Neurologic disease in range goats associated with Oxytropis sericea (Locoweed) poisoning and water deprivation.

About 200/2500 Spanish goats foraging on mountain rangelands of western Montana developed neurologic disease with severe rear limb weakness, knuckling of the rear fetlocks, and a hopping gait. Sick goats were of all ages and in good flesh, though they often had dull, shaggy coats. Some mildly affected animals recovered after being moved to feed lots, but others progressed to recumbency, seizures and death. At necropsy both moribund and clinically affected animals had few gross lesions; 1 animal had contusions and puncture wounds on rear legs and perineum, suggestive of predator bites. Histologic lesions included mild vacuolation of neurons and visceral epithelial cells, mild diffuse cerebral edema with minimal neuronal pyknosis, and random, multifocal Wallarian degeneration of spinal cord axons. Affected animals had elevated serum sodium, potassium and chloride levels; other mineral analyses and serum biochemistries were within normal limits. Locoweed-induced depression and inhibition of neuromuscular function coupled with water deprivation due to predation pressure allowed development of neurologic disease and hypernatremia.