Although it induces synchronized ovulation, hCG reduces the fertility of Santa Ines ewes submitted to TAI

A Subovulatory Dose of Human Chorionic Gonadotropin (hCG) May Sustain Terminal Follicle Development and Reproductive Efficiency during Anestrus in Sheep

The study tested the hypothesis that a single administration of hCG supports the LH-dependent phase of terminal follicular development in synchronized sheep during anestrus, using eCG as a functional reference. Using a clinical approach, four experiments were designed to achieve the following: (1) Identify the inhibitory influence of anestrus on reproduction efficiency; (2) Assess the potential of hCG to keep functional blood concentrations after a single dose; (3) Characterize the effect of different doses of hCG on reproductive functional markers; (4) To compare the ability of hCG to that of eCG to support follicular development and fertility based on the same markers. The results showed that anestrus seems to affect follicular and luteal function under LH dependency as FSH-dependent markers are not compromised; hCG maintains higher blood concentrations than controls for at least 48 h; hCG improves follicular development and ovulatory rates compared to controls and at standards comparable to a breeding season; and ewes treated with hCG exhibit similar performance to those treated with eCG. Our results conclude that hCG can be used to support follicular function during anestrus in sheep, aiming to perfect its regulation in assisted reproduction.

The effect of progesterone injection combined with prostaglandineF2α, GnRH and hCG administrations on the pregnancy and lambing rate of lactating and non-lactating fat-tailed ewes during the breeding season

The objective was to compare the effect of human chorionic gonadotropin (hCG) and gonadotropin-releasing hormone (GnRH) on the pregnancy and lambing rate of treated ewes with a short-term progesterone (P4) injection during the breeding season. In Exp 1, non-lactating ewes (n = 158) were used and received P₄ , three times every 48 h and received PGF_2α along with the last dose of P4. Ewe received hCG (n = 79, 3PHCG, IM) or GnRH (n = 79, 3PGnRH, IM) 24 h after the last dose of P4 treatment. In the Exp 2, lactating ewes (n = 62) received P4 and hCG (n = 24, 3PHCG) or GnRH (n = 24, 3PGnRH) similar to Exp 1, or considered as control (n = 14) and received PGF2α 48 h before ram release. Rams were released into the studied ewe's flock 24 h after the hCG or GnRH administration, and pregnancy diagnosis was performed on day 50 after ram release. In Exp 1, all reproductive indices were not significant between groups except twin lambing rate, that was higher in the 3PHCG (11.3%) compared with the 3PGnRH (1.9%) group (p = .05). There were no significant differences in overall pregnancy and lambing rates between 3PHCG (70.9% and 67.1%) and 3PGnRH (69.6% and 68.4%) groups (p > .05). In Exp 2, all reproductive parameters were not significant between 3PHCG and 3PGnRH groups (p > .05). There was significant difference in overall oestrous rate between control (35.7%) and treatment (3PHCG, 70.9% and 3PGnRH, 79.2%) groups. To conclude, administration of GnRH can be a good alternative to hCG injection under field conditions.

Efficiency of hCG for Inducing Resumption of Ovarian Cyclicity and Synchronized Ovulations during the Seasonal Anestrous in Sheep

Simple Summary

The use of equine chorionic gonadotrophin (eCG) in protocols for estrus synchronization in sheep is currently challenged, so it is necessary to implement alternatives (i.e., human chorionic gonadotropin; hCG), mainly during the anestrous season. Therefore, we compared the reproductive outcomes, including estrus induction, ovulatory follicle dynamics, and pregnancy outputs in anestrus Dorper sheep treated with insertion of one intravaginal progesterone-loaded CIDR + either saline, eCG, or hCG. The administration of hCG at the time of CIDR removal was effective at inducing estrus, resume ovulations, and ovarian cyclicity, yet, in a narrow window of time, it is a scenario that may limit the implementation of an artificial insemination protocol.

Abstract

This research aimed to evaluate whether the administration of hCG at the time of removal of a progesterone device may be effective at inducing estrus and ovulations in sheep during the natural seasonal anestrous, by comparing reproductive outputs (induction and duration of estrus, follicle development, ovulation, ovulation rate, and pregnancy rates) in ewes treated with eCG or only saline solution at the time of CIDR removal. Whereas results demonstrated no response in the control non-treated group, the largest rate of narrowly synchronized estrus signs and ovulations occurred in the eCG-group. The administration of hCG was effective at inducing estrus, promote follicular growth and a delayed yet significant ovulation (>84%) on day 10 after CIDR removal; moreover, an increased embryonic implantation rate was also observed. Moreover, if the hCG ewes remain exposed to active males for some days, said strategy could be adopted, aiming to induce pregnancies by natural mating in a short period of time.

The Use of hCG for Inducing Ovulation in Sheep Estrus Synchronization Impairs Ovulatory Follicle Growth and Fertility

Simple Summary

The present study, in view of the importance of finding an alternative hormone to eCG, aims to determine the response of sheep to hCG-based treatments. The findings indicate that the low fertility rates reported for protocols based on the administration of hCG for inducing ovulation during estrus synchronization in sheep may be related to a high occurrence of abnormal follicular growth patterns, disturbances, and retardments of ovulation and concomitant formation of follicular cysts in the treated females. These results preclude their practical application to induce ovulation concomitantly to estrous synchronization treatments.

Abstract

Currently, there is an intense effort to find an alternative hormone to eCG to induce ovulation after estrus synchronization treatments in sheep. One of the proposed alternatives is based on the use of hCG, but the results are controversial since fertility rates are commonly affected. The present study aims to evaluate, therefore, the adequacy of hCG in protocols for the synchronization of estrus and ovulation. Ovarian follicle dynamics, occurrence of estrus behavior and subsequent ovulation, quality of corpora lutea, and pregnancy rate after controlled natural mating were assessed in two consecutive trials. The findings indicate that the low fertility rates reported for the protocols based on the administration of hCG for inducing ovulation during estrus synchronization in sheep may be related to a high occurrence of abnormal follicular growth patterns, disturbances, and retardments of ovulation and concomitant formation of follicular cysts in the treated females. These results preclude their practical application to induce ovulation concomitantly to estrous synchronization treatments.

Effect of different protocols for estrus synchronization on reproductive performance of Santa Inês ewes under Amazon environmental conditions

 The objective of this study was to evaluate the effect of different hormonal protocols on the reproductive performance of Santa Inês ewes in Amazon environmental conditions. Twenty-two Santa Inês ewes between 3 and 4 years-old were distributed in a randomized block experimental design, where the treatments consisted of two protocols for estrus synchronization (short and long) with eleven animals each. Data on the occurrence of estrus were described for each protocol. Data of estrus, pregnancy, and prolificity were firstly subjected to ANOVA and a subsequent Tukey’s test. Results were considered significant at p ≤ 0.05. The short-term protocol presented an interesting successful rate, where above 70% ewes tested had estrus. The long-term protocol also achieved a high successful rate, where above 80% ewes tested had estrus. However, comparing the protocols, the long-term protocol presented better results of positive estrus and pregnancy rates in ewes. Thus, it can be concluded that both protocols presented satisfactory results regarding estrus manifestation, and prolificity (lambs produced per ewe). However, under Amazon environmental conditions, the long-term protocol presented better results regarding positive manifestation of estrus and pregnancy rate.