Some pasture is to "good"Quantity always has quality in it if it was grazed properly last time. I would say sheep would be fine, my mate Shane is out to about 100-120 days with sheep (behind a single wire I should add!) and this past couple of years they've sent better than 30% of lambs off the weaning draft, as good as the guys who have 'em licking dirt for a living.
Obviously depends on the sheep.