was separated. Evaluation of gel- free semen was
performed.
Major sperm abnormalities :
Amarked increase in the % of defective spermatazoa was recorded during November. (18.56%). The lower level was observed during October (7.51 %).
-Seasons had no any significcance on the percentage of major abnorpmalities.
-Semen obtained from young stallion GI contain the highest % of defective sperm.
(15.04%) which decline significantly with advancement of age to reach 10.52% in GIII.
Minor sperm abnormalities :
- The difference between months were non-significant. - The effect of season was non-significant.
- Semen obtained from young stallions GI had significant higher % than older stallions of Gil , III and IV.
- Proximal protoplasmic droplets :
-Monthly differences were statistically non. significant.
-The effect of season was non-significant.
-The percentage of spermatozoa with proximal dropletes was significant higher in G IV than in other 3 age groups.