Nine Holstein cows were died between 3 October and 13 December of 2009 in Turkey. On this farm, all the dairy cattle (350) were being fed in two groups by the owner. The only difference between the rations was that the ration of group 2 was containing hairy vetch hay. It was noticed that all (except one dead) animal were in the Group 2. Clinical signs in affected animals prior to death were generally dramatic drop in milk yield, inconsistent fever, diarrhea, cutaneous lesions, listless, ruminal stasis, conjunctivitis, icterus, red urine and abortion in the pregnant animal. Anemia and Babesia bigemina were detected in hematologic analysis. There was disseminated vacuolar degeneration around vena centralis in liver, and the epithelium of the proximal tubules had severe swelling and had deeply eosinophilic epithelial cells and the lumens of tubules were disappeared in kidneys. It is considered that the cases presented here are mainly caused by hairy vetch as no more clinical signs and deaths were seen after 10 days of removal of hairy vetch from the animals’ ration.

Key words: Babesiosis, Dairy cow, Deaths, Hairy Vetch (Vicia villosa)