Cardiovascular, acid-base, electrolyte, and plasma volume changes in ponies developing alimentary laminitis

Area of Science:

• Equine medicine
• Animal physiology
• Veterinary pathology

Background:

• High-starch rations are common in equine diets.
• Laminitis is a significant cause of morbidity in horses.
• Metabolic disturbances can precede or accompany laminitis.

Purpose of the Study:

• To investigate the physiological and metabolic changes associated with high-starch-induced laminitis in Shetland ponies.
• To identify potential predictors for the onset of laminitis.
• To characterize the cardiovascular and acid-base status during and after overfeeding.

Main Methods:

• Twelve Shetland ponies were fed a high-starch ration.
• Physiological parameters (heart rate, blood pressure, cardiac output) and blood values (serum electrolytes, hematocrit, plasma volume) were monitored.
• Acid-base status (metabolic acidosis) and body temperature were assessed.

Main Results:

• Seven ponies developed laminitis 56 hours post-overfeeding, preceded by hypokalemia, hyperthermia, and increased heart rate.
• Cardiovascular changes (increased cardiac output and blood pressure) were observed at laminitis onset.
• Three ponies died from shock, exhibiting severe metabolic acidosis and altered hemodynamics.
• No measured parameters reliably predicted laminitis onset.

Conclusions:

• High-starch overfeeding can induce laminitis and shock in Shetland ponies.
• Metabolic acidosis and persistent hypokalemia are key features.
• Hypertension is likely a response to laminitis, not a cause.
• Predictive markers for laminitis onset remain elusive in this model.