The Effect of Administering Equine Chorionic Gonadotropins (eCG) on Reproductive Performance of Dairy Cows with a CO-Synch + CIDR Protocol and Insemination at a Fixed Time
محورهای موضوعی : Camel
م.م. منشادی
1
(Department of Clinical Science, Faculty of Veterinary Medicine, Urmia Branch, Islamic Azad University, Urmia, Iran)
ع. رستگارنیا
2
(Department of Clinical Science, Faculty of Veterinary Medicine, Urmia Branch, Islamic Azad University, Urmia, Iran)
Sh. اسماعیلی ثانی
3
(Department of Clinical Science, Faculty of Veterinary Medicine, Urmia Branch, Islamic Azad University, Urmia, Iran)
کلید واژه: dairy cows, estrus synchronization, CIDR, equine chorionic gonadotropin,
چکیده مقاله :
The success of a fixed-time artificial insemination (FTAI) program depends on a high ovulation rate during a short interval. Equine chorionic gonadotropin (eCG) has been used in FTAI protocols to improve follicular growth and thereby to produce larger, more responsive follicles for ovulation with increased pregnancy rates. The aim of the present study was to evaluate the effects of eCG on conception rates of early post-partum dairy cows treated by progesterone-based estrous synchronization with artificial insemination at a fixed time (CO-Synch+CIDR protocols). 144 Holstein cows ≥ 55 days postpartum were used. All cows were enrolled in a 7-day CO-Synch + CIDR protocol which included 100 μg gonadotropin releasing hormone (GnRH) at CIDR insertion (day 0); 500 µg prostaglandin F2α (PGF2α) at CIDR removal (day 7); and 100 μg GnRH at FTAI, 66 hours after PGF2α (day 10). Cows were randomly assigned as control cows (n=69) or treated cows (n=75) which received 500 IU eCG at the time of CIDR removal. All cows were examined by ovarian ultrasound at FTAI. The addition of eCG to CO-Synch+CIDR protocols improved the frequency of estrous response (control cows 51.4%, eCG-treated cows 87.8%; P<0.01). It reduced the interval between the end of treatment and the start of estrus (control cows 56.8±5.52 hours, eCG-treated cows 45.7±5.87 hours; P<0.01). It increased dominant follicular size at FTAI (control cows 15.1±2.41 mm, eCG-treated cows 19.6±1.84 mm; P<0.001). However, eCG had no effect on pregnancy rates (control cows 49.3%, eCG-treated cows 54.6%; P=0.131). The use of eCG, prior to termination of 7-day estrus synchronization when using the CO-Synch+CIDR program alone, could hasten the time of estrous expression and should be considered in FTAI dairy cows.
موفقیت در برنامه تلقیح مصنوعی در زمان ثابت بستگی به میزان بالای تخمک­گذاری در فاصله زمانی کوتاه مدت درمان دارد. استفاده از هورومون eCG در انتهای برنامه همزمان­سازی فحلی با افزایش میزان رشد فولیکولی منجر به تولید فولیکول بزرگ و حساس به تخمک­گذاری و افزایش میزان آبستنی در دام می­گردد. هدف از این تحقیق تأثیر تزریق eCG در انتهای برنامه همزمان­سازی فحلی و تلقیح در زمان ثابت با استفاده از سیدر (CO-Synch+CIDR) بر روی میزان آبستنی گاو­های شیری بود. تعداد 144 رأس گاو شیری با فاصله زمانی 55≥ انتخاب و در زمان شروع آزمایش سیدر داخل واژنی به همراه 100 میکروگرم GnRH دریافت نمودند. در روز هفتم آزمایش، تمامی دام­ها 500 میکروگرم PGF2α دریافت داشته و به دو گروه کنترل و درمان تقسیم گردید. دام­های گروه درمان 500 واحد بین المللی هورمون eCG نیز دریافت نمودند. سیدر در روز هفتم آزمایش خارج گردید. تلقیح مصنوعی تمامی دام­ها حدود 66 ساعت پس از خروج سیدر انجام گردید. سونوگرافی تخمدان­ها همزمان با تلقیح تمامی دام­ها به منظور بررسی اندازه فولیکول غالب صورت گرفت. افزودن eCG در انتهای برنامه (co-synch) باعث افزایش میزان فراوانی میزان بروز فحلی (گروه درمان: 8/87 درصد، گروه کنترل: 4/51 درصد) گردید (01/0P<). فاصله خاتمه درمان تا آغاز علائم فحلی در گروه کنترل (52/5±7/56 ساعت) طولانی­تر از درمان (87/5±7/45 ساعت) بود (001/0P<). اندازه فولیکول غالب (41/2±1/15 میلی­متر) در گروه کنترل بیشتر از درمان (84/1±4/19 میلی­متر) بود. از سوی دیگر تزریق eCG تأثیری بر میزان آبستنی (گروه درمان: 4/54 درصد، گروه کنترل: 3/49 درصد) نداشت (131/0P=). به طور کلیاستقاده از هوزمون eCG، در انتهای برنامه 7 روزه در در برنامۀ (co-synch+CIDR) می­تواند سبب جلو انداختن زمان بروز فحلی گردد که باید در برنامه تلقیح در زمان ثابت گاو­های شیری مورد توجه قرار گیرد.
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