Heat
and the
Exhausted Horse Part one
Heat
and the Exhausted Horse Part Two
Prevention and
Treatment
During exercise, food, water and oxygen is metabolised as fuel to feed individual cells and clear the waste products. Most waste is eliminated through the kidneys and large amounts of heat are produced when glycogen is oxygenated to produce energy.
The blood becomes hot and the circulation to the skin is increased, consequently surface veins dilate so that more hot blood is brought to the surface for heat exchange. If there is too much circulation to the skin, there can be a deprivation of the circulation to muscles and vital organs, the gut included.
A poorly perfused gut causes the muscle in the gut wall to become static and normal peristaltic contractions reduce or cease. This is called "ILEUS" and can be very painful for the horse, especially when the circulation to the gut returns, and cramps or colic occur.
Constant monitoring of gut sounds is a way of checking gut mobility and ultimately gut perfusion. If a horse has become dehydrated, there is less circulating fluid available to supply the demand of heat dispersion, metabolism, muscle function and gut mobility. Inevitably the gut will loose out and sweating is reduced, the horse becomes hotter with more work and will suffer heat stress or exhaustion.
A horse can be conditioned in its fitness program to increase the aerobic threshold, lower the heart rate and reduce heat production.
Horse that undertake
strenuous exercise are often pushed to their limits, past their thermoregulatory,
metabolic and cardiovascular mechanisms and homeostasis is indequate. A shock
line state occurs with exhaustion.
Risk
factors for development of exhaustion include:-
Hot, humid
conditions
Poor fitness
High altitude
Rough or steep terrain
Rider inexperience
Antidrosis (lack of sweating)
Concurrent disease or lameness
Signs
of shock are evident as:-
Hyperthermia (increased
body temperature)
Depression
Weakness
Tachycardia (high heart rate)
Tachypnea (high respitory rate)
Delayed capillary refill time
Dry mucous membranes
weak peripheral pulses.
Multiple
organ dysfunctions include a combination of:-
Myopaphy
Renal Failure
Ileus
Coagulopathy (clotting defects)
Central
nervous system derangement sometimes in early cases is manifisted by slightly
unusal errattic behavour.
Without veterinary attention these horse may die.
