Oxalate (Halogeton) poisoning of sheep: certain physiopathologic changes

Certain clinical changes associated with acute oxalate (halogeton) poisoning were determined in sheep given (by stomach tube into the rumen) a lethal dose of Halogeton glomeratus. Plasma concentrations of calcium and calcium ion activity decreased over several hours to such low levels that tetany or coma occurred and death followed. Cerebrospinal fluid concentrations of calcium did not reflect the degree of hypocalcemia. In 2 pregnant sheep administered halogeton, the plasma concentration of calcium in the fetus did not decrease despite the appearance of severe maternal hypocalcemia. Increases in plasma total inorganic phosphate and magnesium concentrations occurred as the hypocalcemia progressed. Hyperglycemia was often marked as hypocalcemia became severe; however, as hyperglycemia increased, plasma immunoreactive insulin concentrations remained inappropriately low in relation to the plasma concentration of glucose. Intravenous infusion of a calcium solution at this time was associated with marked increase in immunoreactive insulin concentration and a decrease in glucose concentration. Ruminal activity, as measured by frequency and amplitude of contractions of the rumen, was greatly reduced as hypocalcemia progressed. Seemingly, body temperature became lowered as severity of the hypocalcemia progressed. Seemingly, body temperature became lowered as severity of the hypocalcemia increased, as determined by intramuscularly or intraperitoneally implanted temperature telemetry devices. However, the occurrence of tetany and the fleece covering could either modify or reverse this decrease in body temperature.