Background: Overfeeding is associated with obesity and insulin dysregulation (ID), which are both risk factors for equine metabolic syndrome. How chronic overfeeding affects development of these factors is poorly understood.Objectives: To examine the influence of long-term high-energy diet provision on body condition and ID.Animals: Eleven Shetland pony mares. Methods:In a 3-phase study, the high-energy group (n = 7) was fed 200% of net energy (NE) requirements (hay; concentrate: 36% sugar and starch, 13% fat) for 24 weeks, followed by 17 weeks hay-only feeding before resuming the high-energy diet (n = 4) for an additional 29 weeks. Mares were weighed weekly. Oral glucose tolerance tests were performed 3 to 4 times per dietary period. Results were compared with those of a control group (phase 1, n = 4; phases 2 and 3, n = 6) that received 100% NE requirements, using a general linear mixed model with post hoc Bonferroni testing.Results: The mean body weight of the high-energy group increased by 27% per highenergy feeding period. During both feeding periods, area under the curve (AUC) for plasma glucose concentration decreased (P < .01), whereas AUC for plasma insulin concentration increased. Mean basal plasma glucose concentration and peak plasma insulin concentrations were higher (P < .05) in the high-energy group than in the control group.Conclusion and Clinical Importance: Feeding a high-energy diet to healthy nonobese Shetland pony mares led to more efficient glucose metabolism within 5 weeks, followed by significant hyperinsulinemia and obesity. Hyperinsulinemic status was

Background Changes in cardiovascular parameters, including blood pressure (BP) and cardiac anatomical dimensions, are an inconsistent feature of the equine metabolic syndrome. The order in which these changes arise is unknown. Objectives Determine the order in which EMS‐associated changes in cardiovascular parameters arise. Animals Twenty Shetland pony mares. Methods High‐energy (HE) diet mares were fed 200% of net energy requirements for 1 (n = 3) or 2 (n = 7) consecutive diet‐years, with 17 weeks of hay‐only between years. Noninvasive BP measurements and echocardiograms were performed during both years. Resting 24‐hour ECGs and measurements of autonomic tone (splenic volume and packed cell volume [PCV]) were performed at the end of diet‐year 1. Results were compared to control mares receiving a maintenance diet for 1 (n = 7) or 2 (n = 3) consecutive years. Results In year 1, HE mares had significantly higher values than control mares for mean relative left ventricular wall thickness (P = .001). After 2 diet‐years, mean systolic (P = .003), diastolic (P < .001) and mean arterial BP (P = .001), heart rate (HR; P < .001), and mean left ventricular wall thickness (P = .001) also were significantly increased in HE compared to control mares. No pathological arrhythmias or differences in splenic volume or PCV were detected. Conclusions and Clinical Importance Ingesting a HE diet first induced minor changes in BP, and progressed to left‐sided cardiac hypertrophy in Shetland pony mares. These findings are of interest given the increasing incidence of obesity in horses.

Maternal overfeeding is associated with disturbances in early embryonic epigenetic reprogramming, leading to altered expression of imprinted genes and nutrient transporters, which can affect both fetal and placental development and have lasting effects on the health of resulting offspring. To examine how maternal overfeeding affects the equine embryo, Shetland pony mares were fed either a high-energy (HE: 200% of net energy requirements) or maintenance (control) diet. Mares from both groups were inseminated, and day-seven embryos were recovered and transferred to recipients from the same or the alternate group. The expression of a panel of imprinted genes, glucose and amino acid transporters, and DNA methyltransferases (DNMTs) were determined in conceptus membranes after recovery on day 28 of gestation (late pre-implantation phase). The expression of nutrient transporters was also assessed in endometrium recovered from recipient mares immediately after conceptus removal. In addition, glucose uptake by day-28 extra-embryonic membranes, and lipid droplet accumulation in day-seven blastocysts were assessed. Maternal overfeeding resulted in elevated expression of imprinted genes (IGF2, IGF2R, H19, GRB10, PEG10 and SNRPN), DNMTs (DNMT1 and DNMT3B), glucose (SLC2A1), fructose (SLC2A5) and amino acid (SLC7A2) transporters following ET from an HE to a control mare. Expression of amino acid transporters (SLC1A5 and SLC7A1) was also elevated in the endometrium after ET from HE to control. Maternal overfeeding did not affect lipid droplet accumulation in blastocysts, or glucose uptake by day-28 membranes. It remains to be seen whether the alterations in gene expression are maintained throughout gestation and into postnatal life.