No gross or histopathological changes indicative of PEM were detected in the brains of the heifers. Of note, during the course of the present study, we documented an outbreak of S-induced PEM in commercial feedlot steers. Brain thiamine variables in experimental animals fed HS diet were then contrasted with brain thiamine status in PEM affected feedlot steers. Interestingly, in clinically normal animals, exposure to HS diet resulted in increased levels of both TMP and TPP in the brain tissue, in comparison to animals fed LS diet. In contrast, the PEM affected brains showed overall lower levels of thiamine phosphates. It is noteworthy that TPP levels were 36.5% lower, despite 4.9-fold higher free thiamine in PEM brains compared to normal brains