Multivariable analysis to determine risk factors associated with early pregnancy loss in thoroughbred broodmares.

Early pregnancy loss (EPL) between days 15-65 after breeding has been shown to occur in 7.9% of equine pregnancies with substantial economical, welfare and safety implications. Whilst maternal age has been recognised as an important risk factor in relation to the incidence of EPL, few other risk factors have been conclusively identified. Further, multivariable data analysis of risk factors for EPL is sparse. A prospective cohort investigation of thoroughbred broodmares in the United Kingdom was conducted over the 2013 and 2014 breeding seasons. Information relating to 28 factors including mare, stallion, pregnancy and therapeutic interventions was collected using questionnaires and entered into a custom-designed Microsoft Access database. Mixed effects logistic regression was used to determine risk factors for EPL, including 'mare' as a random effect to account for repeat pregnancies in the same mare. Stallion, stud and veterinarian were also evaluated as random effects. Variables with a p-value of <0.25 in univariable analysis were taken forward for consideration in the multivariable model which was built using a forward stepwise approach. Data were collected on 2245 pregnancies in 1753 mares. Increasing mare age (OR = 1.11, 95% confidence interval (CI) = 1.04, 1.18, p = 0.001), having had one previous foal (OR = 3.52, 95% CI = 1.56, 7.95, p = 0.002) and presence of uterine cysts (OR = 1.76, 95% CI = 1.07, 2.91, p = 0.03) were all associated with increased odds of EPL following multivariable analysis. Increasing day 15/16 scan vesicle size (OR = 0.24, 95% CI = 0.16, 0.38, p < 0.001) and the use of ovulatory induction agents (OR = 0.31, 95% CI = 0.17, 0.55, p < 0.001) were negatively associated with EPL. Stallion, stud and veterinarian were not significantly associated with EPL. Analysis of a subpopulation of 344 multiple (twin and triplet) pregnancies found that the use of flunixin meglumine at the time of manual reduction of a multiple pregnancy resulted in reduced odds of EPL (OR = 0.34, 95% CI = 0.14, 0.84, p = 0.02). Results from this study can be used by stud farm personnel when assessing their broodmare population and by clinicians when deciding upon therapeutic strategies. Additional work can be focused around these risk factors to further our understanding of the pathophysiology of EPL.

Descriptive study of current therapeutic practices, clinical reproductive findings and incidence of pregnancy loss in intensively managed thoroughbred mares.

Therapeutic practices in equine reproductive medicine have dramatically evolved over the last 20 years but current usage is not described. The aims of this study were to provide a description of medication use and clinical findings of reproductive examinations alongside measures of reproductive efficiency in thoroughbreds. A prospective cohort study was conducted in the 2013 and 2014 breeding seasons. Mare and stallion details, information on veterinary interventions and findings of reproductive ultrasound scans were collected using questionnaires and entered into a custom-designed Microsoft Access database. Descriptive summary statistics were derived directly from the database and using Microsoft Excel. Information was collected from 2246 pregnancies in 1754 mares from 29 stud farms. Ovulatory induction agents were used in 91.8% of cases, oestrus induction agents in 38.4% and covering therapies in 62.7%. Intrauterine antimicrobials were used in 49.6% of mares. Single pregnancies accounted for 83.9% of pregnancies, twins for 15.3% and triplets for 0.7%. The overall incidence of pregnancy loss between days 15-42 was 6.4% (95% CI 5.4%, 7.4%) and 1.6% (95% CI 1.1%, 2.1%) between days 43-65. A further 1.3% of pregnancies were lost by October and 4.5% by birth (including stillbirths). Eighty-three percent of all pregnancies resulted in a live foal. In conclusion, there has been a considerable increase in the use of reproductive therapeutics over the last 12 years. Nonetheless, incidence of pregnancy loss and live foal percentages remain essentially unchanged. Risk factor studies are required to determine if the substantial increase in therapeutic usage is conferring positive benefits.

A method for isolating and culturing placental cells from failed early equine pregnancies.

Early pregnancy loss occurs in 6-10% of equine pregnancies making it the main cause of reproductive wastage. Despite this, reasons for the losses are known in only 16% of cases. Lack of viable conceptus material has inhibited investigations of many potential genetic and pathological causes. We present a method for isolating and culturing placental cells from failed early equine pregnancies. Trophoblast cells from 18/30 (60%) failed equine pregnancies of gestational ages 14-65 days were successfully cultured in three different media, with the greatest growth achieved for cells cultured in AmnioChrome™ Plus. Genomic DNA of a suitable quality for molecular assays was also isolated from 29/30 of these cases. This method will enable future investigations determining pathologies causing EPL.