Progressive encephalopathy with pseudolaminar cortical necrosis in cattle associated with consumption of young Tifton 68 grass (Cynodon nlemfuensis Vanderyst)

Tifton 68 (Cynodon nlemfuensis) is a cyanogenic forage grass that may also contribute to dietary sulfur exposure. Young Tifton 68 was introduced into a 32-animal dairy herd. Within approximately 2 days, neurological disease was recognized; eight cattle were affected and four died. Affected cattle developed visual and postural deficits, hypermetria, intention tremors, recumbency, and convulsions. The forage produced a rapid positive reaction in the qualitative sodium picrate paper test. Neuropathological examination of one cow revealed bilateral pseudolaminar cortical neuronal necrosis with selective deep gray-matter and cerebellar injury. The outbreak was strongly associated with Tifton 68, but cyanide exposure was not analytically confirmed and total sulfur exposure was not determined, leaving cyanide exposure and sulfur-associated polioencephalomalacia as competing etiological hypotheses.