Effect Of 2,4-D on Hymenoxon Concentration and Toxicity of Bitterweed (Hymenoxys odorata) Force-Fed to Sheep

Abstract

Bitterweed (Hymenoxys odorata) growing at two locations was sprayed with 2,4-D (1.1 kg acid equivalent/ha) during the spring of 1977. Subsequently, plants were collected, dried, and stored when they showed definite signs of herbicide phytotoxicity (epinasty and turgidity). Hymenoxon concentrations were determined on the dried plant material and it was force-fed to penned sheep, in two experiments, to determine the effect of foliar spraying with 2,4-D on bitterweed toxicity. Bitterweed administration decreased voluntary feed intake and increased serum concentrations of urea nitrogen (UN), creatinine (C) and glutamic-oxalacetic transaminase (GOT). Hymenoxon concentrations (air-dry basis) were 2.33 +/- .18% and 1.64 +/- .05%, for unsprayed and 2,4-D sprayed bitterweed, respectively, in Experiment 1 and 1.24 +/- .02% and 1.08 +/- .05%, respectively, in Experiment 2. Spraying bitterweed did not affect feed intake and serum levels of UN, C and GOT and there were not interactions between bitterweed levels and 2,4-D treatments.