Gangrenous Ergotism (similar to fescue foot in winter-grazing cattle) in a cow, caused by ingesting ryegrasses or bromes infected with the parasitic fungus Claviceps purpurea. Can immediately cause hyperthermia (fever) and hypersalivation. The repeated constriction of the arterioles at first causes decreased blood flow to the extremities, and eventually (generally not before 2 months of exposure) causes terminal necrosis of extremities due to thrombosis.
It’s pretty gory condition as it progresses. The necrosis starts with dry gangrene around the fetlock or pastern, and animals that continue to eat ergot-infected grasses or feed can have their hooves, ears, and tail tips literally fall off. o_o
Ergotism info from my production management classes, but can be read about at Merck Veterinary site.
Photograph from “Special Report on the Diseases of Cattle”, put out by the U.S. Department of Agriculture, Bureau of Animal Industry. 1912.