Causes of Mortality of Dairy Cattle Diagnosed by Complete Necropsy

This retrospective case series summarized the primary causes of death in 857 dairy cattle necropsied from 2008 to 2019 at the Utah Veterinary Diagnostic Laboratory, from dairy farms in Utah (76%), Idaho (16%) or other states (8%), primarily in the U.S. Intermountain West. Of cattle with age provided, 74% matched with body weight based estimates for those with no age stated. Cattle ranged from fetuses at 60 days of gestation to 9 years old. Primary cause of mortality was diagnosed in 833 cattle (97%); no cause was evident in 24 cattle (3%). Sexes were female 620 (72%), male 214 (25%), not recorded 23 (3%). Seven diseases killed 80% of the animals: gastrointestinal disease (most enteritis/colitis) 318 (37%); pneumonia 166 (19%); abortion 96 (11%), peritonitis 30 (4%), omphalophlebitis (navel ill) 27 (3%), abomasitis 23 (3%), and metritis 23 (3%). Etiologic agents and specific causes varied with age categories of the animals. Young calves that died from dystocia, omphalophlebitis, or congenital abnormality often presented with no suspicion of those causes by the owners because of no external signs. Some important fatal diseases of adult dairy cows that are often diagnosed ante-mortem were diagnosed at necropsy with no suspicion by those submitting the carcasses: metritis, hardware disease, and displaced abomasum. Multicentric lymphoma was a relatively important cause of death in cows more than 4 years old. Despite use of a toxicology laboratory, toxicity was only diagnosed as causing 1% of the deaths across all ages of dairy cattle. There were numerous other causes of mortality diagnosed as well. Necropsy is a vital tool to diagnose causes of death in dairy cattle and can guide changes in management or preventive practices to reduce the rate of deaths in dairy herds.