Liz O’Flynn discusses how to recognise and prevent dehydration
Part 2: Diagnosis and
Prevention of Dehydration in
Performance Horses
PART 1 of this discussion outlined some of the main problems which may be encountered in horses worked hard in hot and/or humid weather. Dehydration was discussed in some detail.
Part 2 focuses on dehydration diagnosis and prevention in performance horses working under very hot humid conditions.
It should be noted that while extremes in dehydration - associated problems are far more likely to occur in hot climates, they can also occur under cooler conditions from protracted over - exertion /prolonged sessions of heavy work.
A horse with even the mildest form of dehydration may not perform to its full capacity.
It is also important that trainers, owners and riders should be aware that a dehydrated horse may not necessarily show any obvious outward signs.
How is dehydration confirmed?
A blood analysis will readily confirm dehydration in a horse.The following tests can help to ascertain the level of dehydration of a horse:
a) Skin pinch test: Pinch a fold of skin on its neck and observe how quickly the fold returns (flattens on the neck again). In a well hydrated horse, the skin fold will return in a second. If it takes several seconds, the horse is dehydrated. When a horse has 2% level of fluid loss, he will have a slow skin pinch return and may also have a dull dry coat. However, this test can be confusing and inaccurate, particularly as the elasticity of skin varies. The horse’s performance may be affected below the level that a skin pinch test would detect, so it cannot be relied on without assessing other signs.b) Slow Capillary Refill: This is a good indicator for checking more severe dehydration: 2-5% fluid loss – slow capillary refill - when gums are pressed with a Finger, the spot will turn white. In a normal horse, the colour returns within 2 – 3 seconds after removing this pressure. In a stressed dehydrated horse, the spot will stay pale for longer. The more dehydrated the horse, the slower the capillary refill time.c) Other clinical signs as severity of dehydration increases may include :With 5-7% fluid loss – tucked up belly. Urine is darker and thicker. Horse will urinate less or may not pass any urine.Mucous membranes will appear red and congested which is a sure sign of dehydration.With 7-10% fluid loss – sunken eye, small hard pebbly dung.The sweat becomes thicker and more lathered, similar to that of a soft unfit horse.Other clues in severe cases include a weak, fast pulse, sunken eyes and cool extremities. It may not always be that obvious that there is a problem, especially as dehydrated horses have been shown to sweat less than normal animals.Severe dehydration can also trigger muscle cramps (typing up or colic) since fluid and electrolytes necessary for proper muscle function are depleted.In a case where there is 10% plus fluid loss, there will be weakness, fatigue, cold extremities/limbs, collapse if exercised.How is dehydration prevented under these conditions?
Prevention includes basic factors such as:
General fitness maintenanceConditioning of the horse.Clipping of horses in hot climatesProvision of balanced electrolyte supplements as a part of regular nutrition. Salt or sodium chloride is one of the main electrolytes which must be maintained in an appropriate balance.Provision of adequate water frequently.Frequently cooling the performance horse with water to reduce the need for sweating. However, it is important to avoid rapid cooling large muscle areas.Where a horse is reluctant to drink it may be advised to use haylage or wetting the hay may help to increase moisture control.Placing a pinch of salt on the horse’s tongue occasionally may also encourage drinking more water as it makes the horse thirsty.What is the emergency treatment used for a horse showing signs of severe dehydration?
Move the horse immediately into shade. Cool the animal with a fan if possible. Cool also with cool water, again avoiding large muscle areas. For milder dehydration, oral electrolytes or water may be given.For serious cases veterinary treatment and advice should be sought immediately.What is the treatment for dehydration?
The veterinary surgeon may first carry out blood tests to determine specifically which electrolytes are deficient.A severely dehydrated horse will need intravenous fluids monitoring.Fluids via stomach tube can also be helpful but severe and dangerous dehydration can best be reversed by giving electrolyte fluid intravenously. A key point is ensuring that the horse has access to adequate water after administration of electrolytes. It is important not to give electrolytes (e.g. powdered electrolytes) to a horse that is already dehydrated without ensuring that he has had adequate water. A high concentration of electrolytes in the gut may actually pull water from the blood, increasing the dehydration of the body.Approximately four gallons of water should be given before or after the dose. Alternatively the electrolytes may be given in the water if the horse will drink it.Moderate dehydration can be reversed by giving the horse all the water he will drink and allowing him some free-choice salt or electrolyte powder with his feed or dissolved in his water.Intravenous electrolytes may be administered along with other drugs, depending on the treating veterinary surgeon’s diagnosis.Ad lib water supply should always be in place.Some owners are apprehensive about watering a hot horse after exercise but these horses are better off if allowed to drink whenever they want provided it is given in small quantities.The danger in watering a hot horse is when he is allowed to fill up on very cold water and then must stand idle. In this situation, the horse may colic or get muscle cramps.Some horses are more prone to dehydration than others. Higher levels of awareness and extra caution is important in these more susceptible horses, to avoid recurrence.