I thought that might get your attention! But what I’m actually referring to is a condition known as “Monday Morning Disease”. Once again I’m not ­referring to the overall apathy that we as humans may feel when we wake up on a ­Monday morning – I’m referring to the equine equivalent.

Monday Morning Disease is manifested as very stiff muscles and a sore, stiff gait. It ­normally occurs on a ­Monday morning because ­horses that are in work, are normally on a high ­carbohydrate diet for ­training purposes, and then after a weekend of rest, a heavy ­workout on the Monday morning is the cause of the problems.

But it does not just occur as a result of these circumstances, and it most certainly does not just occur on Mondays. So for the balance of the article, I’d like to refer to Monday ­Morning Disease by its scientific name – exertional rhabdomyolysis or ER.

The true effects of ER are not just ­temporary, and it can be a pretty serious condition – so ­serious in fact, that it can bring a sporting horse’s career to a premature end. ER can ­either ­occur as a single or infrequent episode, or in the chronic form when repeated episodes can occur with even very light exercise.

ER episodes (not the medical drama!) ­occur frequently among endurance horses, three day eventers and among racing horses. In fact, ER is the most commonly treated metabolic ­condition treated at the Fauresmith endurance ride. The combination of exercise beyond the horse’s ability, a high carbohydrate diet, long periods of transport and stress is the ideal recipe for an ER episode. And because stress plays such a significant role, Thoroughbreds, Quarter horses, Arabians and other highly-strung horses are breeds that are more prone to certain forms of ER.

ER is characterised by muscles tremors and muscles stiffening up, especially the back (lumbar) muscles and the muscles of the rump (gluteus), as well as less ER-specific signs such as sweating, high pulse rate, rapid breathing rate, colic signs, collapse and shock.

Another very important sign is ­brownish-red to coffee-brown discolouration of the urine. This is an indication of severe breakdown of muscles, or more specifically, the myoglobin within the muscles.

In order to suspect a diagnosis of ER, the clinical signs, combined with an accurate, and honest, history is what is needed. But to ­confirm the diagnosis, your vet needs to ­submit blood samples which test for two ­important enzymes: CK and AST.

These enzymes are released into the blood stream soon after excessive muscle ­exertion, and are the consequent result of massive ­muscle damage at the cellular level, and ­elevated levels of these enzymes combined with the clinical signs should be sufficient to confirm the diagnosis.

Treatment

­Firstly, the most important thing is to restrict the horse’s movement to an absolute minimum. So often we think that walking them to “loosen up” is the best thing. Not so! Well not initially anyway.

Secondly, we would like to control the ­inflammation and pain. Use non-steroidal anti-­inflammatories, but only if the horse is not ­excessively ­dehydrated as most anti-­inflammatories can cause kidney damage in a dehydrated animal.

Thirdly, apply as much tender loving care as you can. By this I mean supportive therapy such as gently massaging the large ­muscle groups to relieve them of the lactic acid ­build-up. Also, keep the “patient” warm and dry, and only start walking when the horse is ­moving around freely and the urine colour ha­s returned to normal. Good quality hay and fresh water are also very important.

Lastly, and possibly most importantly, is to restore the fluid status of the horse – this will not only rehydrate the horse, but this will also help to support and “flush” the kidneys – bear in mind that the discoloured urine is full of myoglobin that must be ­filtered by the kidneys, thus causing ­extensive ­damage to them. Offering water or tubing the horse is often not sufficient in order to give the ­kidneys the necessary ­support. It is often necessary, and always a good idea, to put the horse on a drip.

Management practices

You have all heard (ad nauseum!) that ­prevention is ­better than cure – which is true, but this is not ­always ­guaranteed in the case of ER. A few ­management practises can be ­implemented to help reduce the incidence and severity of ER cases. After an ER episode, very gradually ­re-introduce exercise and carbohydrates.­

Also, limit the quantity of carbohydrates in the “recovery” ration – rather include slightly higher levels of canola or corn oils to provide energy from an oily, but non-carbohydrate source.

Depending on the severity of the initial ­episode, it may be necessary to monitor blood levels of CK and AST. Gradually increase the exercise period by 1-3 minutes per day – do not break this rule, otherwise you will either limit the horse’s performance or ­predispose it to another bout of ER at a later stage.

Supplementing their diet with anti-­oxidants such as Vitamin E can also prove useful. ­Another very important management tool is to have a different ration for rest days (a ­ration that is lower in carbohydrates). This will also help to keep the highly strung breeds less “hot”. Because of the relation to stress, it is also a good idea to limit this by providing a “companion” or friend for the competing or travelling horse.

Courtesy to Dr M Walton, for a written ­contribution to this article. Other references available from the author. SAH