Effect of a long‐term high‐energy diet on cardiovascular parameters in Shetland pony mares

Abstract

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.

Investigating the Relationship Between Cardiac Function and Insulin Sensitivity in Horses: A Pilot Study

“…In this study, there was no significant correlation of insulin sensitivity with relative wall thickness (RWT), mean wall thickness (MWT) or left ventricular (LV) mass, which are indices reflective of ventricular remodeling. This is in contrast to studies in ponies with EMS (12,34), which found increases in MWT and RWT without increases in LV mass, indicative of concentric remodeling. In humans, MetS is associated with increased RWT (35,36), indicating concentric remodeling.…”

“…In our study, decreases in insulin sensitivity were not correlated with blood pressure. Studies in ponies have reported hypertension associated with metabolic syndrome (11,12,34), preceding left ventricular hypertrophy (34). The study by Heliczer et al (12) found that in Shetland ponies, but not all ponies, those with EMS had significant increases in systolic and mean arterial blood pressures compared to controls.…”