Kate Hore RNutr(Animal). Snr Nutritionist at NAF
Once known as Monday morning disease, Azoturia, more correctly known as Equine Rhabdomyolysis Syndrome (ERS), can affect any horse, though mares seem to be more susceptible. Most commonly seen in horses which have been exercised following a period of rest, but without altering their dietary intake. As horses were not used on Sundays traditionally, Monday morning was the prime time to witness the problem, hence the name.
Concentrate diets, high in starchy carbohydrates, are a factor in the development of this problem, particularly if they are being fed high levels of straight feeds such as oats, though this is becoming increasingly uncommon. Signs usually become apparent just after strenuous exercise has started. The rider may become aware that the horse is not moving correctly or is unable to go forward. Trying to continue work will only succeed in exacerbating the problem and may cause permanent damage to muscle tissues. Azoturia is a very painful problem, as the muscles cramp and spasm, making it difficult to move. Often this will occur on a hack, as a common exercise following strenuous exertion, and the rider should resist the temptation to ride back to the yard – instead arranging transport to collect the horse.
Considerable damage to muscles is caused by enzyme activity, which can lead to breakdown of the muscle tissues, seen in a red colour in the urine due to presence of myoglobin from the muscle. This may even lead to irreparable kidney damage in the worst cases, so should be seen as a serious disorder. Recent research has shown that most of the horses who now suffer with Azoturia have Equine Polysaccharide Storage Myopathy (EPSM), which results in extreme levels of glycogen and polysaccharides within muscle cells. This can be diagnosed via biopsy, with samples usually taken from around the tail.
Feeding low starch diets, and including higher levels of fats, such as oil, can help reduce the risk of tying up. The ideal diet is based on fibre or forage, fed at roughly 2% of the animals bodyweight, providing plenty of digestible energy as oil and limiting starch to less than 10% of daily digestible energy. It must also be considered that energy provided by the diet should not exceed their requirements, in order to prevent excessive weight gain. In conjunction with gradual turnout time increases and exercise, this should help decrease incidences of Azoturia.