Abstract
This case report describes the poisoning of two mares from the same paddock with Robinia pseudoacacia (Black locust) bark. The poisoning manifested itself by the sudden onset of weakness and fever with transient improvement after the administration of non-steroidal anti-inflammatory drugs and fluids. After the initial stabilisation, the mares were left unattended overnight. One of them was found dead in the morning. The surviving mare developed colic and severe encephalopathy and had to be referred to the clinic. Blood tests revealed severe hyperammonaemia. After four days of symptomatic treatment, she fully recovered. Robinia pseudoacacia with bark freshly bitten off was found in the paddock. The necropsy of the dead mare revealed oedema of the brain and lungs, pleural haemorrhages, and hyperaemia and haemorrhages of the glandular mucosa of the stomach. The intestinal content was watery, without macroscopic findings of the bark. Due to the peracute onset in both mares at the same time, hyperammonaemia and paralytic ileus in the surviving mare, and the presence of Robinia pseudoacacia in the paddock, poisoning with this tree was highly suspected. The diagnosis was confirmed by the microscopic findings of Robinia pseudoacacia bark tissue in the gastric content of the dead mare.