A young beef calf developed severe diarrhea and fever that did not respond to multiple antibiotics. The calf had an underdeveloped immune system (missing thymus gland) and was treated with many antibiotics and steroids, which weakened its immune system further. After death, examination revealed the calf had a widespread fungal infection caused by Lichtheimia ramosa in the liver and digestive tract, representing the first documented case of this type in Japanese Black cattle.