Veterinary surgeon
Liz O’Flynn gives
essential advice on preventing equine
dehydration
Part 3: Reducing the risk 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 humid weather. Dehydration was discussed in some detail.
Part 2 focused on dehydration diagnosis and its treatment in performance horses working under very hot humid conditions.
How can the risk of Dehydration and Heat Stress be reduced?
The golden rule is to replace fluid and electrolytes at every opportunity. When humans and horses exercise in hot conditions, they will suffer greater fatigue and slower recovery. This is because more body salts (electrolytes) are lost through more sweating.So it is very important to use electrolytes that will help replace all the essential salts that are lost through sweat. However salt and electrolytes should never be given without adequate fluid at the same time.When a horse sweats, it loses sodium chloride, (common salt) as well as body salts (electrolytes – potassium and magnesium). Providing electrolytes after exercise will help considerably. For horses working more than 30 minutes a day in very warm conditions, it has been recommended by some vets to give approximately one tablespoon of salt per 150kg of body weight to replenish sodium and chloride. However it is very important not to overdose with salt as this could cause salt poisoning.Horses in training should also be provided with potassium and magnesium salts in line with the treating vet’s advice.It is advisable to allow frequent small drinks when exercising.It is wrong to withhold water over an extended period before competing. Many tend to withhold water from racehorses for 12 hours pre-racing to prevent a horse bleeding from the nose or a lung bleed. Water and electrolytes are normally replenished by a horse’s normal diet, but there may not be the opportunity to do this in a lengthy competition situation.Water alone will not provide rapid rehydration, as electrolytes particularly sodium, are essential and needed.Offering water without replenishing the lost electrolytes may dilute the body fluids and disturb the electrolyte balance further.To prevent this imbalance, there are a variety of commercially available equine oral replacement solutions. It is important that these are made up at the correct concentration and even more crucial that the horse will take them.Adding electrolytes to drinking water can cause a reduction in water consumption as the horse may dislike the flavor of the product.Adding apple squash or juice can help to mask the taste of salts in water; some use apple sauce to make palatable electrolyte pastes. If horses are trained to this before a competition, they are more likely to take it readily when they need salt supplementation.It is impossible for a horse to store extra electrolytes for future needs, so there is little point in giving extra electrolytes on a regular basis unless a blood analysis indicates that they are required. Under normal conditions, an adult horse on a good diet will receive adequate electrolytes.Horses that sweat excessively may need additional salt added at approximately 1% of the daily ration but only on veterinary advice.It is usually sufficient to give an electrolyte supplement as soon as possible after major exertion that includes sweating.Some request their vet to stomach tube a “saline” into the horse, or to give intravenous fluids 24 hours before racing or major exertion.What other factors are important to reduce the risk of dehydration?
Cooling off post exercise
It is very important to cool off the horse thoroughly as soon as possible after exercise on a hot day to reduce sweat losses. Once the horse stops sweating, it will become less dehydrated. Pre-cooling - if a horse must be worked in hot and or humid conditions
Hosing the horse’s upper body, lower chest and belly area with cold water will help to: Remove ‘skin heat’, saturate the hair coat (as sweat normally would). This helps in cooling the horse while he is moving. As the horse works, the water in the coat will remove heat as it evaporates.In a 30 minute exercise period, this evaporation can reduce the heat load by 10-15%.Shorten the work session
Warming up a horse for 10-15 minutes instead of 30-40 minutes will reduce the load on his cooling system. This adjustment should be gradual and done in line with the type of animal and its broader work programme.Ensure adequate intake of water.
Provide access to plenty of cool clean water at all times. Place containers in shade. Most horses will drink twice as much cool water (-25 degrees C or under), as they will warm water (30 degrees C or more).Clean the water containers frequently, as even low levels of green algal contamination make water unpalatable to horses.Horses can consume up to 40-50 litres of water per day in hot weather.Scrape the horse after hosing
Always scrape off excess water in the coat to improve evaporation.If there is no airflow – i.e. the wet horse is standing still - the heat gets trapped in the water in the coat and acts as a ‘blanket’ and it is unable to evaporate efficiently.Sand roll
Allowing a horse to roll in sand when he is hot helps to redistribute gut heat reserves, and open the hair coat with sand particles to enhance heat shedding – it can increase the evaporative surface up to 100%. A shaded part of a sand arena should be used for this purpose.Wet Cooling Sheet (Wet wicking)
In hot conditions, a ‘wet wick’ cooling sheet may sometimes be used in the stable during the day.A cheap substitute is an old hessian bag cut into a long strip and soaked in water – this can be spread along the horse’s backline from his wither to aid cooling.Maintain Adequate Fitness levels
Fitness helps in combating dehydration. A fit horse is far less likely to suffer from fatigue of the respiratory muscles.A conditioning programme is also very beneficial to the respiratory system. Horse trainers/owners/riders that compete in strenuous athletic events such as dressage, eventing, racing, etc should be familiar with each of their horses’ abilities, recovery rates, conditioning and body needs; awareness of the signs and effects of dehydration, and how to prevent excessive fluid loss, are essential key aspects here.Shade
During summer competitions/events etc, horses should be kept in the shade wherever possible.Some degree of dehydration is inevitable with strenuous performance, but learning to cope with it through proper conditioning in training, will keep the horse healthy and at peak performance levels.