Effects of bitterweed (Hymenoxys odorata) on voluntary feed intake and serum constituents of sheep.

Effects of daily dosing with bitterweed (Hymenoxys odorata) on voluntary feed consumption and concentrations of serum constituents were determined in 2 experiments, using 12 lambs each. Feed intake decreased linearly as the bitterweed dose increased. Serum total protein and albumin decreased and urea nitrogen, creatinine, and total bilirubin increased with the increasing bitterweed dose. Serum lactic dehydrogenase, aspartate transaminase, and creatine kinase activities increased at the highest bitterweed dose (0.264% of live body weight/day, air-dry basis). Depression in voluntary feed intake was more sensitive to the bitterweed dose than were serum constituents. This dose-related decrease in ad libitum feed intake provides a useful and less expensive short-term assay for assessing treatments for reducing bitterweed toxicosis, compared with the customary LD50 tests.