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Tying Up is also known as Monday Morning Disease, Exertional Rhabdomyolysis and Azoturia. These terms are used to describe muscle disorders that result in massive contraction of the muscle groups along the rump and back of the horse.
By Saracen Horse Feeds
May 20, 2005 - 8:07:00 AM
An Introduction to Tying Up in horses & ponies
Tying Up is also known as Monday Morning Disease, Exertional Rhabdomyolysis and Azoturia. These terms are used to describe muscle disorders that result in massive contraction of the muscle groups along the rump and back of the horse. The condition is extremely painful and the horse will sweat and have an elevated respiratory rate. Its onset is usually during or following exercise. In severe cases the horse may pass a dark red/brown urine (myoglobinuria). This decolourisation of the urine is caused by the presence of Myoglobin. Myoglobin is a muscle protein that leaks into the bloodstream as the muscles become damaged. It is transported via the bloodstream to the kidneys where it is excreted in the urine.
The condition was first described in the days when horses worked for a living. Draft horses that were worked all week and then rested on a Sunday without having their grain ration cut back, developed signs of Tying Up on a Monday morning when they returned back to work. Hence the name Monday Morning Disease. Studies in 1932 (Carlstrom, 1932) showed that draft horses given high amounts of non-structural carbohydrates e.g. Molasses were more likely to develop muscle damage with exercise. However the condition is also seen in horses that are of a nervous disposition and in some for what appears to be no reason at all.
A horse that is prone to Tying Up can be sensitive to a number of different things and what triggers an attack in one horse may not necessarily do the same in an other. Learn what factors trigger an attack in your horse and work to minimize them.
SOME PROPOSED CAUSES:
CARBOHYDRATE OVERLOAD:
Soluble carbohydrates are normally digested in the small intestine by enzymes. However the horse evolved to trickle feed on high fibre food sources so the small intestine can very easily become overloaded with carbohydrates. This results in undigested carbohydrates flooding in to the hindgut. The microbes that are present in the hindgut undergo a population explosion as they feed on the starch. One of the products that they produce is lactic acid. This causes a drop in the pH level of the hindgut and creates an environment, which is not suited to the microbes. As a result they begin to die and release endotoxins in to the blood stream. These circulating endotoxins may contribute to Tying Up as well as being the most noted cause of laminitis.
This also causes fluctuations in blood glucose levels and circulating hormone levels e.g. Insulin, as well as increased heat of digestion. Horses that are prone to Tying Up greatly benefit from having the level of starch in their diet reduced and replacing it with highly digestible fibre sources e.g. Sugar Beet, Alfalfa, Soya Hulls etc and oil if higher energy levels or conditioning is required. Research has shown that while there were no significant differences in muscle glycogen or lactate concentrations as a result of feeding fat (MacLeay et al., 1999c) the reduced emphasis of starch in the diet means that excitability in these susceptible horses is reduced.
BALANCED VITAMIN AND MINERAL LEVELS, ESPECIALLY VITAMIN E AND SELENIUM:
During exercise in both humans and equines oxygen free radicals are produced by the body. A free radical is a highly reactive form of oxygen destroying cells within the body. In the process of breaking down (oxidizing) carbon-containing compounds (carbohydrates, protein and fat) for energy, oxygen is used and carbon dioxide and water are produced. When water is formed from oxygen, a highly reactive form of oxygen (free radical) can be produced which, if not destroyed can damage living cells. Antioxidants are present within the body to destroy these free radicals before they damage the cell. Vitamin E and Selenium are examples of two antioxidants.
Athletic horses require large amounts of energy to be able to perform and therefore they produce more free radicals compared to a horse that is doing less work. These horses therefore require a higher level of antioxidants in their diets, which is probably why horses that are prone to Tying Up are seen to benefit from supplementation from vitamin E and Selenium.
ELECTROLYTE IMBALANCES:
Electrolytes are salts that when dissolved in water will dissociate and form ions. Ions have either a positive or negative charge, e.g. Salt or NaCl, will produce a positive ion Na+ and a negative ion Cl-.
Electrolytes are an essential part of all body functions and maintain an electrical gradient across muscle cell membranes. When muscles contract i.e. during exercise, nerve impulses stimulate a change in the chemical gradient and these ions move across the cell membrane.
There are five important electrolytes in the horse and these are: Sodium (Na+), Chloride (Cl-), Potassium (K+), Magnesium (Mg 2+), and Calcium (Ca 2+).
They all have slightly different roles and must be present in specific ratios. Horses can loose large amounts of these electrolytes in their sweat. Horses that are working hard e.g. Endurance Horses can loose up to 10-15 litres of sweat per hour, and because of the important role that electrolytes play in maintaining cell integrity it is imperative that lost electrolytes are replaced to prevent an episode of Tying Up.
INCREASED BODY TEMPERATURE:
Horses that are competing in hot conditions can easily succumb to heat stress and dehydration. The Animal Health Trust advises that these animals should be cooled rapidly by applying cold water to the large working muscles for 20-30 seconds and then the horse should be walked around for 20-30 seconds and the procedure repeated until the horse has properly cooled down. A normal resting rectal temperature should be 37-38ºC.
TEMPERAMENT:
Some horses that are easily stresses or excitable also appear to be susceptible to episodes of Tying Up.
DIAGNOSIS OF TYING UP:
Diagnosis of Tying Up is confirmed by the detection of elevated serum activities of Creatine Kinase (CK) and Aspartate Aminotransferase (AST) in the blood. CK and AST are muscle proteins that are released in to the blood when muscle cells are damaged. CK levels rise quickly when there is muscle damage, whereas AST rises more slowly. The different rates of response and recovery of the two enzymes after an episode of Tying Up means that the recovery of the horse can be monitored by taking serial blood tests. Horses should not return to work until these levels are back to normal resting levels.
MANAGEMENT OF TYING UP:
Horses that are prone to Tying Up should be fed diets that are low in soluble carbohydrates i.e. starch. Diets that are high in digestible fibre are more suitable e.g. Feeds containing Sugar beet, Soya Hulls, Alfalfa etc, and high in fat (if high energy levels are required). Those horses that are in light work can usually be maintained on good quality hay or haylage, high fibre cubes with a good broad-spectrum vitamin and mineral supplement. For those animals in medium to hard work diets such as Re-Leve a diet formulated by the Kentucky Equine Research is specifically formulated to help manage such problems.
Ensure that you are feeding the manufacturers recommended feeding levels to maintain correct trace element levels. Diets that are specifically formulated for the condition contain elevated levels of antioxidants, alternatively discuss with your nutritionist or veterinary surgeon vitamin E and Selenium supplementation.
Add 1-2oz of salt to your horse’s daily feed ration (always ensure that fresh water is available). If your horse sweats a lot and regularly use a good electrolyte supplement immediately and continue using for two to three days following. Some electrolytes e.g. Endura Max from the KER are actually the same composition as equine sweat, which makes them very effective.
Feed plenty of succulent feeds e.g. Sugar Beet if your horse has sweated a lot to prevent dehydration.
For increased energy levels use oil. Oil is digested very effectively primarily in the small intestine and provides slow release energy. Oil helps to maintain steady glucose levels, and reduces blood lactate levels.
Reduce hard feed levels on rest days.
If possible turn your horse out daily or if no turnout is available on ‘rest days’ gently walk out to stretch and loosen up muscles.
Put in to place sensible and progressive exercise and fittening regimes and increase the intensity of exercise as fitness increases.
Before and after work allow for a period of slow warming up and cooling down respectively.
With horses that are easily stressed or excitable take a look at their environment to see if there is anything that could be improved e.g. company, increased turnout time etc. It may also be a good idea to talk to a herbalist company about the benefits of using calming supplements.
Lizzie Drury BSc (Hons)
Nutritionist for Saracen Horse Feeds;
For a free Feedcheck to be done on your horse, to make sure that you are feeding a well balanced diet, please contact Saracen Horse Feeds on: (01892) 863236 or E-Mail us at info@saracen-horse-feeds.co.uk or write to us at Bradleys Mill, Speldhurst, Tunbridge Wells, Kent, TN3 ONG.
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