Effective embryo production from Holstein cows treated with gonadotropin-releasing hormone during early lactation

Mapping the follicle-specific regulation of extracellular vesicle-mediated microRNA transport in the southern white rhinoceros (Ceratotherium simum simum)†

Efforts to implement effective assisted reproductive technologies (ARTs) for the conservation of the northern white rhinoceros (NWR; Ceratotherium simum cottoni) to prevent its forthcoming extinction, could be supported by research conducted on the closely related southern white rhinoceros (SWR; Ceratotherium simum simum). Within the follicle, extracellular vesicles (EVs) play a fundamental role in the bidirectional communication facilitating the crucial transport of regulatory molecules such as microRNAs (miRNAs) that control follicular growth and oocyte development. This study aimed to elucidate the dynamics of EV-miRNAs in stage-dependent follicular fluid (FF) during SWR ovarian antral follicle development. Three distinct follicular stages were identified based on diameter: Growing (G; 11-17 mm), Dominant (D; 18-29 mm), and Pre-ovulatory (P; 30-34 mm). Isolated EVs from the aspirated FF of segmented follicle stages were used to identify EV-miRNAs previously known via subsequent annotation to all equine (Equus caballus; eca), bovine (Bos taurus; bta), and human (Homo sapiens; hsa) miRNAs. A total of 417 miRNAs were detected, with 231 being mutually expressed across all three stages, including eca-miR-148a and bta-miR-451 as the top highly expressed miRNAs. Distinct expression dynamics in miRNA abundance were observed across the three follicular stages, including 31 differentially expressed miRNAs that target various pathways related to follicular growth and development, with 13 miRNAs commonly appearing amidst two different comparisons. In conclusion, this pioneering study provides a comprehensive understanding of the stage-specific expression dynamics of FF EV-miRNAs in the SWR. These findings provide insights that may lead to novel approaches in enhancing ARTs to catalyze rhinoceros conservation efforts.

The effectiveness of different hormone protocols for improving ovarian function before ovum pick-up in crossbred Japanese black cattle

Background and Aim

Producing and transferring embryos in vitro are profitable for enhancing premium beef genetics. Reducing costs and enhancing the effectiveness of hormone protocols before ovum pick-up (OPU) yield advantages. This study aimed to confirm that estradiol benzoate (EB) treatment resulted in more medium- and large-sized follicles before OPU and of higher oocyte quality after OPU than non-hormonal treatments, comparable to those undergoing gonadotropin-releasing hormone (GnRH) with follicle-stimulating hormone (FSH) plus prostaglandin F2α (PGF2α) and progesterone-releasing controlled internal drug release (CIDR) or EB with progesterone-releasing CIDR hormonal treatments.

Materials and Methods

30 crossbred Japanese black cows were divided into five equal groups, which were either untreated or treated with different hormone protocols before OPU. Group 1 (cows in estrus) and group 2 (cows in diestrus) were the untreated controls. Cows in group 3 were treated with GnRH + FSH + CIDR + PGF2α. Cows in group 4 received EB, and those in group 5 received EB + CIDR + PGF2α. After administering the protocols, all cow follicles were examined through ultrasonography and categorized by size. Subsequently, all cows underwent OPU, and the oocytes were collected and graded from A to D according to standard criteria.

Results

Group 3 presented the highest large follicle numbers, and groups 3-5 had more medium follicle numbers, not different among groups but they had this parameter more than those of control groups 1 and 2. Moreover, groups 3-5 did not differ in combined grades A + B oocytes (good-quality oocytes). Groups 3 and 4 had more A + B oocytes than control groups 1 and 2, whereas group 5 was not different in this parameter from group 1.

Conclusion

Among the three hormone protocols, EB treatment proved the most cost-effective and efficient, yielding more high-quality oocytes compared to the non-treatment protocols. To reduce the limitations of EB use in the future, this study suggests researching natural EB phytoestrogens as alternative treatments for improving ovarian function before OPU in other cattle breeds.

Pregnancies following long luteal phases in southern white rhinoceros (Ceratotherium simum simum)

All extant species in the Rhinocerotidae family are experiencing escalating threats in the wild, making self‐sustaining captive populations essential genetic reservoirs for species survival. Assisted reproductive technologies (ARTs) will become increasingly important for achieving and maintaining ex situ population sustainability and genetic diversity. Previous reports have shown that a large proportion of captive southern white rhinoceros (SWR) females are irregularly cyclic or acyclic, and that cycling females display two different estrous cycle lengths of approximately 30 or 70 days. It has been suggested that the longer estrous cycle length is infertile or subfertile, as no term pregnancies have been observed following long cycles. Here we report the achievement of two pregnancies following long luteal phases, using ovulation induction and artificial insemination with either fresh or frozen‐thawed semen. One female SWR conceived on the first insemination attempt and gave birth to a live offspring. A second female conceived twice in consecutive long cycles although the first embryo was resorbed by 33 days post‐insemination. A pregnancy from this female's second insemination is ongoing with expected parturition in November 2019. Whether prolonged estrous cycles in SWR are subfertile or infertile in natural breeding situations remains unclear. However, our findings demonstrate that the application of ARTs following prolonged cycles can result the successful establishment of pregnancies in SWR. Therefore, with ARTs, female SWR otherwise considered nonreproductive due to long estrous cycles may still have the potential for representation and contribution to the ex situ population.

Two pregnancies were achieved following long luteal phases in two southern white rhinoceros females.

We provide evidence that long luteal phases are not necessarily infertile or early pregnancy loss.

Estradiol benzoate treatment before ovum pick-up increases the number of good quality oocytes retrieved and improves the production of transferable embryos in Japanese Black cattle

The aim of this study was to evaluate the efficacy of treatment with estradiol benzoate (EB) at luteal phase prior to the ovum pick-up (OPU) during in vitro production of transferable embryos in Japanese Black cattle. A total of 15 cows were used as oocyte donors for OPU. Of those, four donors were randomly allocated (three times) into each of two treatment groups as a crossover study, and OPU session was carried out six times per one donor. Another eleven donors were used in a paired difference test by one crossover trial. Donors in the control group received no hormonal treatment; whereas, donors in the EB group received 1 mg of EB as a single injection. First, we observed dynamics of ovarian follicles and emergence of follicular wave after EB injection using transrectal ultrasonography. The number and proportion of medium-sized follicles with 4 to 6 mm in diameter increased gradually and achieved a peak at 72 and 96 hours after EB injection. The OPU was performed 88 hours after EB injection. The EB-treated donors had a higher proportion of follicles with 4 to 6 mm in diameters at the time of OPU. The stimulation with EB significantly increased the numbers of follicles aspirated, and the good quality cumulus-oocyte complexes per OPU. Furthermore, in the EB group, the percentage of transferable blastocysts was significantly greater than that in the control group (P<0.05). In conclusion, a single EB injection before OPU increases the number of medium-sized follicles and can produce more transferable embryos.

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Efficacy of one-shot treatment with 1 mg of estradiol benzoate (EB) at luteal phase prior to the ovum pick-up (OPU) for in vitro production of transferable embryos in Japanese Black cattle was investigated.

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The donors had a higher proportion of follicles with 4 to 6 mm in diameter at 72 and 96 hours after EB i.m. injection.

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The stimulation with EB before OPU increased significantly the number of good quality cumulus-oocyte complexes, and the percentage of blastocysts or transferable embryos after in vitro fertilization.

Evaluation of three hormonal protocols for anovulatory lactating cows under regulations restricting the use of estrogenic compounds

When European Union regulations restricted the use of estrogenic compounds in food-producing animals, refined hormonal protocols were no longer applicable for anovulatory cows. However, Ovsynch and its adaptations are routinely and uniformly applied to all cows regardless of ovarian function. To evaluate their efficacy on anovulatory cows, 143, 147 and 144 anovulatory cows received Ovsynch, Presynch and G6G protocols, respectively. In comparison, 150 cyclic cows were bred without using a synchronized protocol. Results showed that cows in the Presynch group had luteolysis responding to the last prostaglandin F_2α (PGF_2α ) injection greater than the Ovsynch group. The serous progesterone levels at the first gonadotropin-releasing hormone of Ovsych and the last PGF_2α injection was greater in the G6G group than the other two hormonal treatment groups. Concentrations of Ca²⁺ and total protein in cervical mucus in all three hormone-treated groups before artificial insemination (AI) were significantly different from the controls. The G6G group obtained a greater pregnancy rate compared with Ovsynch and Presynch, but significantly less than the controls. For open cows in the Ovsynch group, estrus rate within 24 days after the first AI was significantly less than the controls. In conclusion, the G6G treatment resulted to better reproductive performance in anovulatory cows.

A weekly postpartum PGF2α protocol enhances uterine health in dairy cows

Postpartum uterine health in dairy cows is crucial for the maintenance of good reproductive performance. In order to improve uterine health and reduce puerperal intrauterine infection, 608 Holstein cows received a weekly PGF_2α protocol (3 i.m. injections of PGF_2α at 7, 14 and 21 d postpartum). For comparison, 593 cows in the control group received injections of sterile saline at the same time. Uterine score at 14 d postpartum, the prevalence of endometritis at 21-27 d postpartum, and subsequent reproduction performance was evaluated. Cows in the treated group exhibited higher tonicity (P<0.05) of the uterus, with less prevalence of endometritis (10.4%, 63/608 vs. 34.6%, 205/593; P<0.001), and required shorter time to the first AI postpartum (67.5±3.4 d vs. 84.4±3.7 d, P<0.05) and to pregnancy (114.5±5.4 d vs. 131.4±5.8 d, P<0.05). In conclusion, the present study demonstrated that uterine health in Holstein cows can be promoted while puerperal infection can be suppressed by this weekly postpartum PGF_2α protocol.