Topic:Reproduction
Reproduction in horses encompasses the biological processes and mechanisms involved in the breeding and development of equine offspring. This includes the study of reproductive anatomy, physiology, and endocrinology in both mares and stallions. Key areas of interest include the estrous cycle, ovulation, conception, gestation, and parturition. Researchers also examine factors influencing fertility, reproductive technologies such as artificial insemination and embryo transfer, and management practices that impact reproductive success. This page compiles peer-reviewed research studies and scholarly articles that explore the physiological, genetic, and environmental aspects of equine reproduction.
Advances in Holding and Cryopreservation of Equine Oocytes and Embryos. Methods for holding of oocytes and embryos during shipment as well as for their cryopreservation can greatly aid equine reproductive management. Oocytes can be held at room temperature overnight or at cooler temperatures for two nights without affecting maturation or embryo development after intracytoplasmic sperm injection. In contrast, methods for cryopreservation of equine oocytes that support high rates of embryo development have not yet been established. Equine embryos may be held overnight at temperatures from 5°C to 19°C without reduction in viability, but longer holding periods, or h...
Current Reproductive Technologies Impacting Equine Embryo Production. Numerous reproductive technologies have been developed in the past several decades, which have dramatically changed the way mares are bred. This review will focus on embryo recovery and transfer, cooled-shipped embryos, embryo freezing, oocyte freezing, oocyte collection and transfer, intracytoplasmic sperm injection (ICSI), and sexed semen. Embryo transfer procedures have been constant for many years and the costs have not changed. The major change has been the ability to store embryos at 5 C for 12-24 hours and transport them to recipient stations. Embryo freezing has become more common us...
Historical Aspects of Equine Embryo Transfer. Early embryo transfer in equids was undertaken simultaneously in the early 1970s in Cambridge, England, and Kyoto, Japan. Both groups achieved limited success when flushing the uterine horn ipsilateral to the side of ovulation but the rates improved markedly when the whole uterus was flushed on realization of the continued movement of the embryo throughout the uterine lumen after day 6. Initial transfers of embryos to recipient mares were carried out surgically, but nonsurgical transfer via the cervix has been used subsequently with increasing success, culminating in pregnancy rates of 75%-90%...
Motility and Fertility Evaluation of Thawed Frozen Stallion Semen After 24 Hours of Cooled Storage. Breeding mares with cryopreserved semen requires specialized equipment for storage and thawing and more intensive mare management. The objectives of this study were (1) evaluate the longevity of frozen stallion semen once it had been thawed, extended, and maintained at 5°C for 48 hours in a passive cooling container, and (2) determine fertility potential of frozen semen that had been thawed, extended, and used to inseminate mares after 24 hours of cooled storage. Eight ejaculates were collected and aliquots were cooled in either INRA96 and CryoMax LE minus cryoprotectant at a concentration ...
Age-Dependent Effect of Foal Heat Breeding on Pregnancy and Embryo Mortality Rates in Thoroughbred Mares. The aim of the present study was to evaluate the correlation of age and heat cycle to determine reproductive efficiency in young and aged Thoroughbred mares bred on foal heat (FH) or on second heat (SH) after foaling. Embryo mortality (EmbM) was determined every time a mare was found open after a positive pregnancy diagnosis. Parturition to breeding interval, pregnancy rate (PregR) and EmbM rate were the dependent variables and the treatments were breeding on the FH or on SH. The cutoff age to obtain above-average probability for the EmbM was 10 years old. PregR in mares bred on FH was lower ...
Immunological memory and tolerance at the maternal-fetal interface: Implications for reproductive management of mares. The development of placentation that coincided with the evolution of mammals presented new challenges to the transmission of life from one generation to the next, particularly with regard to the possibility of maternal immunological recognition and destruction of the developing conceptus. The balance between immunity and tolerance dominates the immunological relationship between mother and fetus during mammalian pregnancy, and the focal point of this relationship lies at the interface between the trophoblast cells that comprise the outermost layer of the placenta and the maternal endometrial t...
Comparison of different mathematical models to assess seasonal variations in the longevity of DNA integrity of cooled-stored stallion sperm. Dynamic assessment of sperm DNA fragmentation (SDF) has shown to give fuller understanding of stallion semen quality; however, there have been limited attempts to use this parameter to investigate seasonal changes in productive functions. The aims of this study were to: (a) establish a reliable mathematical model to describe the longevity of cooled-stored sperm DNA integrity; (b) to examine the effect of seasonal variations on SDF. Ejaculates were cooled to 5°C, and SDF was analysed after 0, 6 and 24 hr of storage. The coefficient of determination (R ) was calculated after fine-tuning linear...
Characterization of A Homozygous Deletion of Steroid Hormone Biosynthesis Genes in Horse Chromosome 29 as A Risk Factor for Disorders of Sex Development and Reproduction. Disorders of sex development (DSD) and reproduction are not uncommon among horses, though knowledge about their molecular causes is sparse. Here we characterized a ~200 kb homozygous deletion in chromosome 29 at 29.7-29.9 Mb. The region contains genes which function as ketosteroid reductases in steroid hormone biosynthesis, including androgens and estrogens. Mutations in genes are associated with human DSDs. Deletion boundaries, sequence properties and gene content were studied by PCR and whole genome sequencing of select deletion homozygotes and control animals. Deletion analysis by PCR in ...
Energy metabolism of the equine cumulus oocyte complex during in vitro maturation. Horses are one of the few species, beside humans, in which assisted reproductive technology has important clinical applications. Furthermore, the horse can serve as a valuable model for the study of comparative reproductive biology. Here we present the first comprehensive characterisation of energy metabolism and mitochondrial efficiency in equine cumulus-oocyte complexes (COCs) during in vitro maturation (IVM), as determined using a combination of non-invasive consumption and release assays and mitochondrial function analysis. These data reveal notable species-specific differences in the rate...
Assessment of the immunocrit method to detect failure of passive immunity in newborn foals. In newborn foals the absorption of colostrum immunoglobulins in the small intestine is maximal up to 8 hours after birth and then progressively decreases to become null after 24 hours post-partum. Thus, equine practitioners need a simple, quick, inexpensive and reliable field test to identify foals affected by failure of passive transfer rather than an accurate method yielding quantitative results within the whole range of immunoglobulin concentrations. Objective: As the validity of the immunocrit method to detect failure of passive transfer in foals had not been evaluated before, the object...
SNPs analysis of height traits in Ningqiang pony. Ningqiang pony is one of the five pony breeds in China and is listed as a rare species. It is, therefore, meaningful to conduct stature research on this breed for its efficient reproduction, utilization and protection. This study is based on four SNP variants of adjacent LCORL/NCAPG, HMGA2, ZFAT and LASP1 genes, which have been found to be associated with horse height, and then, the 4 SNP loci in 22 Ningqiang ponies were analyzed. The results showed that there were genetic variations at the four loci in Ningqiang pony, there was a SNP on LCORL/NCAPG, HMGA2 and ZFAT gene all including T allele ...
Domestic Foal Weaning: Need for Re-Thinking Breeding Practices? Artificial weaning is a standard practice known to be one of the most stressful events in a domestic foal's life. Research has mainly focused on ways to alleviate weaning stress. However, there is still a need for more detailed research on what should constitute best practices with respect to animal welfare. The aim of this review is to address this issue by examining the natural weaning process. We first provide an overview of the scientific literature on the natural temporal dynamics of the dam-offspring bond in horses: it is to be noted that the natural process of weaning is little document...
Seasonal variations in sperm DNA fragmentation and pregnancy rates obtained after artificial insemination with cooled-stored stallion sperm throughout the breeding season (spring and summer). The aim of this study was to assess seasonal variations during different periods of the breeding season (spring and summer) on stallion sperm DNA fragmentation and in vivo fertility associated with cooled-stored semen samples. Ejaculates were collected from eleven stallions and assessed for sperm motility (assessed by computer-assisted sperm analysis) and plasma membrane integrity (evaluated under fluorescence microscopy). Sperm DNA fragmentation (evaluated by the Sperm Chromatin Dispersion test) was assessed in cooled-stored semen at 5 °C for up to 24 h. Artificial insemination was perfor...
Comparative Transcriptomics Analysis of Testicular miRNA from Cryptorchid and Normal Horses. In the biological process of testicular spermatogenesis, the expression and interaction of many genes are regulated by microRNAs (miRNAs). However, comparisons of miRNA expression between descended testes (DTs) and undescended testes (UDTs) are rarely done in horses. In this study, we selected two UDTs (CKY2b and GU4b) from Chakouyi (CKY) and Guanzhong (GU) horses and eight DTs (GU1-3, CKY1, CKY3, CKY2a, GU4a, and GU5). Three groups were compared to evaluate expression patterns of testicular miRNA in stallion testes. Group 1 compared normal CKY horses and GU horses (CKY1 and CKY3 vs. GU1-3). G...
Serological survey of Neospora spp. and Besnoitia spp. in horses in Portugal. Equine neosporosis is regarded to be caused either by Neospora hughesi or Neospora caninum and equine besnoitiosis is caused by Besnoitia bennetti, both of which are apicomplexan parasites. N. caninum is the only known Neospora species in Europe, where equine N. caninum infections have been reported as being associated to abortion and reproductive failure. N. hughesi is prevalent in North America and was predominantly linked to neurological disorders. B. bennetti is considered an emergent disease in donkeys in North America and evidence for B. bennetti infection was recently reported in Europe...
Persistent Breeding-Induced Endometritis in Mares – a Multifaceted Challenge: From Clinical Aspects to Immunopathogenesis and Pathobiology. Post-breeding endometritis (i.e., inflammation/infection of the endometrium), is a physiological reaction taking place in the endometrium of mares within 48 hours post-breeding, aimed to clear seminal plasma, excess sperm, microorganisms, and debris from the uterine lumen in preparation for the arrival of an embryo. Mares are classified as susceptible or resistant to persistent breeding-induced endometritis (PBIE) based on their ability to clear this inflammation/infection by 48 hours post-breeding. Mares susceptible to PBIE, or those with difficulty clearing infection/inflammation, have a def...
Pregnancy loss due to amnionitis in anglo-arabian mare-Case report. The amnion is a layer of the foetal membrane that has mechanical protection function and allows expansion and growth. The diseases that affect amnion have rarely been reported in horses. Amnionitis and funiculitis have been implicated as components of abortions as observed in abortions caused by the mare reproductive loss syndrome. Here, we report an abortion at 240-day gestation of a 7-year-old Anglo-Arabian mare with a history of previous stillbirth. Blood samples from both mare and foetus were collected for serological testing. Fragments from the placenta were taken for macroscopic and hist...
Impact of the corpus luteum on survival of the developing embryo and early pregnancy in mares. It has been more than a hundred years that studies aiming to elucidate the processes involved in cyclicity and pregnancy pointed out the requirement of ovaries and corpora lutea for embryo survival and pregnancy establishment. For horses, luteal progesterone is essential for pregnancy only during the first trimester. This progestational support is complex among domestic animals as ovarian luteal function is further enhanced by the LH-action role of equine chorionic gonadotropin (eCG) starting ∼ on Day 35 of pregnancy. Increased eCG secretion leads to the formation of supplementary corpora ...
Transcriptomic analysis reveals the key regulators and molecular mechanisms underlying myometrial activation during equine placentitis†. The key event in placentitis-induced preterm labor is myometrial activation with the subsequent initiation of labor. However, the molecular mechanisms underlying myometrial activation are not fully understood in the mares. Therefore, the equine myometrial transcriptome was characterized during placentitis (290.0 ± 1.52 days of GA, n = 5) and the prepartum period (330 days of GA, n = 3) in comparison to normal pregnant mares (289.8 ± 2.18 days of GA, n = 4). Transcriptome analysis identified 596 and 290 DEGs in the myometrium during placentitis and the prepartum period, respectively...
Does Coenzyme Q10 Exert Antioxidant Effect on Frozen Equine Sperm? During semen cryopreservation, the sensitivity of equine sperm to oxidative stress is increased by the eliminated seminal plasma. Thus, antioxidant addition to the semen extender can be helpful to the sperm survival after freezing and thawing. This work aimed to test whether coenzyme Q10 (CoQ10) added in different concentrations to the INRA 82 freezing extender has antioxidant function on equine sperm to improve its fertilizing ability. Semen samples from five stallions were frozen with the extenders: (T1) INRA 82, control, (T2) T1+ 5 μM CoQ10, (T3) T1+ 25 μM CoQ10, and (T4) T1+ 50 μM Co...
Season does not have a deleterious effect on proportions of stallion seminal plasma proteins. The mechanism by which the content of the major groups of seminal plasma proteins in stallion semen changes between the breeding and non-breeding seasons remains unknown. Here, we investigated the proportions of non-heparin-binding, phosphorylcholine-binding, and heparin-binding proteins in seminal plasma with the aim of relating them to sperm quality and testosterone levels in good and bad freezer stallions. Only minor variations in the major protein groups were found between the breeding and non-breeding seasons. In the non-breeding season, a higher content of a subset of non-heparin binding...
Application of droplet digital PCR in diagnosing of X monosomy in mares. X monosomy is the most common disorder of sex development in horses. Although cytogenetic analysis is still the gold standard in the diagnosis of equine X monosomy, novel molecular techniques are being sought to quickly and reliably detect this chromosome abnormality. Objective: The goal of this study was to evaluate the usefulness of a novel variant of the PCR technique-namely, droplet digital PCR (ddPCR)-in the detection of X monosomy in mares. Methods: A proof of concept of the usefulness of ddPCR in diagnosing an abnormal number of X chromosomes in mares. Methods: We examined an infertile ...
Effects of glucose concentration in semen extender and storage temperature on stallion sperm quality following long-term cooled storage. In Experiment 1, the effects of glucose concentration in extender (0 mM, 67 mM, 147 mM, 270 mM; G0, G67, G147, and G270, respectively) and storage temperature of extended semen (5, 10, 15 and 20 °C) were evaluated after storage for up to 5 days (T0h to T120h). For all time points tested, mean total (TMOT) and progressive (PMOT) sperm motility were lower in G0 than all other treatment groups (P < 0.05). Mean curvilinear velocity (VCL) was lower in G0 than other treatment groups at all time points tested except T0h (P 0.05). Mean TMOT and PMOT, were lower for semen stored at 20 °...
X chromosome aneuploidy and micronuclei in fertile mares. Abnormalities of chromosomes are an important and well documented cause of disorders of sexual development, fertility problems and congenital anomalies in mammals. Detection of low-level 63,X/64,XX mosaicism during routine cytogenetic evaluation is a challenge because its clinical significance is not yet fully clear. This study describes the prevalence and levels of 63,X mosaicism for a cohort of fertile mares and compares the results with eight problem mares for which no clinical cause of sub-fertility was found. The study design allowed for the analysis of micronuclei which are biomarkers of...
The oxytocin-prostaglandins pathways in the horse (Equus caballus) placenta during pregnancy, physiological parturition, and parturition with fetal membrane retention. Despite their importance in mammalian reproduction, substances in the oxytocin-prostaglandins pathways have not been investigated in the horse placenta during most of pregnancy and parturition. Therefore, we quantified placental content of oxytocin (OXT), oxytocin receptor (OXTR), and prostaglandin E2 and F2 alpha during days 90-240 of pregnancy (PREG), physiological parturition (PHYS), and parturition with fetal membrane retention (FMR) in heavy draft horses (PREG = 13, PHYS = 11, FMR = 10). We also quantified OXTR and prostaglandin endoperoxide synthase-2 (PTGS2) mRNA expression ...
Structural modelling of the equine protein disulphide isomerase A1 and its quantification in the epididymis and seminal plasma. The protein disulphide isomerase A1 (PDIA1) is an important chaperone involved in protein quality control and redox regulation. Also, the ability of PDIA1 to bind to oestrogens suggests that it may play a role in epididymal maturation and male fertility. The goals of this study were to (a) verify the possible interaction between 17β-estradiol and equine PDIA1 using bioinformatics; (b) identify and quantify PDIA1 protein in equine cauda epididymis throughout peripuberty; and (c) determine whether the amounts of PDIA1 in equine seminal plasma and spermatozoa are associated with fertility. Using...
Ovarian histopathology, pre- and post-operative endocrinological analysis and behavior alterations in 27 mares undergoing bilateral standing laparoscopic ovariectomy. Determining if ovariectomy will abolish unwanted behaviors can be challenging in mares without ultrasonographic ovarian abnormalities and/or endocrine values not consistent with a granulosa cell tumor. The objective of the study was to identify mares that have a positive improvement in unwanted behaviors after elective standing laparoscopic ovariectomy and to determine if the change is associated with any pre- and post-operative endocrine profiles and/or with ovarian histological findings. During the study period 27 mares underwent a bilateral standing laparoscopic ovariectomy. Pre- and post-o...
Phenotypic and genetic analysis of reproductive traits in horse populations with different breeding purposes. Reproductive traits have a major influence on the economic effectiveness of horse breeding. However, there is little information available. We evaluated the use of reproductive traits as selection criteria in official breeding programs to increase the reproductive efficiency of breeding studs, analysing 696 690 records from the pedigree data of eight Spanish horse populations, with different breeding purposes. The reproductive parameters studied in both sexes were age at first foaling (AFF), age at last foaling, average reproductive life and generational interval. In the females, the average ...
Upregulation of CRISP-3 and kallikrein in stallion seminal plasma is associated with poor tolerance of cooled storage. For unknown reasons, stallion fertility and sperm longevity during cooled storage of semen vary markedly between individuals. Spermatozoa from individual stallions react differently to the presence, or the removal, of seminal plasma (SP). The aim was to evaluate differences in protein content in stallion seminal plasma with either a positive or a negative effect on sperm chromatin integrity during storage. Stallion semen samples from different ejaculate fractions were stored at 5°C for 24 hr. Sperm survival was assessed after storage using a sperm chromatin structure assay. Protein expressio...
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 ...