Where we live, the farmer pays the landowner to graze his cattle on their land.
So I'd be interested to know why it's the other way around to have sheep graze your solar farm.
Isn't the benefit of animals that they are self-managing, that they can identify the sections that need grazing the most, and that they can even self-replicate without human involvement?
Why not just put up some predator fences and then let them do their own thing?