What is acidosis?
An increase in the hydrogen ion concentration within blood plasma results in what is commonly known as lactic acidosis. Lactic acid buildup can have serious ramifications on both the health and racing performance of a horse.
Mechanisms of action;
When a horse’s aerobic threshold (VO2 max) is exceeded during high intensity exercise (ie; galloping), large electrolyte losses occur (in particular sodium) and the anaerobic pathway of energy metabolism must be utilised. Energy is derived from glycogen stores to fuel muscle contractions (anaerobic glycolysis) which results in the production of waste material in the form of lactic acid. A combination of excessive electrolyte losses and increased blood acidity (decrease in blood pH) contribute to muscle fatigue, soreness and stiffness during intense exercise
How can the incidence and severity of lactic acidosis be minimised?
Conversely, what is alkalosis?
A decrease in the hydrogen ion concentration within blood plasma results in what is commonly known as alkalosis. Similarly to acidosis, alkalosis can also have serious ramifications on the health and racing performance of a horse.
Mechanisms of action;
Horses which are involved in prolonged, sub-maximal exercise (ie; trotting/pacing) will experience large amounts of sweat loss and a subsequent increase in blood alkalinity (increase in blood pH). Sweat loss during sub-maximal exercise is associated with a significant reduction in chloride, potassium, calcium and magnesium ions. This results in an increase in plasma bicarbonate and blood alkalinity (alkalosis). Alkalosis may cause altered neuromuscular transmission, cardiac arrhythmias, gastro-intestinal disturbances, muscle cramps and diagrammatic flutters (‘thumps’). Alkalosis may also impact on a horse’s VO2 max, therefore increasing the reliance on muscle glycogen to fuel muscle contractions.
Thumps is a result of excessive calcium losses via sweat and inadequate mobilisation of bone calcium stores.
How can the incidence and severity of alkalosis be minimised?
–A.R PÖsÖ Monocarboxylate transporters and lactate metabolism in equine athletes: A review. ACTA Veterinaria Scandinavia 43 pp.63-74 (2002)
-Assenza, A., Caola, G., Fazio, F., Percipalle, M., Piccione, G. Assessment of anaerobic threshold in the galloper using a standardized exercise field test. Veterinari Medicina 49 pp. 291-297 (2004)
-Matsui, A . et al. Estimation of total sweating rate and mineral loss through sweat during exercise in 2-years old horses at cool ambient temperature, Journal of Equine Science 13 pp. 109-112 (2002).