AbstractBackgroundAlthough significant efforts have been put into restituting the European bison (Bison bonasus) and increasing its population, it remains a globally endangered species and requires conservation. Protection programs of bison indicate the need for morphological studies of their individual systems, in order to enhance restitution programs and enable appropriate veterinary care. The aim of this study was to investigate the morphology of the coronary veins of the European bison (Bison bonasus).ResultsThe study was carried out on 78 hearts of European bison of both sexes, aged 5 to 21 years. The subepicardial veins were clearly visible after being filled with dyed synthetic latex (LBS 3060), Plastogen G and Batson’s No. 17. In all the studied animals, the great cardiac vein drains into the coronary sinus. The interventricular paraconal branch and the circumflex branch of the great cardiac vein were distinguished. The left marginal vein, which originated in the apical area or halfway along the length of the left ventricular margin, was easily identified in 65 animals (83%). In most animals (51 bison, 65%), the middle cardiac vein drained into the coronary sinus, while in some animals it drained into the right atrium (27 animals, 35%).ConclusionsBlood from the cardiac walls is drained into the great cardiac vein, the middle cardiac vein, the right coronary veins and numerous small cardiac veins.