Hi,
I kept three lambs in an acre orchard last year and then sent them on for slaughter in the autumn. The lambs and the orchard grass were fine, but not sure how it would have faired after staying out on it all winter. Think I would have needed more grass for a regular rotation.
Like I said, if you just want them for slaughter then you would be fine, but keeping all year round would need need more grass.
xx