Equine Health: Stomach Ulcers in Racehorses


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Stomach Ulcers in Racehorses
By ABC TV program " Catalyst"

Stomach ulcers prevalent - claims TV program

In a recent edition of the ABC TV science program "Catalyst", it was claimed the prevalence of stomach ulceration in racehorses in training is higher than previously recognised.

Dr Leanne Begg (Specialist in Equine Medicine Randwick Equine Centre) and Dr Craig Suann (Senior Official Veterinarian NSW Thoroughbred Racing Board) have collaborated to compile the following essay titled "Management strategies for gastric ulceration in racehorses":
Overseas studies have shown that a significant proportion of performance horses examined by gastro-endoscopy has evidence of gastric ulceration, although not all of these horses show actual clinical signs.

A recent study conducted by the Randwick Equine Centre in Sydney where 304 thoroughbred racehorses in training were gastroscoped demonstrated an occurrence of gastric ulceration similar to that reported in the overseas studies.

The common clinical signs observed in horses with gastric ulceration can include a reduction in appetite, loss of body weight and condition and suboptimal performance.

However, many horses are asymptomatic. Ulcers tend to be more severe in older horses and horses that have been in training for a greater length of time.

The only way to definitively diagnose gastric ulceration is by a veterinarian performing an endoscopic examination of the stomach.

A three metre long endoscope is required to adequately examine the entire stomach of an adult horse.

Causes of Gastric Ulceration

High concentrations of hydrochloric acid in the stomach are thought to be a major factor in the production of gastric ulcers.

Horses secrete gastric acid continuously since they have evolved as forage feeders, grazing continuously over a 24-hour period in the natural state. In some horse stables, there can be periods of time when acid levels in the stomach of horses are high.

This is because there has been the tendency to feed grain meals two to three times per day while limiting the amount of hay between some of these meals.

Eating causes release of bicarbonate-rich saliva which buffers the acid production, and the feed itself also neutralises the effects of the acid.

During periods of feed deprivation, however, the acid level in the stomach soon rises.

The lower part of the stomach has a protective lining of mucous and bicarbonate, but the upper part of the stomach is prone to damage from this high level of acid and is the usual site of ulcer formation.

Management Strategies

Management strategies such as continual access to hay will aid in lowering acid levels in the stomach and reduce the incidence and severity of clinical signs.

Some leading racing stables allow their horses unlimited access to hay, whether it be lucerne hay, long stick oat hay, or meadow hay, depending on season and availability and the preference of the horses.

It has been shown that continual access to hay will usually not affect the intake of grain and/or hard feed, in fact good hay eaters are invariably good grain eaters.

Continual access to hay may also lower the incidence of certain behavioural disorders in stabled horses.

Minimising the use of non-steroidal anti-inflammatory drugs such as phenylbutazone, as well as corticosteroid preparations, is also important.

These drugs inhibit the formation of certain prostaglandins (PGE2) in the stomach. PGE2 is known to enhance the secretion of bicarbonate-rich mucous and promote mucosal blood flow in the lower part of the stomach, as well as to suppress hydrochloric acid production.

Inhibition of PGE2 by the administration of these drugs will reduce its protectant effects on the stomach mucosa and may exacerbate ulcer formation.

Medical treatment of gastric ulcers is aimed at reducing the hydrochloric acid level in the stomach.

Several classes of drugs can do this, however only ranitidine has been registered in Australia for use in horses.

Ulcerguard® is a registered paste formulation of ranitidine that is given orally three times per day.

Trainers are reminded that ranitidine is a Schedule 4 prescription animal medicine, and should only be used under veterinary supervision.

Detection studies examining Ulcerguard® paste have been recently conducted and demonstrate that it can be used in horses in work, albeit with some restrictions pre-race.

For information on the results of these studies, you should consult your veterinarian or the TRB Veterinary Department on (02) 8344 5050.