Our goats like a dessert menu of multiflora rose and grape leaves. If we're pulling down vines from thickets they're right by our knees expectantly. They cooperate/compete while the larger ones use their horns and legs to step on and bring down the fresh saplings for a herd munch. Russian olive seems particularly tasty to them. If the fresh cut branches of mulberry are brought to them or pine boughs, they really move in to feast on them. Leaves of squash and sweet potato vines are really interesting too.
There's some tradition of making silage in small quantities from sweet potato leaves & vines. Great amount of protein and really nice if you're growing organic and scythe & pitch fork them before digging up the potatoes.
This sweet potato topic deserves another thread of its own, I guess.
Dave Jacke & Mark Krawcyzk had a SARE funded research project and they talk about how silvopasture and coppice/pollarding produces much forage value on farms with sheep & goats. List of protein by species:
Their research led to a great book which also talked about how tree forages have been harvested and kept over the last 8,000 years or so. Coppice Agroforestry,...
Plus, the small diameter wood after animals eat the leaves is perfect quick fire fuel for the bake ovens. link to description:
Steve Gabriel offers much tree forage info and great classes. I think he might focus on species: willow, poplar, mulberry, black locust, and there's much discussion of others on his fine blog:
Steve Gabriel webinar replay about
Intro to tree fodder