Equine chorionic gonadotropin (eCG) treatment in heifers: Double ovulation, twinning rate, and pregnancy losses in twin pregnancies.

This study aimed to evaluate the effects of different doses of equine chorionic gonadotropin (eCG; 200 and 300 IU) administered at the end of a fixed-time artificial insemination (FTAI) treatment protocol on ovulation, pregnancy, and twin rates in Bos taurus beef heifers. In addition, pregnancy losses in heifers with singleton and twin pregnancies were determined. A total of 2382 Angus heifers treated with a 6-day estradiol/progesterone-based protocol for FTAI (J-Synch protocol) were randomly allocated to two experimental groups to receive 200 or 300 IU of eCG administered intramuscularly at the time of intravaginal progesterone device removal; FTAI was performed from 60 to 72 h after device removal. The pregnancy rate did not differ (P = 0.89) between the 200 and 300 IU eCG groups. The number of corpus luteum induced by both eCG doses was determined by ultrasonographic examination 14 days after insemination and those treated with 300 IU of eCG had a greater double ovulation rate (P < 0.05). In addition, 300 IU eCG treated heifers had a higher twinning rate on day 30 of gestation (P < 0.05) and parturition (P < 0.05). Pregnancy losses from 30 days of gestation to calving did not differ between heifers treated with 200 and 300 IU of eCG (P = 0.70). However, regardless of the experimental group, heifers bearing twins had greater pregnancy losses than heifers with singletons (P < 0.05). In conclusion, reducing the dose of eCG from 300 to 200 IU under FTAI treatment protocol decreases double ovulation and twinning rates, maintaining a similar pregnancy rate in heifers. Nulliparous cows carrying two fetuses suffer greater pregnancy losses than cows with singletons.

Time of ovulation and pregnancy outcomes obtained with the prostaglandin-based protocol Synchrovine for FTAI in sheep.

The objective of the present study was to determine the ovarian response induced with the prostaglandin-based protocol Synchrovine (two doses of PGF2α given 7 d apart), as well as the fertility after FTAI. In Experiment 1, 15 females received the Synchrovine protocol using two different PGF2α analogues (Delprostenate vs. D-Cloprostenol). No differences in estrus response, time of ovulation and follicular dynamics were found between both groups (P < 0.05). The ovulation after Synchrovine was synchronized in a similar mean interval (68.8 ± 7.1 h) than when the females received a single dose of PGF2α (70.2 ± 20.7 h; P=NS), but the dispersion between the first and the last ovulation was reduced with this protocol (range 60-84 h vs. 24-96 h, respectively; P < 0.05). In experiment 2, 318 ewes were treated with the Synchrovine protocol and cervical FTAI was performed using different sperm cell concentrations. Pregnancy rate was higher using 200 × 106 and 100 × 106 sperm cells (38.2%, 39/102; and 34.9%, 38/109, respectively) than using 50 × 106 (23.4%, 25/107, P < 0.05). In Experiment 3, 444 ewes received the Synchrovine protocol and were assigned to receive 300 IU of eCG or not at the moment of the second dose of PGF2α, and cervical FTAI was performed 42 h or 48 h after the second dose of PGF2α. No effect was found related to the eCG administration nor the time of insemination. In Experiment 4, 342 received cervical or intrauterine insemination after treatment with the Synchrovine protocol, resulting in greater pregnancy rate for intrauterine insemination than cervical insemination (52.5%, 90/171 vs. 31%, 53/171, P < 0.05). These experiments demonstrate that the Synchrovine protocol effectively induces luteolysis, estrus and ovulation in most of the treated females, and ovulation is synchronized into a narrow window of 24 h. Pregnancy rate obtained with cervical FTAI is around 30-45%, with similar results using 100 × 106 or 200 × 106 sperm cells, the eCG administration seems not to be necessary, the type of PGF2α analogue does not appear relevant, and fertility is improved with intrauterine semen deposition.

Ovulatory response and luteal function after eCG administration at the end of a progesterone and estradiol' based treatment in postpartum anestrous beef cattle.

The objective of this study was to evaluate the effect of equine chorionic gonadotropin (eCG) administration associated to fixed-time AI (FTAI) on follicular dynamics, ovulation, corpus luteum (CL) development and serum progesterone concentrations. Multiparous suckled Hereford cows (n=46) in anestrus with 60-75 days postpartum were used. Females received an intravaginal device containing 0.5g of progesterone during 8 days and 2mg of estradiol benzoate i.m. at device insertion. At device removal 500µg of cloprostenol and 0.5mg of estradiol cypionate were administered i.m., and FTAI was performed 52-56h later. Cows were divided into two experimental groups to receive 400IU of eCG i.m. at device removal (n=23), while control group did not receive eCG (n=23). Daily ovarian ultrasonography (7.5MHz transducer) and progesterone concentrations determined by RIA were assayed from device removal until 30 or 14 days after FTAI, respectively. Treatment with eCG increased ovulation rate [65.2% (15/23) vs. 30.4% (7/23); P=0.018], ovulatory follicle diameter (14.5±0.4 vs. 13.1±0.7mm, mean±SEM; P=0.081), CL area from 6 to 14 days after FTAI (344.3±25.1 vs. 274.2±23.9mm(2); P=0.045) and mean serum progesterone concentrations from FTAI to 14 days later (3.0±0.2 vs. 1.8±0.2ng/ml; P=0.001), in comparison with control cows. In conclusion, the addition of eCG to a progesterone and estradiol' based treatment for FTAI improves ovulation rate and luteal function in anestrous cows. These findings have implications in order to increase pregnancy rates in FTAI treatments in Bos taurus beef cattle.