Ovine Polioencephalomalacia Associated With Dietary Sulphur Intake

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Abstract
Fifty-six female crossbred two-month-old lambs were housed in individual cages, and fed a basic ration of barley (59%), soybean meal (5%), and alfalfa (32%) prepared to meet NRC nutrient requirements. Four percent of the diet contained a standard salt mix to which the factors inorganic sulphur (S) and thiamine (B1) were added. Four treatment groups were used: low sulphur and normal thiamine (0.19% S, 13.7 mg/kg B1) low sulphur and high thiamine (0.19% S, 243 mg/kg B1), high sulphur and normal thiamine (0.63% S, 13.7 mg/kg B1), high sulphur and high thiamine (0.63% S, 243 mg/kg B1). All animals had free access to water and were offered 1 kg/animal/day of diet for 14 weeks, when necropsy was undertaken. Seven lambs fed unsupplemented (normal B1) diets containing added sulphur developed clinical symptoms of polioencephalomalacia (PEM) between the 3rd and 7th week of the trial. Morbidity (P less than 0.013) and mortality (P = 0.08) differences were attributed to S administration. None of the B1 supplemented lambs developed clinical signs of PEM. Body weight and relative organ weights did not differ among treatment groups. Serial sections of all brains were examined grossly and microscopically. Nonparametric statistical analysis revealed sulphur related effects in the cerebrum, midbrain and hindbrain (P less than 0.0001), no thiamine-related effects or interaction between the factors were seen, except in the amygdaloid body. It was concluded that inorganic sulphur was associated with polioencephalomalacia, and that dietary thiamine may decrease the severity of lesions in some affected areas of the central nervous system.