Protective effects of antioxidants on bitterweed (Hymenoxys odorata DC) toxicity in sheep.

Antidotal effects of the 2 antioxidants butylated hydroxyanisole (BHA) and ethoxyquin (EQ) were evaluated in bitterweed (Hymenoxys odorata DC) toxicosis in sheep. Bitteerweed contains a toxic sesquiterpene lactone, hymenoxon, the toxicity of which is reduced by cysteine. Both BHA and EQ are known to induce hepatic glutathione production in rodents. Treatment of sheep with EQ (2.5 g/sheep/day for 9 days before poisoning) gave significant protection from toxic doses of bitterweed, but the protective effect of BHA was insignificant. Of 6 sheep given EQ in the feed, 5 survived 7 doses of bitterweed (4 g/kg/day or higher for 7 days), whereas 5 of 7 controls and 4 of 7 sheep given feed with added BHA died. The added EQ in the feed decreased the serum alkaline phosphatase activity and total protein, albumin, and calcium concentrations. Seemingly, EQ is the first protective agent with field application potential for bitterweed toxicity.