الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Summer heat stress is the most contributing factor to low fertility of dairy cows inseminated in the summer months. This brought dairy farmers to develop and implement new technologies and management practices that would enable high reproduction and production in summer. One of the most important these technologies used in animal management practices is the Doppler ultrasound. It extended the scope of sonographic imaging from an anatomical to a physiological basis of CL and early conceptus. Also provides supplementary information about the degree of blood flow making the diagnosis more easily and therefore more accurate. Therefore, this study throws the light on:
6- The deleterious effects of heat stress during summer on fertility and reproductive parameters of the farm (service per conception, conception rate and late embryonic and early fetal losses).
7- Using Doppler ultrasoungraphy to investigate the effect of heat stress on the blood flow in the ipsilateral and controlateral uterine arteries during the early pregnancy by blood flow indices (TAMV, PI, RI and S/D ratio) and comparing between winter and summer.
8- Using Doppler ultrasound to investigate the effects of heat stress during summer on the luteal blood flow indices (CL area and CL colored area) and comparing it with winter.
9- The effect of heat stress on the progesterone secretion in winter and summer during the early gestation.
10- Investigate the correlation between effects of heat stress on the uterine and luteal blood flow on the fertility.
The present study was performed on 40 cyclic Holstein-Friesian cows (20 cows during winter and 20 cows during summer) during the early.