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Narrator: For centuries, farmers have used sheep to control unwanted vegetation. The problem has been that in addition to keeping down the weeds, unknowing sheep would snack on the crop itself. So, University of California farm advisors have decided to give the animals an education.

Morgan Doran- Livestock Advisor/study leader, UC Cooperative Extension:

We have a project here to train sheep to have an aversion to grape leaves, so that the sheep can graze the vegetation on the floor of the vineyard as an alternative to using herbicides, tillage and moving, could potentially reduce fuel costs, reduce soil compaction caused by tractors. And it’s a practice that’s been adopted by some vineyards in Sonoma and Napa counties already. What we do is we take sheep who have never experienced grape leaves before, never eaten grape leaves before, so it’s a novel food for them. And we let them eat grape leaves and once they consumed enough and have a full belly of grape leaves, we give them a small dose of lithium chloride and it creates a mildly upset stomach to create this negative association or this negative biochemical feedback that tells them, this is something I ate and it’s a new food and it’s making me feel a little bad.

Narrator: This simple method saves grapevines.

Morgan Doran (V/O): This is what happens when we have untrained sheep exposed to grave vines. You see a lot of damage on this. All these were stems this high – about 10-12 inches long – and now they’re only four inches long, maybe less than that. We see almost every stem on this vine has suffered some damage by the sheep, as well as many butts here. So, this is what you can expect with untrained sheep in a vineyard. Creating this aversion in the sheep, it really broadens a window when sheep can graze a vineyard without damaging those grapevines and the fruit. We do not see any fruit on these vines at all, whereas some of the vines in the treatments were the averted sheep, or the trained sheep who are grazing, are already bearing some fruit.

Morgan Doran (O/C): So, this project – if the sheep can be successfully used for managing the vineyard floor vegetation – can provide benefits for both vineyard managers, primarily those involved with organic and biodynamic grape production that also has a benefit for sheep producers because they can provide a service to the vineyard, vineyard managers, by bringing in sheep to graze the vegetation and therefore creating a form of income for sheep producers who have traditionally had land markets that oscillate up and down a bit. This can provide a more secure form of income for them.

Narrator: For Science Today, I’m Larissa Branin.

Trained sheep

6.2007

A bucolic scene that harkens back to antiquity is being played out at the University of California Hopland Research and Extension Center, south of Ukiah. Sheep lazily graze in a vineyard, munching on weeds growing between the vines.

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.”

To change the animals’ diet preference, the researchers consulted with noted animal behaviorist Fred Provenza of Utah State University.

“We often see livestock and wildlife as eating machines and don’t understand that an animal’s history influences its diet and habitat preferences,” Provenza said.

Provenza said animals learn from social interactions with their mothers, peers and people; feedback from nutrients and toxins in plants; and interactions with their physical environment, including location of water and predators.

“Behavioral principles can provide solutions to problems faced by producers and land managers,” he said.

Based on Provenza’s extensive research on animal behavior, the UC Cooperative Extension researchers allowed sheep to eat their fill of grape leaves, then administered a small dose of lithium chloride, a harmless medicine that creates the sensation of tummy trouble.

“The sheep experience a brief period of malaise,” Doran said. “They recover quickly, but they don’t seem to forget, even after nine months.”

Field observations are promising

Initial field observations of trained sheep show they don’t like immature grapes or grape leaves, while their untrained counterparts do. In the Hopland vineyard, Doran pointed to a grapevine with very little new growth.

“This vine was exposed to sheep that hadn’t been trained,” Doran said. “We see a lot of damage on this. Most of the vine shoots were 10 or 12 inches high. Now they’re gone.”

In another part of the vineyard, sheep that received training ignored the grape leaves and emerging fruit, concentrating instead on eating weeds.

The sheep training research has many potential benefits for grape producers and sheep herd managers. Sheep weed control fits guidelines for organic production, in which no artificial pesticides or fertilizers are used, and biodynamic production, a system that builds on the organic philosophy with additional natural and holistic management practices. Conventional farmers may also want to look into the use of trained sheep for vegetation management.

“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. The producer can then conserve food for the summer or fall,” Doran said.

The farm advisors working on the project believe their research could have far-ranging implications, including orchard weed management and making use of the space between trees in a young planting to grow livestock feed.

The sheep grape leaf aversion project is funded with a grant from the UC Division of Agriculture and Natural Resources. Farm advisors involved, in addition to Doran, are Roger Ingram of Placer and Nevada counties, Stephanie Larson of Sonoma County,  John Harper and Glenn McGourty of Mendocino County and Ed Weber of Napa County, and Associate Professor Emilio Laca and CE Specialist Mel George of UC Davis.