Toxicity of Bassia hyssopifolia to sheep.
B. hyssopifolia, an introduced annual, is toxic to sheep. Signs of poisoning in sheep dying from acute bassia intoxication included weakness, incoordination, tetany and coma. The toxic principle was probably an oxalate. On the basis of oxalate content, bassia was more toxic than halogeton (Halogeton glomeratus), another oxalate-producing plant (lethal dose 0.55-0.66 g/kg body weight for bassia compared with 1.06 g/kg for halogeton). Sheep grazing halogeton can adapt to the oxalate and survive whereas sheep on bassia fail to adapt. The average serum Ca of 5 sheep that died within a few h from acute poisoning after receiving 350-450 g of bassia by stomach pump dropped from 10.9 to 3.6 mg/cm3; that of 2 sheep dying after 17 and 22 days, during which time increasing amounts of bassia (324 to 500 g) were fed at spaced intervals, dropped from 10.9 to about 8.8 mg/cm3. B. hyssopifolia should not be further sown or allowed to increase, and care should be taken when grazing livestock on existing stands.<new para>ADDITIONAL ABSTRACT:<new para>Seven ewes fed by stomach tube with dried flowering plants of B. hyssopifolia, an introduced annual, died, five after a single feeding and two after irregular feeding for 17 and 22 days. Signs of poisoning in sheep dying of acute Bassia poisoning included weakness, incoordination, tetany and coma, and haemorrhages occurred over the surface of the rumen. The other two had enlarged kidneys but few other gross lesions. The toxic principle in Bassia is thought to be an oxalate. Bassia poisoning is in many ways comparable with Halogeton poisoning, but Bassia is more toxic possibly because of a difference in the chemical form of the oxalate. Other changes observed in the sheep which died of acute Bassia poisoning were a large drop of serum Ca concentration, from 10.9 to 3.6 mg/ml and an increase in SGOT from 93.6 to 215 units/ml.