Why do racehorses sweat?
When a racehorse runs, it converts food into energy to power its muscles. This metabolic conversion creates heat, which
is released by sweating. By a process of evaporative cooling, most of the heat is released from the skin to the air via the
sweat glands. The rest is dispersed via the horse’s lungs.
Racehorses may start to sweat before the race. If the weather is hot, it’s not unusual for a horse to sweat up in the
paddock. Unless the sweating is excessive, this shouldn’t be regarded as a bad sign.
Racehorses may also sweat up due to activation of the sympathetic nervous system. Unless it’s their first visit to a
racecourse, they know that they have come to the races to race. This change of daily routine may cause them to be on edge.
If it’s their first time at the track, they may be apprehensive of what lies ahead. When the sympathetic nervous system is
stimulated by apprehension or nervousness, core body temperature rises, which results in sweating.
To perform at its best, a horse must have the correct balance of electrolytes in its body fluids. Electrolytes, such as
sodium and potassium, are substances that conduct an electrical impulse in solution. They are essential for the transmission
of nerve impulses and for muscle contraction. Pre-race sweating can affect the electrolyte balance, adversely affecting the
efficient functioning of muscles and nerves.
Sweating caused by friction of the reins
If a horse is walking calmly around the paddock, its performance is unlikely to be compromised by slight sweating on its
neck, caused by friction of the reins.
Sweating under the saddle
Similarly, there is usually no need to be concerned about a horse that is sweating slightly under the saddle, which is
caused by the saddle cloth rubbing against the back.
Sweating between the back legs
However, slight to moderate sweating between the back legs, on the flanks or over the loins should be taken as a warning
sign that the horse is worrying, especially if it is jig-jogging in the paddock with ears flicking or tail swishing.
Unless it is a very warm day, be very cautious of a horse that has got itself into a lather, sometimes referred to as a
‘muck sweat’. One of the properties of sweat is a protein that acts like a detergent and helps the sweat to evaporate. When
this protein becomes depleted through prolonged or excessive sweating, lather is the result.