Causes of mortality in farmed white-tailed deer in the midwestern United States, 2004–2023

Farmed cervids are of growing economic importance in the midwestern United States. Although diseases of wild and captive cervids have been examined in more northerly climates, little information exists on the health challenges of deer in the Midwest. We characterized and summarized the causes of mortality in farmed white-tailed deer (<i>Odocoileus virginianus</i>) submitted to the University of Missouri Veterinary Medical Diagnostic Laboratory (Columbia, MO, USA) over a 19-y period (2004-2023). Of 388 cases examined, 253 (65%) were carcasses submitted for autopsy, and 135 (35%) cases were tissue samples harvested by field veterinarians. Infectious disease was the most common cause of mortality (<i>n</i> = 335; 86.3%). Of infectious causes, primary pneumonia was most common (<i>n</i> = 140; 41.7%), followed by septicemia (<i>n</i> = 68; 20.1%), and primary enteritis (<i>n</i> = 64; 19.1%). Viruses were detected in 18% of pneumonia cases. The most common non-infectious diagnoses were emaciation and trauma (both 4 each; 1%). Thirteen animals (3.4%) died of unknown causes. Forty-nine percent of cases were juvenile deer <1-y-old. Most cases were received in the summer (212; 54.6%). Infectious diseases, particularly bacteria and viruses, pose a significant health challenge to farmed deer in the midwestern United States.