Special Issue "Challenges in the Reproduction of Equids"

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

Deadline for manuscript submissions: 30 November 2021.

Special Issue Editor

Prof. Dr. Christine Aurich
E-Mail Website
Guest Editor
Artificial Insemination and Embryo Transfer, Department for Small Animals and Horses, Vetmeduni Vienna, Veterinärplatz 1, 1210 Vienna, Austria
Interests: equine reproduction; gonadal function and dysfunction; early pregnancy; late pregnancy and parturition

Special Issue Information

Dear Colleagues,

Horses are selecting for breeding purposes either because of their performance or appearance, but fertility is often neglected. This contributes to low fertility in equine reproduction. More recently, also fertility problems in donkeys have raised an increasing interest. During the past few decades, studies have focused on better understanding the mechanisms that regulate the reproductive processes in equids. There are, however, still many aspects of equine reproduction that remain unknown or have not yet been proven. Many published studies have answered some of these questions but have also raised new ones, and several of those questions are still unanswered.

This Special Issue aims to improve our understanding of reproduction in equids; therefore, we invite high-quality and original research or review papers that address new insights on this topic, with main focus on the physiology and pathology of equine and donkey reproduction.

Prof. Christine Aurich
Guest Editor

Manuscript Submission Information

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Keywords

  • equine reproduction
  • gonadal function and dysfunction
  • early pregnancy
  • late pregnancy and parturition

Published Papers (3 papers)

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Research

Article
Sexual Differentiation and Primordial Germ Cell Distribution in the Early Horse Fetus
Animals 2021, 11(8), 2422; https://doi.org/10.3390/ani11082422 - 17 Aug 2021
Viewed by 639
Abstract
It was the aim of this study to characterize the development of the gonads and genital ducts in the equine fetus around the time of sexual differentiation. This included the identification and localization of the primordial germ cell population. Equine fetuses between 45 [...] Read more.
It was the aim of this study to characterize the development of the gonads and genital ducts in the equine fetus around the time of sexual differentiation. This included the identification and localization of the primordial germ cell population. Equine fetuses between 45 and 60 days of gestation were evaluated using a combination of micro-computed tomography scanning, immunohistochemistry, and multiplex immunofluorescence. Fetal gonads increased in size 23-fold from 45 to 60 days of gestation, and an even greater increase was observed in the metanephros volume. Signs of mesonephros atrophy were detected during this time. Tubular structures of the fetal testes were present from day 50 onwards, whereas cell clusters dominated in the fetal ovary. The genital ducts were well-differentiated and presented a lumen in all samples. No sign of mesonephric or paramesonephric duct degeneration was detected. Expression of AMH was strong in the fetal testes but absent in ovaries. Irrespective of sex, primordial germ cells selectively expressed LIN28. Migration of primordial germ cells from the mesonephros to the gonad was detected at 45 days, but not at 60 days of development. Their number and distribution within the gonad were influenced (p < 0.05) by fetal sex. Most primordial germ cells (86.8 ± 3.2% in females and 84.6 ± 4.7% in males) were characterized as pluripotent according to co-localization with CD117. However, only a very small percentage of primordial germ cells were proliferating (7.5 ± 1.7% in females and 3.2 ± 1.2% in males) based on co-localization with Ki67. It can be concluded that gonadal sexual differentiation in the horse occurs asynchronously with regard to sex but already before 45 days of gestation. Full article
(This article belongs to the Special Issue Challenges in the Reproduction of Equids)
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Article
Epigenetic Changes in Equine Embryos after Short-Term Storage at Different Temperatures
Animals 2021, 11(5), 1325; https://doi.org/10.3390/ani11051325 - 06 May 2021
Viewed by 420
Abstract
In embryos subjected to assisted reproductive techniques, epigenetic modifications may occur that can influence embryonic development and the establishment of pregnancy. In horses, the storage temperature during transport of fresh embryos before transfer is a major concern. The aim of this study was, [...] Read more.
In embryos subjected to assisted reproductive techniques, epigenetic modifications may occur that can influence embryonic development and the establishment of pregnancy. In horses, the storage temperature during transport of fresh embryos before transfer is a major concern. The aim of this study was, therefore, to determine the effects of two storage temperatures (5 °C and 20 °C) on equine embryos, collected at day seven after ovulation and stored for 24 h, on: (i) morphological development; (ii) expression of candidate genes associated with embryo growth and development, maternal recognition of pregnancy, methylation and apoptosis, and (iii) gene-specific and global DNA methylation. Embryos (n = 80) were collected on day seven or day eight after ovulation and assigned to four groups: day seven control (E7F, fresh); day seven, stored for 24 h at 5 °C (E5C); day seven, stored for 24 h at 20 °C (E20C) and day eight control (E8F, fresh 24h time control). The embryos and the storage medium (EquiHold, holding medium, Minitube, Tiefenbach, Germany) from all treatment groups were analyzed for (i) medium temperature, pH, and lipid peroxidation (malondialdehyde; MDA) and (ii) embryo morphology, mRNA expression and DNA methylation (immunohistochemistry and gene-specific DNA methylation). The size of embryos stored at 5 °C was larger (p < 0.01), whereas embryos stored at 20 °C were smaller (p < 0.05) after 24 h. There were no changes in pH and MDA accumulation irrespective of the group. The mRNA expression of specific genes related to growth and development (POU5F1, SOX2, NANOG), maternal recognition of pregnancy (CYP19A1, PTGES2), DNA methylation (DNMT1, DNMT3A, DNMT3B) and apoptosis (BAX) in the E5C and E20C were either up or downregulated (p < 0.05) when compared to controls (E7F and E8F). The immune expression of 5mC and 5hmC was similar among treatment groups. Percentage of methylation in the CpG islands was lower in the specific genes ESR1, NANOG and DNMT1 (p < 0.001) in E20C embryos when compared to E8F (advanced embryo stage). Therefore, our study demonstrates for the first time the gene-specific and global DNA methylation status of fresh equine embryos collected on days seven and eight after ovulation. Although our results suggest some beneficial effects of storage at 20 °C in comparison to 5 °C, the short-term storage, regardless of temperature, modified gene expression and methylation of genes involved in embryo development and may compromise embryo viability and development after transfer. Full article
(This article belongs to the Special Issue Challenges in the Reproduction of Equids)
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Article
Expression of Enzymes Associated with Prostaglandin Synthesis in Equine Conceptuses
Animals 2021, 11(4), 1180; https://doi.org/10.3390/ani11041180 - 20 Apr 2021
Cited by 2 | Viewed by 475
Abstract
In the horse, mobility of the conceptus is required for maternal recognition of pregnancy depending on secretion of prostaglandins by the conceptus. The aim of this study was to determine the expression and localization of key enzymes of the different pathways leading to [...] Read more.
In the horse, mobility of the conceptus is required for maternal recognition of pregnancy depending on secretion of prostaglandins by the conceptus. The aim of this study was to determine the expression and localization of key enzymes of the different pathways leading to synthesis of prostaglandin E2 and F2α in the equine conceptus during the mobility phase. Enzyme expression was analyzed via quantitative RT-PCR in total RNA samples of equine conceptuses collected on days 10 (n = 5), 12 (n = 12), 14 (n = 5) and 16 (n = 7) from healthy mares. Relative abundance of cyclooxygenase (COX)-2 mRNA was higher (p < 0.05) than of COX-1 irrespective of conceptus age and for phospholipase A2 on day 16 in comparison to all other days (p < 0.01). Abundance of mRNA of cytosolic and microsomal prostaglandin E synthase (PGES) and of carbonyl reductase (CBR) 1 was not influenced by conceptus age. Immunohistochemically, COX-1, COX-2, as well as cytosolic and microsomal PGES were present in both the ectodermal and endodermal layer of the yolk sac wall. CBR-1 was restricted to periembryonic disc area. The localisation of the key enzymes explains the mechanism of embryo mobility. In vitro incubation of primary trophoblast cell cultures with oxytocin had no effect on key enzyme synthesis. Full article
(This article belongs to the Special Issue Challenges in the Reproduction of Equids)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: probably with content regarding the correlation of various sperm quality assays with fertility
Authors: Anders Johannisson
Affiliation: Swedish University of Agricultural Sciences, Clinical Sciences, Uppsala, Sweden
Abstract: probably with content regarding the correlation of various sperm quality assays with fertility

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