Luteotropic effects of human chorionic gonadotropin administered 7.5 days after synchronous estrous induction in Morada Nova ewes

Luteal tissue characteristics of Morada Nova ewes with hCG application 7.5 days after the end of estrus synchronization protocol in the breeding season

Results with the use of hCG after synchronization protocol are still inconsistent, which may vary according to breed, season, day of application and dose of the drug used. The aim of the present study was to evaluate the functionality of luteal tissue and ovarian perfusion after hCG treatment during early luteal phase. Estrus-synchronized ewes were randomly assigned to receive i.m. injection of 300 IU of hCG (G-hCG; n = 40) or 1 mL of saline (G-Control; n = 32) on Day 7.5 after progesterone withdrawal. Ultrasonographic evaluations of the ovaries and ovarian and iliac arteries were performed on Days 7.5, 10.5, 13.5, and 21.5. The accessory corpus luteum (aCL) formation rate was 52.5% for G-hCG. There was interaction (p > 0.05) for treatment (G-hCG and G-Control), days (7.5, 10.5, 13.5 and 21.5) and PD (Pregnant and Non-pregnant) for the variables of biometric characteristics of the corpus luteum B-Mode and Color Doppler on days 7.5, 10.5, 13.5 and 21.5. There was no difference (p > 0.05) for pregnancy rates and mean fetuses per ewe between the treatment groups. It is concluded that the application of hCG 7.5 days after the hormonal protocol in Morada Nova ewes in a breeding season is efficient in inducing aCL formation and increasing luteal tissue biometry. However, there was no effect on pregnancy rate.

Luteal function in cyclic goats treated with human chorionic gonadotropin administered by intramuscular or intravaginal routes at the time of artificial insemination

Human chorionic gonadotropin (hCG) has been used to improve goats reproductive efficiency. This study aimed to (i) evaluate if hCG administered by the intramuscular (i.m.) or intravaginal (i.vag.) route can be detected by a rapid β-hCG test in blood plasma samples and (ii) document ovarian effects of hCG administered by both routes at the time of artificial insemination (AI) performed 60 h after oestrus synchronization in goats. Twenty-two Alpine goats received two i.m. injections of 30 μg of d-cloprostenol (Prolise®, Tecnopec, São Paulo, Brazil) 7.5 days apart. One day after the onset of oestrus (at the time of AI), the goats were randomly allocated to one of the three groups that received: control (n = 7): 0.3 ml of saline solution intravaginally; hCGi.m. (n = 7): 300 IU of hCG (Vetecor®; Hertape-Calier, São Paulo, Brazil) i.m. and hCGi.vag. (n = 8): 300 IU of hCG deposited intravaginally. Blood samples were drawn at -1, 3, 6, 9 and 24 h after as well as on days 3, 7, 10, 13, 17 and 21 after hCG treatment/AI. All animals tested negative for hCG (ECO Diagnóstica, Corinto, Brazil) at -1 h, and all control animals tested negative throughout the entire blood collection period. All hCGi.m. animals tested positive from 3 h until D3 post-AI but only 50% of hCGi.vag. goats tested positive during the present study. In all animals studied, mean circulating P4 concentrations increased (p < .05) from D3 to D7 after AI and then declined (p < .05) from D10 to D17 in control and hCGi.m. groups and from D17 to D21 in the hCGi.vag. group. Total cross-sectional luteal area (CLA), mean colour Doppler area (DA), DA/CLA, mean high-velocity Doppler area and HVDA/CLA all declined (p < .05) by D17-D21 in all animals studied. In summary: (i) human chorionic gonadotropin could consistently be detected in blood samples using the rapid β-hCG test only in the hCGi.m. group; and (ii) there were no significant differences in the mean pregnancy rate, circulating P4 concentrations and various luteal parameters studied among Control, hCGi.m. and hCGi.vag. dose.

Hormonal-Induced Cervical Relaxation During Diestrus in Ewes: Cervical Transposing Feasibility and Use of hCG for Rescuing Disrupted Luteal Function

Cervical relaxation (CR) was performed in ewes during diestrus, to prospect a feasible protocol for non-surgical embryo transfer (NSET). In Trial 1, naturally mated ewes (n=13) received CR protocols with estradiol benzoate (EB, 1 mg on D6) and oxytocin (OT, 50 IU on D7) only (G-EB+OT) or associated with human chorionic gonadotropin (hCG, 300 IU on D7, G-EB+OT+hCG) and were compared to non-hormonally treated (G-control) ewes. Estradiol concentration increased (P<0.05) from D6 to D7 in G-EB+OT and G-EB+OT+hCG, then decreased (P<0.05) on D8. The G-EB+OT had reduced (P<0.05) progesterone on D8, and 0% (0/5) pregnancy, while G-control had 100% (3/3) conception rate. The treatment with hCG mitigated the progesterone drop on D8 and resulted in 50% (2/4) conception rate. In Trial 2, cervical transposing success after treatment with EB, OT, and hCG on D6 and D7 was assessed in nulliparous (n=25) and multiparous (n=30) ewes. The EB+OT+hCG protocol allowed efficient cervical transposition (~78% of cervical transposition success into ~5 min) in nulliparous and multiparous females and did not alter total and blood perfusion areas of corpora lutea (CL). The use of EB+OT+hCG was efficient to ensure effective cervical transposing in nulliparous and multiparous ewes, with no apparent deleterious effect on CL function, and may contribute to animal welfare, allowing a less invasive NSET procedure.

Effect of hCG administration on Day 7 post-mating on accessory corpus luteum development and progesterone concentration in llamas

A high embryo loss rate has been reported in llamas. As strategies that lead to an increase in plasma progesterone (P4) concentration might improve fertility, the aim of the present study was to evaluate if the administration of hCG on Day 7 post-mating is useful to develop an accessory corpus luteum (CL), increasing plasma P4 concentration. Twenty (n = 20) female llamas, ranging between 5 and 10 years of age and four (n = 4) males of proven fertility, ranging between 8 and 10 years of age were included in the study. Accessory CL developed in all treated llamas after hCG administration and plasma P4 concentration was significantly greater in treated than in control females (P˂0.0001). The diameter and vascularization of the original CL were not affected by treatment in pregnant llamas. However, in treated non-pregnant llamas, corpus luteum diameter was greater than in the control group from Day 14 post-mating until the end of the study (P˂0.001). In treated llamas, the accessory CL was detected throughout the study in pregnant and non-pregnant females, but its vascularization started to decrease around Day 16 post-mating in non-pregnant animals (P˂0.05). In conclusion, hCG treatment on Day 7 post mating was useful to induce an accessory CL and increase plasma P4 concentration in llamas. Thus, this treatment could be considered as a useful strategy to improve pregnancy rates in llama herds.