Pica is defined as 'the ingestion of materials other than normal food'. The most common type of pica in cattle is osteophagia, or 'bone eating'. Bone eating is generally considered to be because of either phosphorus deficiency or a behavioural trait. In this case the cause of the pica was not determined but the fatal sequelae was penetration of the reticulum.
A ten year old Hereford cross cow with a two month old calf at foot was reported to be losing weight and lethargic. She was part of a small herd of house cows grazing mature forage lucerne. Her ill health had only been apparent for five days but, having been unobserved for a couple of weeks, the course of her illness may have been longer. The owner noted some laboured breathing the morning of attendance. The cow died 30 minutes prior to attendance at the property. She was in right lateral recumbency in the stock yards. There was no evidence of kicking or struggling prior to death. Oral mucosa could still be assessed as pale. Some blood around the eyes, perineum and vulva was attributed to trauma from crows.
At post-mortem there was approximately 600mL of brownish fluid in the pleural space. Lung tissue was consolidated in patches, had areas of haemorrhage, thickened yellow areas and fibrin adhesions. There was some interstitial and interlobular emphysema in the lungs. There was a large football sized mass of congealed blood in the left cranial area of the chest. White bands of tissue ran longitudinally through the myocardium. There was 50mL of brownish fluid in the pericardial sac. The pericardial sac appeared intact.
The liver was swollen, especially in dorsal lobes, appearing 15% larger than normal. It had a yellow tinge with petechiae throughout. The omasum appeared to be abnormally large. On incision into the reticulum two long bones were located. One of these bones, a 20 centimetre piece of kangaroo fibula, was perforating the reticulum to a depth of about 15 centimetres. The bone tracked through the liver and into the chest cavity. It terminated in mediastinal tissue.
Osteophagia is commonly associated with phosphorus deficiency in Australia. While the phosphorus status of this herd was not determined, the case occurred on black soils (traditionally higher in phosphorus than red soils) and on grazing lucerne. Phosphorus deficiency is therefore unlikely.
The cause of death in this case appears to have been a ruptured blood vessel in the chest cavity. This is evidenced by the pale appearance of the cow before necropsy and the large blood clot found in the chest. The bone foreign body appears to have tracked up into the chest causing inflammation and infection causing dyspnoea and secondary rupture of the weakened vessel. This would explain why the owner had described the cow on its feet that morning and sudden death a short time later. The owner was advised to clean up any carcasses observed or shot on the property.