title: Diagnosis and epidemiology of Equine Metabolic Syndrome in native ponies and cobs in the UK
Creators: name: Carslake, Harry
Publisher: name: University of Liverpool Repository
Year: 2022

description: Equine metabolic syndrome (EMS) is a collection of risk factors for endocrinopathic laminitis, a painful condition of the feet which has a significant impact on the welfare of horses. The central and consistent feature of EMS is insulin dysregulation (ID), leading to hyperinsulinaemia. As a result, the diagnosis of EMS focuses on detection of ID and its associated risk factors. Laboratory testing for EMS commonly involves measurement of insulin concentration, but immediate analysis is rarely available in clinical practice. In a cross-over study the storage of whole blood at room temperature had a clinically insignificant effect on insulin concentration compared to immediate separation and freezing. This supports the practice of posting whole blood tubes to laboratories. At most commercial laboratories a chemiluminescent assay (CLIA) is used for measurement of insulin concentration, whereas early experimental work mostly used a radioimmunoassay (RIA), potentially affecting the translation of experimental data into clinical practice. Evaluation of the CLIA using 78 equine serum samples showed it had very good precision. There was a strong positive correlation between the RIA and CLIA, however at concentrations &lt;100μIU/mL the CLIA results were slightly lower, and results should be interpreted accordingly. Many diagnostic tests for EMS have been described, offering various practical and/or diagnostic advantages. Their accuracy is poorly described, however, and comparison of results problematic. One novel and four established diagnostic tests were compared. There was reasonable agreement between oral dynamic tests, despite the palatability of some feedstuffs being variable. Accuracy compared to a CGIT was adequate. Fasting basal insulin lacked sensitivity. Management of EMS commonly involves feeding preserved forages, with soaking frequently used to reduce non-structural carbohydrate content. In the same cross-over study, soaking hay significantly reduced glycaemic and insulinaemic responses, supporting this practice for management of EMS. Insulin concentration can be substantially affected by forage type, and this should be considered during management. The contribution of the enteroinsular axis (EIA) to ID has received increased interest in recent years. Measurement of the main hormone in the EIA, glucagon-like peptide -1 (GLP-1), following forages and oral carbohydrate tests demonstrated a functioning EIA in ponies but no consistent association with EMS status, as defined by conventional tests. The first epidemiological study examining prevalence and risk factors for EMS was performed in 354 ponies and cobs. The prevalence of EMS was 23.3% (95%CI 17.9% – 29.8%), and risk factors identified included obesity, age, breed, a more sedentary main activity and alterations in hoof rings. The results of this thesis will help clinicians and horse owners identify horses with EMS and implement management strategies to reduce the risk of endocrinopathic laminitis.