Effect of a long-term high-energy diet on cardiovascular parameters in Shetland pony mares.
Authors: D' Fonseca Nicky M M, Beukers Martjin, Wijnberg Inge D, Navas de Solis Cristobal, de Ruijter-Villani Marta, van Doorn David A, Stout Tom A E, Roelfsema Ellen
Journal: Journal of veterinary internal medicine
Summary
Equine metabolic syndrome (EMS) is associated with cardiovascular changes, but the sequence in which these alterations develop remains poorly characterised. D'Fonseca and colleagues investigated this progression by feeding 20 Shetland pony mares a high-energy diet providing 200% of maintenance requirements for one or two consecutive years, interspersed with hay-only periods, whilst monitoring blood pressure via non-invasive measurement, cardiac structure through echocardiography, heart rhythm via 24-hour ECG, and autonomic markers including splenic volume and packed cell volume. After just one year of overfeeding, left ventricular wall thickness increased significantly compared to control animals; by the second year, systolic, diastolic and mean arterial blood pressures had risen substantially alongside elevated resting heart rate and further cardiac hypertrophy, yet no pathological arrhythmias or autonomic dysfunction markers were evident. This sequential pattern—early myocardial thickening progressing to hypertension and tachycardia—clarifies the timeline of cardiovascular remodelling in EMS and has considerable relevance for farriers, vets and physiotherapists managing the growing population of overweight and obese horses, suggesting that modest weight management interventions implemented in the early stages might interrupt this potentially pathological cascade before haemodynamic dysfunction becomes established.
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Practical Takeaways
- •Overfeeding high-energy diets to ponies produces measurable cardiovascular changes within 1-2 years; monitor body condition and caloric intake carefully to prevent metabolic disease progression
- •Blood pressure and cardiac wall thickness changes appear to develop sequentially in equine metabolic syndrome, suggesting early intervention before structural cardiac changes could be beneficial
- •The absence of arrhythmias despite hypertrophy and hypertension indicates subclinical disease may be present—regular cardiovascular assessment is warranted in obese/overfed horses even without clinical signs
Key Findings
- •High-energy diet induced increased relative left ventricular wall thickness in year 1 (P=0.001)
- •After 2 years of high-energy feeding, systolic (P=0.003), diastolic (P<0.001), and mean arterial blood pressure were significantly elevated compared to controls
- •Heart rate significantly increased in high-energy diet mares after 2 years (P<0.001)
- •Progressive cardiac changes occurred in sequence: initial blood pressure changes followed by left-sided cardiac hypertrophy, with no pathological arrhythmias detected