Polioencephalomalacia (PEM) is a neuropathologic condition of ruminant
s that can be induced by a variety of neural metabolic disruptions. Th
ese include altered thiamine status, water deprivation-sodium ion toxi
cosis, lead poisoning, and high sulfur intake. Investigations of sulfu
r-related PEM have demonstrated that the onset of the clinical signs c
oincides with excessive ruminal sulfide production. A number of rumina
l factors could modulate the production and absorption of ruminal sulf
ide. The development of a convenient method to estimate ruminal gas ca
p H2S has made it possible to identify cattle with high levels of rumi
nal H2S and evaluate their risk of developing PEM.