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Sunday 4 December 2016

Sometimes even horses just don't like Mondays

How to identify and deal with a condition that can strike with little or no warning

Published 01/03/2011 | 05:00

The appearance of equine rhabdomyolosis in draught horses after a weekend earned it the nickname 'Monday morning disease'
The appearance of equine rhabdomyolosis in draught horses after a weekend earned it the nickname 'Monday morning disease'
Draught horses and hunters are equally susceptible to equine rhabdomyolosis. The condition can have a wide range of causes, and its symptoms mean it is often confused with colic, leading to delays in getting the correct treatment
Draught horses and hunters are equally susceptible to equine rhabdomyolosis. The condition can have a wide range of causes, and its symptoms mean it is often confused with colic, leading to delays in getting the correct treatment
Draught horses and hunters are equally susceptible to equine rhabdomyolosis. The condition can have a wide range of causes, and its symptoms mean it is often confused with colic, leading to delays in getting the correct treatment

Monday morning disease -- it sounds like an excuse to ring the boss for a day off work after a weekend on a bar stool but, instead, it's a painful muscle problem that affects horses and requires immediate treatment.

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The condition is known by several names, including azoturia, equine rhabdomyolosis, tying up and setfast, and the symptoms can range from a mild stiffness and cramping to more severe cases where the horse will be unable to stand and will pass red urine.

The name Monday morning disease was used because the condition often affected draught horses on Monday morning -- the morning after their traditional day off.

Rhabdomyolosis means disintegration of striated muscle fibres, with excretion of the pigment myoglobin from the damaged muscle, causing the urine to become a dark red-brown colour.

There are several explanations of the name azoturia. Some say that it is derived from "azo", the red clothing dye, and "uria", referring to urine, while others say that it is a combination of "azote", the Greek word for nitrogen and "uria" for urine.

Other names, such as setfast and tying up, simply describe the effect of the condition on the horse. The horse will appear to be stuck in one spot, unable to move, and as if his hindquarters are tied to something.

In the past, it was also known as market day disease, when it occurred in cobs that were harnessed to carts to go to the market on their only real day of work in the week, and snow/frost disease was the term that was given to hunting horses that tied up after their first day out following an enforced layoff through bad weather.

The symptoms of Monday morning disease or equine rhabdomyolosis (ER) vary widely and are dependant on the individual horse and the muscle damage incurred.

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They include:

  • Hind leg stride becoming shorter
  • Stiffness
  • Sweating
  • Increased pulse rate
  • Muscles hard and painful when pressed
  • Pawing at the ground
  • Reluctance to move
  • Shaking
  • Discoloured (red) urine
  • Turning of the head frequently to look at flanks
  • Laboured breathing

You will notice that some of these symptoms are every similar to those of colic, explaining why vets are often called out to a case of colic only to find that the horse is suffering from ER.

Mild cases of ER begin with the horse becoming stiff, especially over the loins and hind quarters. The muscles will be painful to touch and the horse may have a high temperature and sweat.

As mentioned previously, in severe cases the myogolobin released from the damaged muscles turns the urine dark red and the horse may go down, unable to move.

There appears to be some link between ER and sex, because although the condition can affect a horse of any age, it is much more common in fillies and mares than geldings and stallions.

In fact, Irish racehorse trainers pinpoint young fillies, particularly those with nervous and flighty temperaments, as the category that suffers most often from tying up.

So what causes ER?

Vets on Equinehospital.net, an equine veterinary specialist website, say the predisposing and triggering factor(s) are slightly different for each animal, but they include:

  • Carbohydrate overload

The classic presentation is the draught horse in work that is rested for the weekend on full feed. Then, when the horse returns to work several days later, it suffers an attack of the disease.

It is thought that muscle glycogen accumulates during the rest period and when used during exercise it produces excessive lactic acid. This causes local tissue damage and constriction of the blood vessels, resulting in decreased blood flow to the tissues and further reduction in lactic acid removal.

  • Local hypoxia

Certain types of muscle fibres are larger and have greater glycogen stores and fewer surrounding blood vessels than others. Local hypoxia (lack of oxygen supplied by the blood) may increase the lactic acid production in these fibres. However, ER normally occurs at the start of exercise, when these fibres would not yet be working, and the condition is not usually seen in horses with other conditions causing impaired circulation.

  • Thiamine deficiency

Thiamine (one of the B group of vitamins) acts in the metabolism of waste products from muscle activity. A deficiency, therefore, could lead to a build-up of these waste products and hence lactic acid.

  • Vitamin E and Selenium deficiency

This theory is based on reports of success at preventing further episodes following supplementation, but clinical trials have failed to confirm this.

  • Hormonal disturbances

Reproductive hormones, thyroid hormones and cortisol have all been implicated in ER, but there is still considerable debate.

  • Electrolyte imbalances

Studies from British racing stables have indicated that chronic sodium and/or potassium deficiencies may be involved in chronic ER. This is difficult to detect routinely so a special urine test is used to assess levels.

  • Viral causes

Muscle involvement following viral disease such as influenza has been investigated but the associated muscle pain (myalgia) is generally considered to be a separate and distinct disease process.

However, the causes of ER are so wide-ranging and individual to each horse, its environment and management, that only your own vet could assess the cause of any one case.

So what should you do if your horse shows any of the signs of tying up?

  • Immediately stop work and do not make the horse walk on, as this will make him work the problematic muscles and could worsen his condition.
  • If possible, cover its loins and hind quarters with a rug to keep it warm and prevent chill.
  • Call your vet and if your horse is showing severe symptoms, get the vet to come to where you are. If the symptoms are mild, bring the horse to the nearest stable by horsebox, remembering to drive slowly as the horse will have limited mobility and could struggle to stand while travelling.

While you wait for the vet, offer the horse plain water or pulled grass but not concentrates or electrolytes. Keep the animal well rugged, especially if it is sweating.

Treatment

In his treatment, the vet will be aiming to ease the pain and muscle tension, alleviate the horse's anxiety, limit further muscle damage and, if needed, rehydrate the horse.

Fluid therapy is usually given orally in mild cases and intravenously in severe cases.

The vet may use non-steroidal anti-inflammatory drugs, such as bute, on both mild and severe attacks as pain relief, while steroids might be given during acute stages of a severe attack of ER.

Other drugs to control muscle spasm and help blood flood could also be given.

Recovery

Horses who suffer mild attacks of ER generally recover gradually over the following three to four days.

Vets usually prescribe box rest, followed by a gradual return to exercise.

In some cases, walking the horse out in hand or short turnout periods in a small paddock might be recommended.

Severe cases will take longer to recover and will need to be monitored to make sure their muscle enzyme levels return to normal.

Prevention

Because ER has so many possible causes and triggers, it is a good idea to assess the overall management of a horse that has suffered an attack.

Close attention should be paid to the horse's diet.

Make sure that it is not being overfed for the amount of work it is doing and if it has a day off work, cut back on the concentrate feeding level and make sure to have a long, slow warm-up the next time the animal is ridden.

For some horses, a switch from a high starch and cereals diet to a fibre and oil diet could be the solution.

If antioxidant supply to the muscle is the problem, check that selenium and vitamin E levels are correct in the diet.

If temperament and anxiety are a factor, consider changing the horse's environment to a quieter yard or increasing the amount of turnout.

The bottom line in preventing ER is to ensure a balanced and controlled feeding and exercise regime.

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