Single-cell atlas of the pregnant equine endometrium before and after implantation.

Embryo implantation in the mare occurs just over one month after fertilization, coinciding with the production of chorionic gonadotropin. The factors that regulate this late implantation in the mare, and whether they are unique to horses or shared with more invasive embryo implantation in other species, remain poorly understood. This study aimed to determine and compare the transcriptome and subpopulations of endometrial cells before and after embryo implantation in the horse.

Naturally occurring horse model of miscarriage reveals temporal relationship between chromosomal aberration type and point of lethality.

Chromosomal abnormalities are a common cause of human miscarriage but rarely reported in any other species. As a result, there are currently inadequate animal models available to study this condition. Horses present one potential model since mares receive intense gynecological care.

Monoclonal antibodies for equine CD25 improve detection of regulatory T cells in horses.

CD25, the interleukin-2 receptor α-chain, is expressed on cell surfaces of different immune cells and is commonly used for phenotyping of regulatory T cells (Tregs). CD25 has essential roles in the maintenance of hemostasis and immune tolerance and Treg cell involvement has been shown in human diseases and murine models for allergy, autoimmunity, cancer, chronic inflammation, and many others. In horses, a cross-reactive anti-human CD25 antibody has previously been used for characterizing Tregs.

Prevalence of Microbial Isolates Cultured from Endometrial Swab Samples Collected from United Kingdom Thoroughbred Mares from 2014 to 2020.

Determining whether endometrial microbial isolates are pathogens, contaminants, or even part of the "normal" microbiome is extremely complex, particularly given the absence of "gold standard" tests for endometritis. Population-level benchmarking and temporal monitoring can provide novel insights and a wider context to improve understanding. This study aimed to (i) estimate the prevalence of endometrial isolates from swabs of Thoroughbred broodmares in Newmarket, UK between 2014 and 2020; and (ii) evaluate the effects of year, mare age, and cytology findings on isolate prevalence.

Does inbreeding contribute to pregnancy loss in Thoroughbred horses?

Background: Excessive inbreeding increases the probability of uncovering homozygous recessive genotypes and has been associated with an increased risk of retained placenta and lower semen quality. No genomic analysis has investigated the association between inbreeding levels and pregnancy loss.

Objectives: To compare genetic inbreeding coefficients (F) of naturally occurring Thoroughbred Early Pregnancy Loss (EPLs), Mid and Late term Pregnancy Loss (MLPL) and Controls.

The equine umbilical cord in clinically healthy pregnancies.

Background: Excessive umbilical cord length (UCL) is associated with equine pregnancy loss. However, a lack of UCL reference values makes it difficult to define excessive UCL. Further, factors associated with differences in UCL are poorly understood.

Gestation Length is Associated With Early-Life Limb Deformities in Thoroughbred Foals.

Flexural and angular limb deformities (LD) are an important cause of early-life morbidity and mortality/euthanasia in Thoroughbred foals. The majority are congenital in origin but, to date, their precise aetiology is poorly understood. We hypothesized that maternal- and pregnancy-level factors, particularly those with potential to influence in-utero growth and development, could play an important role.

Production of Mare Chorionic Girdle Organoids That Secrete Equine Chorionic Gonadotropin.

The equine chorionic girdle is comprised of specialized invasive trophoblast cells that begin formation approximately 25 days after ovulation (day 0) and invade the endometrium to become endometrial cups. These specialized trophoblast cells transition from uninucleate to differentiated binucleate trophoblast cells that secrete the glycoprotein hormone equine chorionic gonadotropin (eCG; formerly known as pregnant mare serum gonadotropin or PMSG). This eCG has LH-like activity in the horse but variable LH- and FSH-like activity in other species and has been utilized for these properties both in vivo and in vitro.

Incidence of disease, injury and death in Thoroughbred foals and yearlings on stud farms in the UK and Ireland.

Background: Up-to-date estimates of early-life morbidity and mortality in Thoroughbreds are lacking.

Methods: A birth cohort was established on Thoroughbred stud farms across the UK and Ireland. All veterinary interventions for disease or injury between birth and 18 months of age or leaving the study were recorded.

Antimicrobial resistance of endometrial bacterial isolates collected from UK Thoroughbred mares between 2014 and 2020.

Background: Antimicrobial resistance (AMR) is important in equine reproduction, as antimicrobials have historically been widely used in the management of breeding mares. However, evidence of the characteristics of AMR in uterine isolates is limited in the UK. The objective of this retrospective study was therefore to describe temporal changes in AMR patterns of bacteria isolated from the endometrium of Thoroughbred broodmares in south-east England between 2014 and 2020.

Lethal variants of equine pregnancy: is it the placenta or foetus leading the conceptus in the wrong direction?

Embryonic and foetal loss remain one of the greatest challenges in equine reproductive health with 5-10% of established day 15 pregnancies and a further 5-10% of day 70 pregnancies failing to produce a viable foal. The underlying reason for these losses is variable but ultimately most cases will be attributed to pathologies of the environment of the developing embryo and later foetus, or a defect intrinsic to the embryo itself that leads to lethality at any stage of gestation right up to birth. Historically, much research has focused on the maternal endometrium, endocrine and immune responses in pregnancy and pregnancy loss, as well as infectious agents such as pathogens, and until recently very little was known about the both small and large genetic variants associated with reduced foetal viability in the horse.

Populations of NK Cells and Regulatory T Cells in the Endometrium of Cycling Mares-A Preliminary Study.

Endometrial immune cells are essential to support uterine functions across the estrous cycle and in preparation for pregnancy. It has been acknowledged that changes in phenotype and/or numbers of lymphocytes, such as regulatory T cells (Tregs) and NK cells, might result in lower fertility in women and mice. Little is known about equine endometrial immune cells across the estrous cycle.

Multivariable analysis to determine risk factors associated with abortion in mares.

Risk factors associated with equine reproductive efficiency have been identified along with those associated specifically with early pregnancy loss (EPL). In contrast, no studies have reported risk factors associated with abortion (loss between day 70 and 300 post-cover). Given the causes of abortion differ to those of EPL, likely too will the risk factors.

Bayesian accuracy estimates and fit for purpose thresholds of cytology and culture of endometrial swab samples for detecting endometritis in mares.

The overall aim of this work was to identify the potential impact of misclassification errors associated with routine screening and diagnostic testing for endometritis in mares. Using Bayesian latent class models (BLCM), specific objectives were to: 1) estimate the diagnostic accuracy of cytology and culture of endometrial swab samples to detect endometritis in mares; 2) assess the impact of different cytology thresholds on test accuracy and misclassification costs; and 3) assess the sensitivity (Se) and specificity (Sp) of a diagnostic strategy including both tests interpreted in series and parallel. Diagnostic and pre-breeding endometrial swab samples collected from 3448 mares based at breeding premises located in the South East of England between 2014 and 2020 were retrospectively analysed.

Date of birth and purchase price as foals or yearlings are associated with Thoroughbred flat race performance in the United Kingdom and Ireland.

Background: Thoroughbred breeders aim to have foals born early in the season, but scientific evidence on the advantages for race performance is scarce and contradictory.

Methods: The association between date of birth and purchase price as foal/yearling, with race performance by the end of the second and third years of life of Thoroughbreds racing in flat races in the United Kingdom (UK) and Ireland (IRE) was assessed using negative binomial and zero-inflated negative binomial models on the entire 2014-2015 UK/IRE foal crops ( = 28,282).

Results: In total, 6666 and 9456 horses raced in UK/IRE flat racing by the end of their second and third years of life.

Mixed-Effects Modelling of the Risk Factors Associated with Multiple Pregnancies in Thoroughbred Mares.

Multiple pregnancies (MPs) are commonly diagnosed during breeding management of mares. Whilst some studies have reported on factors associated with the risk of MPs, few have utilised multivariable data analysis to control for confounding variables. A prospective cohort study of Thoroughbred broodmares was conducted with information collected on 27 factors.

Environmental constraints and pathologies that modulate equine placental genes and development.

Equine placental development is a long process with unique features. Implantation occurs around 40 days of gestation (dpo) with the presence of a transient invasive placenta from 25-35 to 100-120 dpo. The definitive, non-invasive placenta remains until term (330 days).

First reported case of fragile foal syndrome type 1 in the Thoroughbred caused by PLOD1 c.2032G>A.

Background: Warmblood Fragile Foal Syndrome Type 1 (WFFS) is an autosomal recessive disorder reported previously only in warmbloods and thought to be caused by a variant in the gene procollagen-lysine,2-oxoglutarate 5-dioxygenase 1 (PLOD1, c.2032G>A, p.Gly678Arg).

Preliminary testing of psychometric properties of the 'student perceptions of veterinary interprofessional education and work scale' (SP-VIEWS).

Responsibility for the provision of veterinary care and services is increasingly shared between veterinary surgeons/veterinarians and registered veterinary nurses/veterinary technicians. Interprofessional education of these clinical professionals is not widespread but is growing. Understanding students' perceptions of veterinary interprofessional education and working is therefore important; however, no validated scale exists to assess this.

Retrospective analysis of the population dynamics and racing outcomes of the 2014 and 2015 UK and Ireland Thoroughbred foal crops.

Background: Up-to-date figures on early losses of Thoroughbreds from the racing industry can inform strategies to improve retention and incentivise traceability of Thoroughbreds during this early life period.

Methods: Data on Thoroughbred mares bred in 2013-2014 and training, racing and sales information of their live offspring were analysed. The proportions and 95% confidence intervals (95% CI) of the entire 2014-2015 United Kingdom and Ireland foal crops that entered training, raced, were imported and/or exported between birth and the end of their third year of life, as well as the racing performance of these horses as 2- and 3-year-olds were described.

Incidence and causes of pregnancy loss after Day 70 of gestation in Thoroughbreds.

Background: Pregnancy loss after Day 70 of gestation manifests as abortion, stillbirth or perinatal death. While previous studies have reported the diagnoses of laboratory submissions, none have quantified the incidence and causes of abortions, stillbirths and perinatal mortality at a population level.

Objectives: To report the incidence and causes of pregnancy loss after Day 70 of gestation in a cohort of Thoroughbreds.

Fetal morphological features and abnormalities associated with equine early pregnancy loss.

Background: Early pregnancy loss (EPL) occurs in approximately 8% of equine pregnancies, although the aetiology is mostly unknown and embryonic/fetal morphological abnormalities associated with EPL are not defined.

Objectives: To compare the morphology of EPL to clinically normal embryos/fetuses and previously described embryonic/fetal developmental milestones. To identify morphological abnormalities associated with equine EPL.

Whole genome analysis reveals aneuploidies in early pregnancy loss in the horse.

The first 8 weeks of pregnancy is a critical time, with the majority of pregnancy losses occurring during this period. Abnormal chromosome number (aneuploidy) is a common finding in human miscarriage, yet is rarely reported in domestic animals. Equine early pregnancy loss (EPL) has no diagnosis in over 80% of cases.

Efficacy of ovulation synchronization with timed artificial insemination in treatment of follicular cysts in dairy cows.

The efficacy of five ovulation-synchronization protocols with FTAI in treatment of cows diagnosed with follicular cysts was investigated in a nonrandomized study in a single herd. Cows identified with follicular structures >25 mm on two subsequent ultrasonographic (USG) examinations 7-10 days apart (n = 552) were assigned to one of the five treatment regimens on the day of the second USG examination. Treatment regimens were Ovsynch (GnRH-7d-PGF2α-56 h-GnRH-16 h-FTAI), New-CIDR (as Ovsynch with a new CIDR insert being fitted between days 0 and 7), Reused-CIDR (as New-CIDR but the CIDR insert was previously used for 7 days in another cow), G-New CIDR (Pre-GnRH on day 0 with the New-CIDR regimen being initiated 7 days later), and RG-Ovsynch (Pre-GnRH on day 0 and then every 7 days until detection of a luteal structure upon USG examination; at that point the Ovsynch was initiated).

Dynamic changes in gene expression and signalling during trophoblast development in the horse.

Equine chorionic girdle trophoblast cells play important endocrine and immune functions critical in supporting pregnancy. Very little is known about the genes and pathways that regulate chorionic girdle trophoblast development. Our aim was to identify genes and signalling pathways active in vivo in equine chorionic girdle trophoblast within a critical 7-days window.