A 2.5 week old Holstein bull calf was presented with two other bull calves to the Cornell University Equine and Farm Animal Hospital as part of a herd outbreak investigation of infectious diarrhea in January 2013. This calf also had a history of being found acutely down. Initially the mentation and fluid volume status of the calf improved with supportive care. However, the calf continued to be recumbent in the face of aggressive treatment and the condition of the pelvic limbs deteriorated over two days until there was a palpable temperature difference between the distal thoracic and pelvic limbs and there was no motor function in the pelvic limbs. The hoof capsules of the pelvic limbs became cyanotic. Lactate concentration was measured in a venous sample from the right distal thoracic limb (1.2 mg/dL, reference interval, 0.9-1.7 mmol/L) and compared to a venous sample from the right distal pelvic limb (3.7 mg/dL, reference interval, 0.9-1.7 mmol/L) as an evaluation for saddle thrombosis. The differential lactate concentrations were interpreted to indicate that there was significant compromise to the blood supply of the pelvic limbs, supporting a diagnosis of saddle thrombus. Saddle thrombus is a common term used to refer to thromboembolism at the level of the aortic trifurcation. The suspected cause of the saddle thrombus in this calf was sepsis secondard to Escherichia coli infection.