Locoweed Poisoning in a Northern New Mexico Elk Herd

Abstract

Locoweed (Oxytropis sericea) poisoning was confirmed in 16 free-ranging elk (Cervus elaphus nelsoni) from northern New Mexico over a 5-year period, 1977-81. Clinical signs consistently seen were emaciation, weakness, incoordination, muscular trembling, posterior ataxia, lethargy, and visual impairment. Gross morphologic changes included hydrothorax, hydroperitoneum, hydropericardium, meningeal edema, serous atrophy of fat deposits, and anemia. Consistent histological changes were widespread cytoplasmic vacuolation in the parenchyma of most major organ systems. This outbreak of locoweed poisoning coincided with poor range condition exacerbated by subnormal precipitation, and was not considered to be a significant mortality factor in the elk herd. However, locoweed poisoning may significantly affect population dynamics of elk herds restricted to ranges severely infested by locoweed.