Jayme, from the Merck Vet Manual -- and I know you have done a bunch of research yourself...
Polioencephalomalacia (PEM) is an important neurologic disease of ruminants that is seen worldwide. Cattle, sheep, goats, deer, and camelids are affected. The term PEM denotes a lesion with certain gross and microscopic features that are not specific for a particular etiology or pathogenesis. Historically, PEM has been associated with altered thiamine status, but more recently an association with high sulfur intake has been observed. Other toxic or metabolic diseases (eg, acute lead poisoning, sodium toxicosis/water deprivation) can result in PEM as well.
A variety of sulfur sources can result in excessive sulfur intake, including water, feed ingredients, and forage. Many geographic areas have surface and deep waters high in sulfate.
Alfalfa, by virtue of its high protein and sulfur-containing amino acid content, can serve as a significant source of sulfur. Although grasses tend to be low in sulfur, some circumstances can result in high sulfate concentrations. Certain weeds, including Canada thistle ( Cirsium arvense ), kochia ( Kochia scoparia ), and lambsquarter ( Chenopodium spp) can accumulate sulfate in high concentration. Cruciferious plants normally synthesize sulfur-rich products and serve as important sources of excess sulfur. These include turnips, rape, mustard, and oil seed meals. Byproducts of corn, sugar cane, and sugar beet processing commonly have a high sulfur content, apparently due to the addition of sulfur-containing acidifying agents. PEM ( has been associated with the use of these types of byproducts as feed ingredients. A high molasses-urea diet has been associated with a form of PEM that lacks altered thiamine status.
Dietary supplementation of thiamine at 3-10 mg/kg feed has been recommended for prevention, but the efficacy of this approach has not been carefully evaluated. During a PEM outbreak, sufficient roughage should be provided. When the problem could be associated with high sulfur intake, all possible sources of sulfur, including water, should be analyzed and the total sulfur concentration of the consumed dry matter estimated. Dietary ingredients or water with high sulfur concentration should be avoided; if this is not possible, then more gradual introduction to the new conditions can improve the chances of successful adaptation.
This was a good article too
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