الفهرس 
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Abstract
This study was carried out at Animal Production Research Station, co-operation with Animal Production Research Institute, Faculty of Agriculture Kafrelsheikh University.
This study included two main study; the first study was a survey study and the secondary study included hormonal protocol which divided into four groups as the following:
Repeat breeder cows in group 1 (G1) was treated with GnRH on day of artificial insemination (AI). (G2) was treated with hCG on day of insemination . (G3) GnRH on 0 day followed by 7 days later by injection PGF2α, GnRH on days 9 and 16-20 h later AI. (G4) (hCG) (day 0) followed 7 days PGF2α followed 2 days hCG , followed 16-20 h later with timed artificial insemination.
The obtained results could be summarized as the following:
1. Survey study:
Calving interval , Days open, Pregnancy period ,First services interval of calving, Number of service per conception, Service period ,Average daily milk yield : Overall means in normal cows and repeat breeder cows were significantly higher in repeat breeder cows than in normal cows in all different parities.
2. Diagnostic study:
Repeat breeder cows treated with hCG+PGF2α-hCG timed AI protocol improve their reproductive performance. from the economic point of view showed the best results (pregnancy rate and moderate costs) compared to the other protocols.