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Challenges in Equine (Assisted) Reproduction
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Challenges in Equine (Assisted) Reproduction

A special issue of Animals (ISSN 2076-2615). This special issue belongs to the section "Animal Reproduction".

Deadline for manuscript submissions: closed (31 May 2021) | Viewed by 27488

Special Issue Editor

Dr. Katrien Smits

E-Mail Website
Guest Editor
Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
Interests: horse; embryo; reproduction; pregnancy; ICSI; genetics

Special Issue Information

Dear Colleagues,

Most definitely, the horse is one of the most intriguing species when it comes to reproduction. Equine reproduction is characterized by several unique features, like the resistance to superovulation, the challenge to obtain sperm capacitation and fertilization in vitro, the selective transport of embryos through the oviduct, the formation of a glycoprotein capsule and endometrial cups,… As such, research in this field is challenging, but interesting, and it provides the basis for improved knowledge and clinical applications. This has resulted in a recent worldwide increase in the application of assisted reproductive technologies in the horse.

For this special issue, we invite original research papers that address these challenges in equine reproduction, leading to fundamental insights into equine reproduction and pregnancy and/or aiming at clinical application.

Dr. Katrien Smits
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Animals is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • horse
  • reproduction
  • pregnancy
  • embryo
  • sperm
  • hormones
  • assisted reproduction
  • ICSI

Published Papers (6 papers)

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Research

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15 pages, 1233 KiB  
Article
Anti-Müllerian Hormone and OPU-ICSI Outcome in the Mare
by Marion Papas, Jan Govaere, Sofie Peere, Ilse Gerits, Margot Van de Velde, Daniel Angel-Velez, Tine De Coster, Ann Van Soom and Katrien Smits
Animals 2021, 11(7), 2004; https://doi.org/10.3390/ani11072004 - 05 Jul 2021
Cited by 10 | Viewed by 4139
Abstract
Anti-Müllerian hormone (AMH) reflects the population of growing follicles and has been related to mammalian fertility. In the horse, clinical application of ovum pick-up and intracytoplasmic sperm injection (OPU-ICSI) is increasing, but results depend largely on the individuality of the mare. The aim [...] Read more.
Anti-Müllerian hormone (AMH) reflects the population of growing follicles and has been related to mammalian fertility. In the horse, clinical application of ovum pick-up and intracytoplasmic sperm injection (OPU-ICSI) is increasing, but results depend largely on the individuality of the mare. The aim of this study was to assess AMH as a predictor for the OPU-ICSI outcome in horses. Therefore, 103 mares with a total follicle count above 10 were included in a commercial OPU-ICSI session and serum AMH was determined using ELISA. Overall, the AMH level was significantly correlated with the number of aspirated follicles and the number of recovered oocytes (p < 0.001). Mares with a high AMH level (≥2.5 µg/L) yielded significantly greater numbers of follicles (22.9 ± 1.2), oocytes (13.5 ± 0.8), and blastocysts (2.1 ± 0.4) per OPU-ICSI session compared to mares with medium (1.5–2.5 µg/L) or low AMH levels (<1.5 µg/L), but no significant differences in blastocyst rates were observed. Yet, AMH levels were variable and 58% of the mares with low AMH also produced an embryo. In conclusion, measurement of serum AMH can be used to identify mares with higher chances of producing multiple in vitro embryos, but not as an independent predictor of successful OPU-ICSI in horses. Full article
(This article belongs to the Special Issue Challenges in Equine (Assisted) Reproduction)
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15 pages, 1160 KiB  
Article
A Modified Flotation Density Gradient Centrifugation Technique Improves the Semen Quality of Stallions with a High DNA Fragmentation Index
by Muhammad Umair, Heiko Henning, Tom A. E. Stout and Anthony Claes
Animals 2021, 11(7), 1973; https://doi.org/10.3390/ani11071973 - 01 Jul 2021
Cited by 2 | Viewed by 5070
Abstract
Sperm DNA fragmentation compromises fertilization and early embryo development. Since spermatozoa lack the machinery to repair DNA damage, to improve the likelihood of establishing a healthy pregnancy, it is preferable to process ejaculates of stallions with a high sperm DNA fragmentation index (DFI) [...] Read more.
Sperm DNA fragmentation compromises fertilization and early embryo development. Since spermatozoa lack the machinery to repair DNA damage, to improve the likelihood of establishing a healthy pregnancy, it is preferable to process ejaculates of stallions with a high sperm DNA fragmentation index (DFI) before artificial insemination or intracytoplasmic sperm injection. The aim of this study was to examine a modified flotation density gradient centrifugation (DGC) technique in which semen was diluted with a colloid solution (Opti-prepTM) to increase its density prior to layering between colloid layers of lower and higher density. The optimal Opti-prepTM solution (20–60%) for use as the bottom/cushion layer was first determined, followed by a comparison between a modified sedimentation DGC and the modified flotation DGC technique, using different Opti-prepTM solutions (20%, 25% and 30%) as the top layer. Finally, the most efficient DGC technique was selected to process ejaculates from Friesian stallions (n = 3) with high sperm DFI (>20%). The optimal Opti-prepTM solution for the cushion layer was 40%. The modified sedimentation technique resulted in two different sperm populations, whereas the modified flotation technique yielded three populations. Among the variants tested, the modified flotation DGC using 20% Opti-prepTM as the top layer yielded the best results; the average sperm recovery was 57%; the DFI decreased significantly (from 12% to 4%) and the other sperm quality parameters, including progressive and total motility, percentages of spermatozoa with normal morphology and viable spermatozoa with an intact acrosome, all increased (p < 0.05). In Friesian stallions with high sperm DFI, the modified flotation DGC markedly decreased the DFI (from 31% to 5%) and significantly improved the other semen quality parameters, although sperm recovery was low (approximately 20%). In conclusion, stallion sperm DFI and other sperm quality parameters can be markedly improved using a modified flotation DGC technique employing a 40% Opti-prepTM cushion and a 20% top layer. Full article
(This article belongs to the Special Issue Challenges in Equine (Assisted) Reproduction)
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10 pages, 866 KiB  
Article
Deslorelin Slow-Release Implants Delay Ovulation and Increase Plasma AMH Concentration and Small Antral Follicles in Haflinger Mares
by Martim Kaps, Carolina T. C. Okada, Camille M. Gautier, Jörg Aurich and Christine Aurich
Animals 2021, 11(6), 1600; https://doi.org/10.3390/ani11061600 - 28 May 2021
Cited by 2 | Viewed by 3157
Abstract
There is an increasing interest in the manipulation of ovarian follicular populations in large domestic animals because this could prove beneficial for assisted reproductive techniques such as ovum pick-up (OPU). The aim of the present study was to evaluate the effects of deslorelin [...] Read more.
There is an increasing interest in the manipulation of ovarian follicular populations in large domestic animals because this could prove beneficial for assisted reproductive techniques such as ovum pick-up (OPU). The aim of the present study was to evaluate the effects of deslorelin slow-release implants (SRI) on the interovulatory interval, antral follicle count (AFC), number of follicles of different size ranges and plasma anti-Muellerian hormone (AMH) concentration in mares. To synchronize their estrous cycles, Haflinger mares (n = 12) were treated twice with a PGF2α analogue. One day after the second injection (day 0), mares received a 9.4 mg deslorelin SRI (group DES, n = 6) or 1.25 mg deslorelin in a short-acting formulation (CON; n = 6), respectively. Regular transrectal ultrasonography of the genital tract was performed and blood samples were collected for the analysis of progesterone, AMH and gonadotrophins. The interval from implant insertion to the first spontaneous ovulation was 23.8 ± 10.5 days in group DES compared to 17.0 ± 3.9 days in group CON (p < 0.05). For the concentrations of LH, FSH and AMH, interactions between time and treatment were detected (p < 0.05). The AFC and the mean number of follicles with 5 to 10, 10 to 15 and 15 to 20 mm in diameter changed over time (p < 0.05). A time x treatment interaction was demonstrated for follicles of 10 to 15 mm in diameter (p < 0.05). The changes in this follicular subpopulation were reflected by increased plasma AMH concentration in group DES. In conclusion, 9.4 mg deslorelin implants show minor effects with regard to estrus suppression in mares, whereas the changes in the subpopulation of small ovarian follicles could be a promising tool for preparation of mares for OPU. Full article
(This article belongs to the Special Issue Challenges in Equine (Assisted) Reproduction)
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12 pages, 817 KiB  
Article
Overfeeding Extends the Period of Annual Cyclicity but Increases the Risk of Early Embryonic Death in Shetland Pony Mares
by Nicky M. M. D’Fonseca, Charlotte M. E. Gibson, Iris Hummel, David A. van Doorn, Ellen Roelfsema, Tom A. E. Stout, Jan van den Broek and Marta de Ruijter-Villani
Animals 2021, 11(2), 361; https://doi.org/10.3390/ani11020361 - 01 Feb 2021
Cited by 4 | Viewed by 1840
Abstract
Obesity has been associated with altered reproductive activity in mares, and may negatively affect fertility. To examine the influence of long-term high-energy (HE) feeding on fertility, Shetland pony mares were fed a diet containing 200% of net energy (NE) requirements during a three-year [...] Read more.
Obesity has been associated with altered reproductive activity in mares, and may negatively affect fertility. To examine the influence of long-term high-energy (HE) feeding on fertility, Shetland pony mares were fed a diet containing 200% of net energy (NE) requirements during a three-year study. The incidence of hemorrhagic anovulatory follicles (HAF) and annual duration of cyclicity were compared to those in control mares receiving a maintenance diet. Day-7 embryos were flushed and transferred between donor and recipient mares from both groups; the resulting conceptuses were collected 21 days after transfer to assess conceptus development. HE mares became obese, and embryos recovered from HE mares were more likely to succumb to early embryonic death. The period of annual cyclicity was extended in HE compared to control mares in all years. The incidence of HAFs did not consistently differ between HE and control mares. No differences in embryo morphometric parameters were apparent. In conclusion, consuming a HE diet extended the duration of cyclicity, and appeared to increase the likelihood of embryos undergoing early embryonic death following embryo transfer. Full article
(This article belongs to the Special Issue Challenges in Equine (Assisted) Reproduction)
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9 pages, 699 KiB  
Article
Diestrous Ovulations in Pregnant Mares as a Response to Low Early Postovulatory Progestogen Concentration
by Carolina T. C. Okada, Martim Kaps, Javier Perez Quesada, Camille Gautier, Jörg Aurich and Christine Aurich
Animals 2020, 10(12), 2249; https://doi.org/10.3390/ani10122249 - 30 Nov 2020
Cited by 3 | Viewed by 1759
Abstract
Spontaneous prolongation of the luteal phase has been described in horses, but the underlying causes are still unclear. The present study investigated details of gonadotrophin and progestogen secretion in pregnant mares (n = 11) with or without experimentally reduced early postovulatory luteal function. [...] Read more.
Spontaneous prolongation of the luteal phase has been described in horses, but the underlying causes are still unclear. The present study investigated details of gonadotrophin and progestogen secretion in pregnant mares (n = 11) with or without experimentally reduced early postovulatory luteal function. From days 0 to 3 after ovulation, they were treated with the prostaglandin F2α (PGF2α) analogue cloprostenol or left untreated. After conceptus collection on day 34, they were assigned to the opposite treatment. Mares were affiliated to the group primary corpus luteum (n = 6) or diestrous corpus luteum (n = 5) depending on diestrous corpus luteum (CL) detection in the PGF pregnancy. For statistical comparisons, a p-value < 0.05 was significant. There was an effect of treatment (p < 0.01), but not of group on progestogen concentration. The concentration of LH was higher in PGF-treated than in untreated pregnancies (p < 0.05), but did not differ between groups. The FSH concentration did not differ between groups nor treatments. The total luteal tissue area was greater in mares with a diestrous ovulation during the PGF treatment pregnancy. Low progestogen concentration in the early postovulatory phase diminish the negative feedback on the hypothalamic-pituitary axis in early pregnancy and, thus, stimulate a luteal tissue response. Detection of secondary CL at the time of pregnancy examination in mares may reflect that early post-ovulatory progestogen concentrations were low. Full article
(This article belongs to the Special Issue Challenges in Equine (Assisted) Reproduction)
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Review

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32 pages, 2201 KiB  
Review
The Mare: A Pertinent Model for Human Assisted Reproductive Technologies?
by Achraf Benammar, Emilie Derisoud, François Vialard, Eric Palmer, Jean Marc Ayoubi, Marine Poulain and Pascale Chavatte-Palmer
Animals 2021, 11(8), 2304; https://doi.org/10.3390/ani11082304 - 04 Aug 2021
Cited by 17 | Viewed by 9186
Abstract
Although there are large differences between horses and humans for reproductive anatomy, follicular dynamics, mono-ovulation, and embryo development kinetics until the blastocyst stage are similar. In contrast to humans, however, horses are seasonal animals and do not have a menstrual cycle. Moreover, horse [...] Read more.
Although there are large differences between horses and humans for reproductive anatomy, follicular dynamics, mono-ovulation, and embryo development kinetics until the blastocyst stage are similar. In contrast to humans, however, horses are seasonal animals and do not have a menstrual cycle. Moreover, horse implantation takes place 30 days later than in humans. In terms of artificial reproduction techniques (ART), oocytes are generally matured in vitro in horses because ovarian stimulation remains inefficient. This allows the collection of oocytes without hormonal treatments. In humans, in vivo matured oocytes are collected after ovarian stimulation. Subsequently, only intra-cytoplasmic sperm injection (ICSI) is performed in horses to produce embryos, whereas both in vitro fertilization and ICSI are applied in humans. Embryos are transferred only as blastocysts in horses. In contrast, four cells to blastocyst stage embryos are transferred in humans. Embryo and oocyte cryopreservation has been mastered in humans, but not completely in horses. Finally, both species share infertility concerns due to ageing and obesity. Thus, reciprocal knowledge could be gained through the comparative study of ART and infertility treatments both in woman and mare, even though the horse could not be used as a single model for human ART. Full article
(This article belongs to the Special Issue Challenges in Equine (Assisted) Reproduction)
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