الفهرس 
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Abstract
This study aimed to : This study was conducted at El-Karada Animal Production Research Station and International Livestock Management Training Center, (ILMTC)-Sakha, Kafrelshiekh governorate, belonging to Animal Production Research Institute (APRI), Agricultural Research Center (ARC), Ministry of Agriculture in co-operation with Animal Production Department, Faculty of Agriculture, Mansoura University during the period from January to October 2013 to determine the effect of different synchronization regimens as exogenous progesterone on ; (1) ovarian follicular dynamics and superovulatory response, (2) hormonal profile (P4) during superovulation treatment, (3) embryo production, quality and cryopreservation in Friesian cows. Cows were divided into 3 experimental groups (8 animals in each). Cows in G1 were injected intramuscularly (i.m) with 3 ml PGF2α/cow to bring them on heat (start of estrous cycles). Cows were i.m. injected with 3000 IU of PMSG/cow on day 10 of the estrous cycle, and 48 hours later with 3 ml PGF2α/cow. Cows received this protocol were considered as control group. Cows in (G2) were received Synchro-Mate-B ear implant and i.m. injected with 5 mg estradiol benzoate (EB) and 100 mg of progesterone/cow on day of implantation. Seven days later, all cows were i.m. injected with 3000 IU of PMSG and 3 ml of PGF2α/cow. Two days later implants were removed. This protocol was initiated without any information about the previous estrous cycle. Cows in (G3) were received controlled internal drug release (CIDR) intravaginal and i.m. injected with 4 mg EB. CIDR were removed 7 days later, and cows were i.m. injection of 3000 IU of PMSG and 3 ml of PGF2α on day of CIDR withdrawal. Also, this protocol was initiated without any information about the previous estrous cycle. All cows artificially inseminated (AI) when excepted estrous. Flushing was conducted 7 days after AI. Collected embryos were evaluated morphologically and were classified into different grades. Measurements of embryos were recorded. Embryos cryopreserved with closed pulled straw. Blood samples were collected and Ultrasonography examination at treatment days in all experimental groups. The obtained results could be summarized as the following :
•Number and diameter of follicles and diameter of largest follicles were affected significantly (P<0.05) by treatment only at post‒PGF2α (G1), SMB (G2) and CIDR (G3) treatment. Number of CLs was affected significantly (P<0.001) by treatment at day 0 and on day post‒treatment.
•On day of flushing, average number of CLs/cow was affected significantly (P<0.05) by superovulation protocol, being greater in G3 than in G1 and G2. Such results were reflected in significantly (P<0.05) higher ovulation rate in G3 than in G1 and G2.
•Results revealed that number of embryos/cow was the greatest in cows of G3, moderate in G1 and the lowest in G2.Progesterone (P4) concentration was affected significantly by superovulation treatment only during-treatment (P<0.001) and post-treatment (P<0.01).
•Results based on embryos at all stages revealed that embryos of cows in G2 showed the highest post-vitrfication survival and normality rates, flowed by G3 and G1. Conclusively, the present results indicated that using controlled internal drug release (CIDR) device as progesterone source and 4 mg estradiol benzoate (EB) at insersion with 3000 IU of pregnant mare serum gonadotropin (PMSG) in superovulation protocol of Friesian cows resulted in high ovulatory response in terms of ovulation rate, and number of transferable embryos of excellent and good grades. However, further studies are required for improving embryos survival and normality during cryopreservation.