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Understanding essential electrolytes

Louise Jones MSc, BSc (Hons)

30 June, 2004

Electrolytes are minerals dissolved in the blood and tissues of the body, which carry a positive or negative charge and can bind with another ion to make a "salt". They help to preserve the correct balance of fluids in the body's cells and are involved in muscle function and the processing of wastes. Deficiencies cause dehydration, impaired performance and may exacerbate clinical problems such as azoturia.

The main electrolytes are:

• Sodium (Na)

• Chloride (Cl)

• Potassium (K)

• Magnesium (Mg)

• Calcium (Ca)

Electrolytes are lost daily through sweating, in urine and faeces. These losses can normally be replaced in the diet. The horse relies on sweating to control body temperature during exercise and it is generally accepted that 90% of a horse's weight loss after exercise is due to sweating. It is important that this weight loss is monitored and the fluid and electrolyte losses replaced, otherwise poor performance will result.

During periods of exertion such as competition and training, electrolyte losses can be considerable, particularly during hot weather. Even under normal exercise conditions, a 500kg horse could lose 10 litres of sweat during two hours of exercise. This sweat would contain 60g of Chloride, which represents 10% of the total Chloride in the body.

Signs of electrolyte deficiency include:

• Dull coat

• Sunken eyes

• Depression

• Listlessness

• Poor performance

• Dark urine

Providing electrolytes

The horse's body cannot retain water without the presence of electrolytes, so simply offering water after exercise will not rehydrate your horse. Electrolytes should be added to either the water or the feed.

Adding electrolytes to water to form an isotonic solution (a solution that contain the same electrolyte concentrations as that of the body fluids) will ensure that both fluid and electrolyte losses are replenished and the horse becomes quickly rehydrated. However, after prolonged sweating it will take several days of electrolyte supplementation to completely replenish losses.

Alternatively, if your horse is a poor drinker or there is no opportunity to replace fluid losses during the competition, electrolytes may be fed alongside a small amount of concentrate feed. Electrolyte pastes are also available. However, a large single dose can cause the horse to absorb water from the blood vessels surrounding the gut and actually worsen the effects of dehydration in the short term.

Sodium chloride (salt) should be available for the horse ad lib in the form of a salt block and intake should be monitored, particularly in hot weather. Alternatively feeding a tablespoon of table salt daily will ensure you horse receives sufficient sodium chloride.

Avoiding dehydration

• Feed a diet formulated to meet the nutritional requirements of your horse

• Add electrolytes to the morning feed particularly in hot weather, before a competition or long journey

• Always allow free access to water

• Allow your horse to consume some hay 4-5hr prior to exercise as this will improve water retention

• After a competition offer water followed by a little hay

• Add a little water to the concentrate feed or feed sloppy sugar beet to improve water intake

• Feed haylage rather than hay as it contains more water, although to meet fibre requirements you will need to feed larger quantities compared with hay

Dodson & Horrell's top tip

"Horses who refuse to drink at competitions or dislike the taste of an isotonic electrolyte supplement, can be encouraged by flavouring your water at home with apple squash. This will mask any unfamiliar or unpleasant tastes and will help encourage your horse to drink while away from home," says Dodson & Horrell nutritionist Louise Jones.

Feeding Electrolytes Dodson & Horrell's wide range of supplements includes Surelyte, a comprehensive blend of electrolyte salts that can be added to feed or water. For further information and friendly feeding advice call the Dodson & Horrell Feed Helpline (tel: 0870 442 3322) Normal national call rates apply, or visit: www.dodsonandhorrell.com

Related articles:

• Ask H&H: dampening feed
• Avoiding dehydration
• The importance of water
• Replacing electrolytes
• Tricks of the trade: watering
• Understanding the effects of dehydration
• Keeping your horse hydrated
• Understanding water
• Q&A: Drinking from troughs
• The importance of water quality

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