Abomasal ulcers are defects in the mucosal lining of the abomasum. They are difficult to diagnose unless there is perforation of the abomasal wall or erosion into a blood vessel. Even then, the leakage of ingesta or blood must be significant.
The causes of abomasal ulceration in cattle are not well understood. Prolonged inappetence resulting in sustained high acidity in the abomasum is considered an important risk factor. Stress, high dietary fibre in calves, and inadequate dietary fibre in adults are also believed to play a role. Rarely, in older cattle, ulcers are associated with tumours infiltrating the abomasal wall. Multiple shallow erosions and ulcers affecting the abomasum are also found at necropsy in viral diseases of cattle such as bovine virus diarrhoea and malignant catarrhal fever. Prolonged treatment with high doses of non-steroidal anti-inflammatory drugs or antibiotics or both may also cause abomasal ulceration.
Deaths from both perforated and bleeding abomasal ulcers have been recorded in cattle at sea.
Cattle with ulcers may show signs of colic (lifting hind legs and looking at the flank) and grinding of teeth (bruxism). Chronically affected cattle may lose body condition.
Additional signs may be related to severity of blood loss (pale mucous membranes, weakness, elevated heart and respiratory rates), and black tarry faeces (melaena). Animals may die suddenly if blood loss is extreme. Black tarry faeces also occurs when blood from the respiratory tract is coughed up, swallowed and digested in the abomasums, therefore caudal vena caval syndrome should be considered as a differential diagnosis. Bright red blood coating formed faeces is usually from the large intestine in which case coccidiosis should be considered. Dull red blood is usually from the small intestine, and may indicate salmonellosis or intussusception. Haemorrhagic bowel syndrome (HBS) is a sporadic, acute necrohaemorrhagic enteritis that has been reported in cattle in Australia and overseas, with signs similar to those described for abomasal ulcers.
Cattle with perforated ulcers may develop local peritonitis and recover fully if adhesions are not extensive, or they may develop acute diffuse peritonitis and die. The outcome depends on the amount of leakage into the abdomen and whether it is contained by the omentum. Animals affected with local peritonitis will have fever, inappetence, and a pain reaction to deep palpation of the right side ventral abdomen. Those with acute diffuse peritonitis will deteriorate and die quickly with sunken eyes, cold clammy skin and rapid, shallow breathing and pulse.
At necropsy, one or more ulcers will be present in the abomasal mucosa ranging from a few mm to 5cm in diameter. They are easily missed. Examination under a good light following rinsing of the mucosa with water will assist detection. In cattle dead from a bleeding ulcer, findings include pale mucous membranes, watery blood, shriveled and empty intestines, black and tarry faeces, and blackened fluid within the abomasum. Washing of the ulcer may reveal an eroded blood vessel. Perforated ulcers are often associated with pockets of fluid and pus within the abdomen, possibly trapped within folds of omentum.
Death from other gastrointestinal accidents may resemble deaths from haemorrhage or perforation of the abomasum. If acute diffuse peritonitis is found at necropsy, it is important to determine the cause - the preventative measures against ulceration are different from traumatic reticulitis.
If abomasal ulceration is suspected, minimise stress, stop any treatments with non-steroidal anti-inflammatory drugs. Systemic broad spectrum antibiotics are generaly recommended for protection against infection. Feed animals increased roughage (hay or chaff) to keep the animal eating and also stimulate salivary production to counteract acid production within the abomasum.
Oral antacids such as magnesium hydroxide and sodium bicarbonate are ineffective because they are unlikely to reach the abomasum in adequate amounts to counter acidity.
For animals weak and lethargic with anaemia from bleeding abomasal ulcers the prognosis is poor, even if transfusion of blood is available. A minimum of 4-6 L may be lifesaving but there is a possibility bleeding may continue.
Broad spectrum antibiotics (oxytetracycline, trimethoprim sulpha) are recommended because of the risk of infection including localized peritonitis and adhesions.
For animals with acute diffuse peritonitis, the prognosis is extremely poor, and euthanasia should be considered if the animal is recumbent, sunken eyed, the heart rate exceeds 120 beats per minute and the skin is cold and clammy. The rare animal surviving may become chronically illthrifty from adhesions within the abdomen.
Minimise stress, feed roughage and keep animals eating to avoid long periods of overly acidic conditions occurring in the abomasum.