Do horses really need electrolytes?

gradually depletes the water volume of blood. In response along with increasing heart and breathing rate the horse reduces blood flow to organs such as the gut. This shunts blood towards essential structures like the muscles. The extent to which the horse must increase its heart rate breathing rate and shunt blood affects the rate at which it recovers from exercise. So the horse that was well hydrated beforehand meaning it had an optimal circulating blood volume and normal intra and extracellular water proportions will recover faster than a dehydrated horse. This highlights the importance of keeping a competition horse well hydrated at all times But especially during warmer months intense competitions and warm climates. 
If the horse was dehydrated to begin with this can have serious implications because the water in the extracellular fluid will be depleted and water in the intracellular fluid may move out to replace it. If cells lose their water to the extracellular fluid they become too dehydrated to work. 
Sweat isnt just water sodium chloride potassium as well as magnesium calcium and some protein all move with the water to the skin surface and are lost through sweating. Combined with consumption of electrolytes by the muscles and other tissues during exercise the result is gradual electrolyte depletion. 
What does this mean for the horse?  
The horse maintains its water and electrolyte balance by eating and drinking. Many horses will be keen to drink during and after competition but water alone wont provide the electrolytes they need to replace. In order to supply these in a timely manner the horse can be fed or syringed electrolyte formulations which will help restore the balance. Every effort should be made to tempt horses who are reluctant to drink during competitions. Otherwise dehydration and electrolyte depletion can lead to serious consequences such as neurological signs and the expected exhaustion dehydration and poor performance.
Its important to recognise that whilst a salt lick can be offered to help with daytoday regulation of the electrolyte balance in any horse giving replacement electrolyte supplements in every meal or before exercise in a normal hydrated horse is generally not necessary. This is because when the balance is right any additional electrolytes will just be excreted and lost in the urine. The time for administering these to performance horses is generally after exercise. This allows replenishment in the period of recovery and when water
and salt losses are replaced.
A word on the Thumps
Otherwise known as synchronous diaphragmatic flutter SDF depleted electrolyte levels are the cause of this odd phenomenon. In a horse that has the thumps the diaphragm contracts in time to the heartbeat because electrolyte abnormalities cause altered activity in the nervous supply to the diaphragm. Some horses might need calcium