الفهرس 
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Abstract
The present study was conducted in the Animal Production Department, Faculty of Agriculture, Menufia University in corporation with Animal Production Research Institute (APRI), Agricultural Research Center, Egypt. The study was mainly conducted to:
1- Studying the major changes in β -endorphin and cortisol levels the in blood plasma of Egyptian buffaloes and Friesian cattle during the following periods: The trimester of pregnancy; periparturient as well as the post-partum period which included the different phases of the estrous cycle and lactation.
2- Studying the impact of some reproductive disorders that may occur during these periods as: dystocia, retained placenta and productive disorders like low body condition score on the activity of these hormones (β-EP and cortisol).
The experimental work was preceded by a preliminary observation of all pregnant buffalo and Friesian cows of the herd under consideration during the last trimester of pregnancy (precisely, two months before parturition until 4 months after parturition).
The experimental buffaloes and Friesian cattle were fed a balanced meeting ration got their feed allowances according to their LBW and BCS as recommended by (APRI, 1997), plus water free choice, healthy and kept under similar managerial conditions. Through the last ten days of pregnancy, the mother’s birth canal for each experimental animal was examined and monitored by rectal palpation. By week before parturition process, a body condition score (BCS) was recorded for each dam. One day before delivery, the selected experimental animals were kept in the delivery units for observation until the time of calving. At calving, the type of parturition for each buffalo or Friesian cattle was closely observed and recorded.