Will Molasses or Conditioning Increase Consumption of Spotted Knapweed by Sheep?

Abstract

The spread of the invasive, Eurasian spotted knapweed (Centaurea maculosa Lam.) across the northwestern United States would be reduced if livestock regularly consumed it. We determined if white-face yearling ewes (n = 36) conditioned for 12 days to fresh-cut spotted knapweed, with or without molasses, would increase their use of it during a 5-day field trial and/or a 4-day drylot trial. Ewes were assigned to one of three treatments: ewes not conditioned to spotted knapweed or molasses (NC), ewes conditioned to spotted knapweed (SK), or ewes conditioned to spotted knapweed sprayed with liquid beet molasses (SKM). During conditioning, all groups consumed high amounts of their feed. Nonconditioned ewes (NC) consumed less than ewes conditioned to spotted knapweed (SK, SKM), indicating spotted knapweed did not inhibit initial consumption. In the field, SKM ewes spent more time grazing spotted knapweed and other forbs than SK ewes. In a drylot, time spent eating and intake of spotted knapweed and bromegrass (Bromus inermis Leyss.) varied through time. Conditioning yearling ewes to spotted knapweed, with or without molasses, did not increase consumption of this invasive plant, possibly because sheep inherently graze spotted knapweed only to a certain extent, or we did not use enough spotted knapweed during conditioning.