Induction of ovulation with buserelin in jennies: in search of the minimum effective dose

The Temporal Associations of B-Mode and Power-Doppler Ultrasonography, and Ovarian Steroid Changes of the Periovulatory Follicle and Corpus Luteum During Luteogenesis and Luteolysis in Jennies

This study aimed to determine the associations between B-mode and Power-doppler ultrasonography and ovarian steroids of the periovulatory follicle and respective corpus luteum (CL) during luteogenesis and luteolysis in jennies. Twenty-four periovulatory follicles/estrus of correspondent one inter-ovulatory interval (n = 12 jennies) were assessed in the study. B-mode ultrasonography and teasing were carried out once day until the detection of a periovulatory follicle (≥28 mm, uterine edema, and signs of estrus). Thereafter, jennies were monitored at 4-hour-intervals by B-mode and Power-doppler ultrasonography. Closer to ovulation, jennies were hourly checked. Each CL was checked daily from luteogenesis to luteolysis. Plasma concentrations of estradiol and progesterone were assessed daily with chemiluminescence immunoassay. Granulosa echogenicity and thickness increased from -36 hour to -1 hour before ovulation in 70% of follicles (P < .05) and were strongly associated with impending ovulation (r = 0.80 and r = 0.70, respectively). The follicular-wall blood flow increased from -72 to -24 hour pre-ovulation, while the estradiol concentration declined from 42 pg/mL by -72 hour to 31.6 pg/mL by 24 hour before ovulation (P < .05). The vascularization of the periovulatory follicle decreased from 62% (-36 hour) to 37% (-1 hour) before ovulation (P < .05). The CL vascularization and progesterone concentration gradually increased, reaching the peak at 11- and 10-day after the ovulation, respectively (P < .05). The CL vascularization started to decline 3 day before luteolysis, while progesterone concentrations started to drop 4 day before luteolysis (P < .05). In conclusion, the structural changes of the periovulatory follicle detected on B-mode and Power-doppler can be used to detect impending ovulation in donkeys; however, Power-doppler, but not B-mode ultrasonography, can be used to assess CL function in jennies.

The Kisspeptin analogue C6 induces ovulation in jennies

Kisspeptins (KPs) are the most potent stimulating neurotransmitters of GnRH release, and consequently KP administration triggers LH and/or FSH release. In small ruminants, KP or its analogs induced an LH surge followed by ovulation in both cyclic and acyclic animals, while in the mare KP only increased LH plasma levels but failed to induce ovulation. This study in jennies compares the endocrinological effects, ovulatory and pregnancy rates of the KP analog C6 and the GnRH analog buserelin acetate. The ovarian activity of nine Amiata jennies was monitored daily by transrectal ultrasound for three complete estrous cycles. Jennies in estrus were assigned, to one of three treatment groups: 50 nmol of the KP analog C6 (injected twice, 24 h apart, C6 group); 0.4 mg buserelin acetate (injected once, Bu group); and 2 mL of saline (injected once, CTRL group). Blood samples were collected at Day-1 (-24 h) Day0 (h0, before treatment), h2, h4, h6, h8, h10, h24 (before second treatment with C6), h26, h28, h30, h32, h34, h48 and every 24 h until ovulation. Jennies were inseminated once at h24 with fresh extended semen from a donkey stallion. Pregnancy diagnoses were performed 14 days after ovulation. On days 5, 10, and 14 after ovulation, for every CL the cross-sectional area (CSA) and the vascularized area (VA) were recorded by color doppler ultrasound and measured. Significantly higher plasma LH levels were found after induction between the Bu and CTRL groups at h6 and h8 (P < 0.05), while tendentially higher differences were found between the Bu/C6 groups and CTRL at h10. Five/9, 4/9, and 2/9 jennies ovulated between 24 and 48 h after induction from the Bu, C6, and CTRL groups respectively, (P > 0.05). Correlations between corpora lutea CSA and VA with serum progesterone concentration were r = 0.31, P = 0.01, r = 0.38, P = 0.01, respectively. Pregnancy rates after artificial insemination did not differ among groups (CTRL: 6/9, 66.7%; C6: 7/9, 77.8%; Bu: 6/9, 66.7%; P > 0.05). Ovulation rates after C6 treatment were comparable to that of Bu, although not different from the CTRL. Pregnancy rates were comparable to the literature in terms of fresh extended donkey semen in every group. This study suggests that stimulation of the Kp system in jennies, in contrast to findings observed in mares, induces ovulation. Further studies using higher doses and/or more animals are needed to better characterize the efficacy of C6 in jennies.

Hormonal Management for the Induction of Luteolysis and Ovulation in Andalusian Jennies: Effect on Reproductive Performance, Embryo Quality and Recovery Rate

Two prostanglandins (luprostiol, LUP, and dinoprost, DIN) and two ovulation-inducing agents (human Chorionic Gonadotropin, hCG, and deslorelin, DES) were evaluated for luteolysis and estrus induction, and for ovulation induction, respectively, in embryo donor jennies. Twenty-six fertile Andalusian jennies were used. In Experiment 1, jennies (n = 112 cycles) were randomly treated with either LUP or DIN after embryo flushing. In Experiment 2, donors (n = 84 cycles) were randomly treated with either hCG or DES to induce ovulation. No differences were found between prostaglandins for all variables studied (prostaglandin–ovulation interval (POI), interovulatory interval (IOI), embryo recovery rate (ERR), positive flushing rate (PFR) and embryo grade (EG)). The ovulation rate was similar for hCG and DES (60.9% vs. 78.7%). However, the interval to ovulation (ITO) was affected (62.61 ± 7.20 vs. 48.79 ± 2.69 h). None of the other variables studied (ERR, PFR and EG) were affected (p > 0.05), except for embryo quality (p = 0.009). In short, both prostaglandins evaluated are adequate to induce luteolysis and estrus. Both ovulation-inducing agents hastened ovulation, but DES seems to be more effective than hCG. Follicular diameter affected the interval from treatment to ovulation, and high uterine edema was related to low embryo quality.

Practical protocols for timed artificial insemination of jennies using cooled or frozen donkey semen

BACKGROUND

With the expansion of the donkey industry, timed artificial insemination (TAI) is becoming increasingly important in the reproductive management of jennies, however, TAI has not been widely investigated in donkeys.

OBJECTIVES

To develop efficient TAI protocols for cooled or frozen semen in jennies, based around ovulation induction with a GnRH analogue.

STUDY DESIGN

Experimental exploratory study.

METHODS AND RESULTS

In experiment 1, the effects of different GnRH analogue (deslorelin) doses, follicle diameter (FD) at induction, repeated use of a GnRH analogue, and the influence of season on induction efficiency, as well as distribution of ovulations over time after induction were investigated. Induction efficiency was sufficient with 2.2 mg deslorelin (≥90% ovulation within 48 hours of treatment). Ovulation rate between 24 and 48 hours was highest when the FD at treatment was 31-35 mm, as compared to 25-30 mm or 36-40 mm. Repeated use of deslorelin or treatment during different seasons had no effect on induction efficiency. About 70% of ovulations occurred between 32 and 48 hours, and highest incidence of ovulation was at 36-38 hours after induction. In experiment 2, TAI using cooled semen (1 × 10⁹ motile sperm in a 10 mL volume) was performed once at 8 hours after induction (n = 59). Pregnancy rate after TAI with cooled semen was 49.2% (29/59). In experiment 3, jennies were inseminated twice with 10 (n = 23), 5 (n = 31), 3 (n = 32), 2 (n = 82) and 1 (n = 66) straws (more than 50 × 10⁶ motile spermatozoa in each 0.5 mL straw) of frozen semen at 34 and 42 hours after induction. The pregnancy rates were 30.4%, 35.5%, 34.4%, 29.3% and 28.8%, respectively (P > 0.05).

MAIN LIMITATIONS

In the frozen semen trial, 22.5% (68/302) jennies were excluded after failure to ovulate during the appropriate time interval. In addition, there were no control groups for the AI trials.

CONCLUSION

When FD reaches 31-35 mm, a donkey jenny can be inseminated once using cooled semen at 8 hours or twice using frozen semen at 34 and 42 hours after deslorelin treatment. The frozen semen TAI protocol resulted in acceptable pregnancy rates using 1 × 10⁸ motile spermatozoa per cycle.

Hastening Time to Ejaculation in Donkey Jacks Treated with the PGF2α Analog, Cloprostenol Sodium

Simple Summary

Semen collection in donkey jacks can last up to 90 min due to the long courtship needed for this species’ males to obtain sexual excitation and erection. In several domestic animals, ProstaglandinF2α successfully stimulated excitement in the male prior to collection and enhanced semen production. In our study, the prostaglandin analog cloprostenol sodium, administered prior to the semen collection, hastened erection and ejaculation in almost all donkey jacks. No differences have been found in semen production compared to control.

Abstract

Due to the long courtship needed to attain excitation and erection, donkey semen collection can take up to 90 min. ProstaglandinF2α (PGF2α) has been reported to hasten the onset of erection and ejaculation in domesticated mammals, presumably by inducing smooth muscle contractions in the internal genitalia. However, while it has been anecdotally used in donkeys, it has yet to be critically evaluated. This study aimed to compare behavioral and semen parameters in Catalan, Balearic, Amiata, and Miranda jacks treated with the PGF2α analogue cloprostenol sodium immediately prior to exposure to an estrus jenny. Nineteen donkeys were assigned in a crossover design to receive cloprostenol sodium (125 µg, i.m.; n = 53 collections) or saline (1 mL, i.m.; n = 53 collections). There were no differences for erection (52/53 vs. 52/53) or ejaculation (52/53 vs. 48/53) for collection attempts assigned to saline or cloprostenol sodium, respectively. Cloprostenol sodium significantly hastened treatment-to-erection and treatment-to-ejaculation times from 12.0 ± 1.6 to 6.0 ± 1.6 min and from 14.0 ± 1.4 to 9.6 ± 1.4 min, respectively. Significant effects of breed and age were observed in behavioral and parameters, but there were no effects of cloprostenol sodium administration on semen parameters. In conclusion, cloprostenol sodium administration immediately prior to semen collection hastened time to collect semen in donkeys with no detrimental effects on semen quality and can be used by practitioners to circumvent long delays in donkey semen collection.

Embryo technologies in donkeys (Equus Asinus)

In industrialized countries, the donkey population had a dramatic decrease during the last century and this has brought almost all European donkey breeds to risk. Embryo technologies have already been employed as a tool for the conservation of endangered equid species (e.g. Equus Przewalskii). Today it is possible to obtain pregnancies after the transfer of donkey embryos in synchronized recipients, even though embryo transfer is not widely used as a reproductive technique in this species. So far, very few foals are born after transfer of cryopreserved embryos. To date, no pregnancies have been reported from in vitro fertilization studies. The use of the donkey as a dairy animal, as well as the increased importance of the conservation of endangered donkey breeds, could be the engine for the development and spread of embryo technologies in this species. However, funding from national and international research agencies in this field is still scarce, especially in Europe.

Comparative Efficacy of Histrelin Acetate and hCG for Inducing Ovulation in Brazilian Northeastern Jennies (Equus africanus asinus)

The goal of this study was to compare the efficiency of histrelin acetate (GnRH analog) and human chorionic gonadotropin (hCG) to hasten ovulation in Brazilian Northeastern jennies (Equus africanus asinus). Thirty cycles of ten jennies were randomly assigned in one of the three groups: G0 (control group), saline; G1, 250 μg of histrelin acetate; G2, 2500 IU of hCG. Jennies were evaluated by transrectal palpation and ultrasonography, and had the administration of an ovulation-inducing agent when a follicle measuring between 29 and 32 mm of diameter was diagnosed. Jennies were monitored every 6 hours by transrectal ultrasonography until ovulation. The interval between prostaglandin administration and ovulation was lower (P < .05) in jennies from the G1 (145.2 ± 34.6 hours) and G2 (147.4 ± 27.3 hours) groups compared with the control cycle (220.0 ± 41.8 hours). Both treatments (G1, 41.15 ± 3.5 hours; G2, 37.8 ± 2.5 hours) also reduced (P < .05) the interval that jennies took to ovulate after the administration of the ovulation-inducing agent compared with the control (81.8 ± 28.8 hours). All jennies from G1 and G2 ovulated up to 48 hours after ovulation induction, whereas 100% of jennies in the control cycle ovulated later (>48 hours from the administration of saline). In conclusion, both histrelin acetate and hCG at the used dose are efficient ovulation-inducing agents in jennies promoting ovulation up to 48 hours after administration.

Single injection of triptorelin or buserelin acetate in saline solution induces ovulation in mares the same as a single injection of hCG

The aim of this study was to assess the efficacy of different doses of buserelin acetate and another GnRH agonist, triptorelin acetate, in saline solution in a single subcutaneous injection, to induce ovulation of growing pre-ovulatory follicle in mare and compare it with the classical treatment of a single injection of hCG. The study is split into 3 experiments over different breeding seasons in the same stud with a random distribution of treatment. The first one was to compare the injection of 6 mg of buserelin with 1,500 IU of hCG; the second one consisted of comparing different doses of buserelin (6 mg and 3 mg); and the third one compared three different doses of buserelin (3, 2 and 1 mg), 0.1 mg of triptorelin with 1,500 IU of hCG as a control group. The results of all experiments showed the same efficacy between all treatments with mares ovulating between 24 and 48 hr after injection: experiment 1: hCG (78% n = 41) and buserelin 6 mg (90% n = 50); experiment 2: buserelin 6 mg (78,1% n = 192) and buserelin 3 mg (78% n = 341); and experiment 3: hCG (87% n = 106), buserelin 3 mg (84,7% n = 137), buserelin 2 mg (82,7% n = 104), buserelin 1 mg (87% n = 54) and triptorelin 0.1 mg (84,7% n = 72). In conclusion, this study contributes to erasing the dogma that has been established since 1975 that a single injection in solution without any long-acting excipient of a GnRH agonist cannot induce ovulation in the mare. This study also shows that a injection of 0.1 mg of triptorelin in solution is a good alternative for ovulation induction and is comparable to small doses of buserelin acetate in solution (1 mg) and 1,500 IU of the gold standard trigger hCG, mainly in countries where human formulation of buserelin is not available.

Key Aspects of Donkey and Mule Reproduction

Donkeys are nonseasonal, polyestrous, territorial, and nonharem breeders. Although there are many similarities between horses and donkeys, there are also reproductive features that differ, from the longer cervix in the jenny to spermatogenic efficiency in the jack. Mules display reproductive cyclic activity but are rarely fertile. Frozen donkey semen has high pregnancy rates in mares, but lower rates in jennies. This article reviews key aspects of donkey and mule reproductive physiology, reproductive medicine, and assisted reproductive techniques that are useful for practitioners offering assisted reproductive techniques, and also for practitioners with the occasional client with a basic reproductive question.

The effect of hCG, GnRH and PGF2α analogue cloprostenol on the oestrus cycle in jennies

The objectives of this study were twofold. Firstly, the present study was designed to examine susceptibility of the corpus luteum (CL) in early diestrus in jennies; and secondly, to investigate the effect of two commonly used hormonal agents in horses on the induction of ovulation in jennies. The oestrus cycles of eleven jennies were monitored by ultrasound every day. When the dominant follicle reached a diameter of 30 mm, the jennies were treated by intramuscular administration of gonadotropin-releasing hormone agonist lecirelin (GnRH, 50 µg pro toto) in the first oestrus cycle, and human chorionic gonadotropin (hCG, 1500 IU pro toto) intramuscularly in the second oestrus cycle. Prostaglandin F2α analogue cloprostenolum (PGF2α, 0.125 mg pro toto) was administered intramuscularly 2 days after the first ovulation and the interovulatory interval was monitored. This study showed that intramuscular administration of 50 µg of GnRH agonist lecirelin resulted in ovulation within 48 h in 73% of treated jennies. Intramuscular administration 1500 IU of hCG was found to be poorly effective to induce ovulation, with 36% of animals ovulating within 48 h. Intramuscular administration of PGF2α analogue cloprostenol 2 days after ovulation was unsuccessful in attempting to shorten the interovulatory interval in donkeys.

Transcriptome analysis reveals that fertilization with cryopreserved sperm downregulates genes relevant for early embryo development in the horse

Artificial insemination with cryopreserved spermatozoa is a major assisted reproductive technology in many species. In horses, as in humans, insemination with cryopreserved sperm is associated with lower pregnancy rates than those for fresh sperm, however, direct effects of sperm cryopreservation on the development of resulting embryos are largely unexplored. The aim of this study was to investigate differences in gene expression between embryos resulting from fertilization with fresh or cryopreserved sperm. Embryos were obtained at 8, 10 or 12 days after ovulation from mares inseminated post-ovulation on successive cycles with either fresh sperm or frozen-thawed sperm from the same stallion, providing matched embryo pairs at each day. RNA was isolated from two matched pairs (4 embryos) for each day, and cDNA libraries were built and sequenced. Significant differences in transcripts per kilobase million (TPM) were determined using (i) genes for which the expression difference between treatments was higher than 99% of that in the random case (P < 0.01), and (ii) genes for which the fold change was ≥ 2, to avoid expression bias in selection of the candidate genes. Molecular pathways were explored using the DAVID webserver, followed by network analyses using STRING, with a threshold of 0.700 for positive interactions. The transcriptional profile of embryos obtained with frozen-thawed sperm differed significantly from that for embryos derived from fresh sperm on all days, showing significant down-regulation of genes involved in biological pathways related to oxidative phosphorylation, DNA binding, DNA replication, and immune response. Many genes with reduced expression were orthologs of genes known to be embryonic lethal in mice. This study, for the first time, provides evidence of altered transcription in embryos resulting from fertilization with cryopreserved spermatozoa in any species. As sperm cryopreservation is commonly used in many species, including human, the effect of this intervention on expression of developmentally important genes in resulting embryos warrants attention.

Histrelin acetate-induced ovulation in Brazilian Northeastern jennies (Equus asinus) with different follicle diameters

The aim of the present study was to evaluate the efficacy of a GnRH analog for induction of ovulation in Brazilian Northeastern jennies (Equus asinus) with different follicle diameters. Four consecutive estrus of 10 jennies were used in a crossover study; C (Control, n = 10) jennies were evaluated by transrectal palpation and ultrasonography until a spontaneous ovulation and the intervals between the predetermined follicular size (25-28 mm [C1], 29-32 mm [C2] and 33-36 mm [C3] follicle) and ovulation were registered. In treated cycle, jennies had the ovulation induced by 250 μg of Histrelin acetate (Strelin^®, Botupharma, Botucatu, Brazil) when respective follicle diameters 25-28 mm (T1), 29-32 mm (T2) and 33-36 mm (T3) were diagnosed. Ovulation was monitored by transrectal palpation and ultrasonography. Different follicle diameters significantly affected (P < 0.05) the interval until ovulation between control and matched treated cycles. Interval between prostaglandin administration and ovulation diagnosis was lower in jennies from T2 group (145.2 ± 34.6 h) compared with the control cycle (220.0 ± 41.8 h) and also with other treated cycles (T1 - 209.8 ± 48.0 h; T3 - 183.3 ± 33.9 h). Histrelin acetate treatment also reduces the interval between detection of predetermined follicular size and ovulation (P < 0.05) in all treated cycles groups compared with matched control group. Higher percentage (P < 0.05) of jennies had success of ovulation induction (36-48 h after Histrelin acetate injection) in all treated cycles in contrast with the matched control group. In addition, in comparison among treated cycle groups, more (P < 0.05) jennies (100%) in T2 ovulated between 36 and 48 h after ovulation induction, compared with T1 and T3, which did not differ (P > 0.05) from each other. Edema scoring and ovulation were not associated events (r = 0.0219). In conclusion, jennies with 29-32 mm follicles satisfactory responded to ovulation induction with Histrelin acetate, which allowed the shortening of interovulatory interval in all groups evaluated.