期刊
JOURNAL OF ANIMAL SCIENCE
卷 91, 期 3, 页码 1176-1185出版社
AMER SOC ANIMAL SCIENCE
DOI: 10.2527/jas.2012-5611
关键词
beef cattle; embryo transfer; estradiol; estradiol cypionate; follicle diameter; pregnancy
资金
- National Research Initiative Competitive Grant from the USDA National Institute of Food and Agriculture [2006-35203-17284]
- Pfizer
- TEVA Animal Health
In postpartum beef cows, GnRH-induced ovulation of small dominant follicles decreased pregnancy rates and increased late embryonic/fetal mortality. In Exp. 1, single ovulation reciprocal embryo transfer (ET) was used to examine the relationship between preovulatory serum concentrations of estradiol at GnRH-induced ovulation in donor and recipient cows and establishment and maintenance of pregnancy. Suckled beef cows (n = 1,164) were administered GnRH (GnRH1, 100 mu g) on d -9 (GnRH1), PGF(2 alpha) on d -2, and GnRH2 (GnRH2, 100 mu g) on d 0 (CO-Synch protocol) either with (donors; n = 810) or without (recipients; n = 354) AI. Single embryos (n = 394) or oocytes (n = 45) were recovered from the donor cows (d 7; ET) and all live embryos were transferred into recipients. Serum concentration of estradiol at GnRH2 was positively correlated with follicle size at GnRH2 (r = 0.45, P < 0.01) and progesterone at ET (r = 0.34, P < 0.01). Donor cows with greater estradiol at GnRH2 were more likely to yield an embryo than an unfertilized oocyte (P < 0.01). Donor and recipient cows were retrospectively divided into 4 groups [low estradiol (<8.4 pg/mL) or high estradiol (>= 8.4 pg/mL)] based on serum concentration of estradiol at GnRH2. Pregnancy rate at d 27 for low-low (n = 78), low-high (n = 80), high-low (n = 91), and high-high (n = 101) groups (donor-recipient, respectively) was 45, 65, 43, and 61% respectively (P < 0.02). Because recipient cows with greater estradiol concentration at GnRH2 had greater pregnancy rates in Exp. 1, the objective of Exp. 2 was to evaluate the effect of estradiol supplementation on pregnancy rate. Ovulation was synchronized in suckled beef cows (n = 600) using the CO-Synch protocol with the insertion of a controlled internal drug release (CIDR; intravaginal progesterone supplement) from d -9 until d -2. Approximately one-half of the cows (n = 297) received an injection of estradiol cypionate (ECP; 0.5 mg intramuscularly) 24 h before AI. Compared with the no treatment (Control) cows, ECP treatment increased (P < 0.01) pregnancy rates of cows induced to ovulate smaller dominant follicles (<12.2 mm). In conclusion, GnRH-induced ovulation of small dominant follicles was associated with reduced serum estradiol, fertilization rate (donor cows), and pregnancy establishment (recipient cows). Furthermore, ECP supplementation during the preovulatory period increased pregnancy rates in cows induced to ovulate smaller dominant follicles. (C) 2013 American Society of Animal Science. All rights reserved.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据