June 8, 2007
June 8, 2007 - Sheep lazily graze in a vineyard, munching on weeds growing between the vines at the University of California's (UC) Hopland Research and Extension Center near Ukiah.
Sheep have been used by farmers for centuries to control unwanted vegetation, but there was always a tradeoff. In addition to keeping down weeds, unknowing sheep would snack on the crop itself. So UC Cooperative Extension is trying to give the animals an education.
"We have a project to train sheep to have an aversion to grape leaves," said Morgan Doran, Solano County livestock advisor and leader of the research project. "If sheep avoid grapes, they can graze the floor of a vineyard, providing farmers an alternative to using herbicides and mowing."
Based on extensive research on animal behavior, sheep that have never experienced grape leaves are allowed to eat their fill of the leaves. They are then administered a small dose of lithium chloride, a harmless medicine that creates the sensation of an upset stomach.
"The sheep experience a brief period of malaise," Doran said. "They recover quickly, but they don't seem to forget, even after nine months."
Initial field observations of trained sheep show they don't like immature grapes or grape leaves, while their untrained counterparts do.
The sheep training research has many potential benefits for grape producers and sheep herd managers.
"In very wet years, farmers may not be able to get tractors into the vineyard to mow or apply herbicides," Doran said. "The sheep can easily get in and clear the vegetation regardless of mud and rain."
In dry years, vineyards provide an additional food source for sheep.
"There is a tremendous amount of feed growing on the floor of the vineyard, so it gives a sheep producer an alternative feed source when traditional feed sources on the range may be low," Doran said. Reprinted in part from UC Agriculture and Natural Resources