POLIOENCEPHALOMALACIA IN CATTLE CONSUMING WATER WITH ELEVATED SODIUM-SULFATE LEVELS - A HERD INVESTIGATION

Polioencephalomalacia (PEM), hereafter used to refer to the specific l esion of cerebrocortical necrosis, developed in 11 of 110 mature cattl e on pasture in central Saskatchewan. The primary water source contain ed a markedly elevated level of sodium sulfate (7200 ppm). The signifi cant clinical findings of the herd investigation included depression, ataxia, cortical blindness, dysphagia, and death. Diagnosis of PEM was confirmed by histopathological evidence of cerebrocortical and subcor tical necrosis with microvascular fibrinoid necrosis predominantly in the thalamic region of three affected cattle. The histopathology of su lfate-associated PEM observed in this herd appears to be unique and it s features are presented and discussed. Mean levels for serum transket olase, copper, red blood cell transketolase activity, and thiamine (vi tamin B1) in all exposed young (n = 100) and mature (n = 99) animals d id not reveal evidence of deficiencies. Although the blood thiamine st atus of the seven surviving, affected animals was not evaluated before treatment with exogenous thiamine, 199 members of the herd had blood thiamine levels within the reference range at the time of the outbreak . The outbreak resolved after cattle were moved to a water source cont aining acceptable levels of sodium sulfate.