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Ahmed Elmetwally MohammedCorresponding author Department of Theriogenology, Veterinary Medicine Faculty, Mansoura University, Mansoura 35516, Egypt
Following parturition in the cow, there is a significant period of sexual quiescence of variable length. This period of reproductive quiescence was found to be longer in suckling or intensively milked animals.This acyclic period is generally considered as the postpartum anoestrous period. The postpartum period constitutes an important period in the reproductive life of dairy cows because of its enormous influence upon subsequent fertility. The entire postpartum period, puerperium, is defined as the period from parturition until the genital organs return to its normal physiological and histological condition, as in normal non-gravid state. They added that any extension of the puerperium in cows might have a detrimental effect on the reproductive performance of the individual animal. Thus, the main determinant of this period is essentially dependent on the resumption of normal ovarian cycles, the manifestation of estrus behaviour and conception following insemination.
A Elmetwally MohammedCorresponding author Departments of Theriogenology,
This review focused on the various methods for controlling estrous cycles in well-managed dairy cows. Because up to 70% of dairy cows may stay non-pregnant after an AI procedure, an effective approach for identifying and reinseminating open cows is essential for dairy herds to achieve optimal reproductive performance. Overall, well-managed dairy farms with effective estrus detection programs inseminate 50% or more of non-pregnant cows after behavioral estrus is detected. Cows not detected in estrus are admitted in a resynchronization of ovulation procedure to receive a timed AI (TAI) service to avoid a long interbreeding interval. In Egypt, a widely used program involves starting the Ovsynch protocol (GnRH-7 d-PGF2-56 h-GnRH-16 to 20 h-TAI) 32 days after an initial AI, regardless of pregnancy status. Previous studies have proven that there was no difference in pregnancy/artificial insemination (P/AI) between Ovsynch+P4 and Presynch-Ovsynch, both protocols were equally effective in improving the fertility of cows with a CL 15 mm. The review also addressed different methods for synchronization of ovulation and different factors affecting the selection of the management program.