All Tie-Up? Managing Typing Up in Performance Horses

All Tie-Up? Managing Typing Up in Performance Horses
5 July 2017 | Foran Equine

 

Tying-up is a process whereby the striated muscles, which connect to the bone and allow movement, suffer breakdown following exercise.

Exertional rhabdomyolysis (ER), also known as azoturia, tying up or set fast, is a process whereby the striated muscles, which connect to the bone and allow movement, suffer breakdown following exercise. Incidences of tying up can range from mild muscular stiffness to the muscles becoming locked and the horse unable to move.

ER can be divided into two categories, Acute Exertional Rhabdomyolysis (AER) and Recurrent Exertional Rhabdomyolysis (RER). With AER the horse in question would have a history of previously satisfactory performance, and is most commonly caused by strenuous exercise above the horses’ current level of training. RER can be seen intermittently, sometimes after only mild exercise. Of these two conditions RER is the most frustrating for the rider and is an area in which more research is still needed to determine the exact causes.

Factors leading to tying up in performance horses

Acute Exertional Rhabdomyolysis and Recurrent Exertional Rhabdomyolysis have slightly different effects on the body. More work (research) is needed to fully understand what happens at a muscular level, particularly with Recurrent Exertional Rhabdomyolysis. At the moment the causes can be summarized for each as follows:

Acute Exerctional Rhabdomyolysis

The main cause is depletion of Adenosine Tri Phosphate (ATP), the muscle’s energy source. ATP levels drop when there is marked lactic acid production following speed work. Levels can also drop if glycogen, another muscle fuel, is depleted following endurance work.

Depleted ATP sources and a low muscle pH cause changes at a cellular level in the muscle. These changes include damage to cell membrane/cell structure and damage to the myofibrils which are small fibres that make up muscle tissue.

Recurrent Exertional Rhabdomyolysis

The main cause of RER is less clear and damage can be caused even with light work. It appears to be an abnormality in how the cells regulate calcium, resulting in excess levels of calcium being excreted from the cell body. This causes contractions and muscle spasms.

Recurrent exertional Rhabdomyolysis is linked with several triggers including genetics, high starch diets, management and stress. Research from the USA shows Recurrent exertional Rhabdomyolysis to be more prevalent in mares, with up to 80% of 2 year old fillies being affected. Nervous temperaments will increase prevalence by fivefold and a horse with an underlying lameness is four times as likely to suffer from RER.

Practical management of horses prone to tying up

Dietary changes and specific training programs will help reduce episodes. There is no one magic cure, the best results are achieved when both dietary and management changes are used together.

Dietary changes for horses prone to tying up

Low starch, high fibre and high fat diets are linked with lower incidences of RER in horses. Lower starch diets provide the muscle with alternative sources of fuel and can also help from a stress point of view, as such diets can lower excitability and nervousness.

On days of light work or rest feed levels should be reduced, but not forage intake. This is to cater for possible carbohydrate storage issues in the muscle. Maintaining forage intake is important for stomach and gut health and can also help reduce stress levels for stabled horses.

Vitamin E and selenium deficiency can cause AER, but most horses with RER do not show a deficiency. Vitamin E and selenium are natural antioxidants which are beneficial to muscle health and should be part of any good complete feed.

Daily electrolyte supplementation has been reported to lower incidences. Supplementing with 30 – 45 grams sodium chloride (salt) has been successful in lowering incidences for some horses. Similar studies have shown that supplementing with 11 – 33 grams of calcium daily may be of benefit to prevent tying up in horses.

Including supplements to boost natural reserves of bicarbonate for neutralising lactic acid is also beneficial. This can be done as a preventative measure when working or competing horses and as a daily supplement when managing horses prone to tying up.

Management changes

Some reports suggest lower incidence levels associated with daily work programs for horses with Recurrenct Exertional Rhabdomyolysis. A regular exercise program to steadily build fitness will be of benefit to any horse, particularly in avoiding AER. Turn out to pasture will also be of benefit for stress reduction and increasing forage intake.

In summary, tying up in horses, whether AER or RER, is best managed by a combination of stress reduction, regular exercise, turnout and dietary changes.

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