For a number of years, calves around 3 months of age had been dying suddenly with the only sign prior to death being bloating. A recently deceased calf was autopsied in early September 2011 and found to have extensive peritonitis. A perforating ulcer was found in the abomasum. Abomasal ulceration in calves is associated with stress and pH change in the abomasum.
Deaths under similar circumstances have occurred on this grazing property on the western slopes of the Northern Tablelands over the past 5 to 10 years. Occurrence has been sporadic and the number of cases varies from year to year. No records existed to provide more detail in this area. The affected calves had been around 12 weeks of age. The cows were all Santa Gertrudis or Santa cross, grazing improved pasture or oats.
Deaths with similar clinical signs had been investigated in the past. Previous diagnoses had been linked to enterotoxaemia. Modification of the vaccination program to include a pre-calving 5 in 1 booster for cows had been undertaken.
The case reported here is the second death of calves around this age this year.
The calf was found dead up against a fence. It had been observed bloated the evening before and dead the next morning.
When the abdomen was opened at autopsy, approximately 100mL of brown, smelly liquid escaped the abdomen. At the display stage (Image 1), the abdomen was found to have adhesions and pus on the serosal surface of the stomachs, omentum, liver, diaphragm, abdominal wall and small intestine.
The surface of all of the organs was reddened. The abomasum had a number of red patches approx 1cm in diameter on the serosal surface. One of these had a dark red, blackish centre and communicated with the abomasal lumen.
The abomasal mucosa was thickened and oedematous. There were patchy, small, dark red haemorrhages over the mucosal surface. These haemorrhages were more dense around the ulceration.
A number of diseases exotic to Australia are characterised by ulceration of the gastrointestinal tract. These include Rindepest. In older cattle, malignant catarrhal fever and BVDV are possible causes. Ulcers are also common in milk fed dairy calves consuming milk or dairy replacer. Two to four month old, well-nourished suckling beef calves may be affected, and they often have trichobezoars in the abomasum (1. Merck Veterinary Manual, online).
There is also reference to the pH in the abomasum decreasing if the calf inadvertently goes off its food (1. Merck Veterinary Manual, online). Therapy when treating possible abomasal ulcer cases is to encourage continual flow from the forestomachs to the abomasum as this will increase pH (1. Merck Veterinary Manual, online).
In this case the milk clot was no longer in the abomasum but had passed through into the small intestine. There was very little grass in the developing forestomachs. No hyperaemia was present in the forestomachs so the pH in these areas may have been less acidic. The hyperaemia did not extend into the small intestine.
These cases are very sporadic and have not been possible to predict. If another bloated animal was detected, therapy would involve increasing abomasal pH using an antacid. The bloating is likely to be as a result of peritonitis so antibiotics would be indicated if detected early. In grass fed unweaned calves it is difficult to predict any practical preventative measure.