Australian scientists found out how sick sheep heal themselves: they eat things that make them feel better, and they learn it from their moms!
Sheep, he says, are smarter than we think. "There is something called nutritional wisdom and it means that sheep, like other animals,have the capacity to make a choice," he says. ...
“It could be that sheep need certain medicinal paddocks where we take them to self-medicate ... or it could be that they need ongoing low-level intakes of certain plants to keep parasites at bay,” he says.
http://www.sciencewa.net.au/science_archive.asp?pg=30&NID=712