I think you Aussies are way ahead of us in the US in terms of tree fodder. Here agriculture is ruled by the universities who only teach what big ag tells them to. No innovation if there's no money for big ag in it - or am I being too cynical?
I got some willow and hybrid poplar cuttings and if they work out as fodder I'll be passing them around to
local farmers to incorporate as a fail-safe against the droughts that are becoming more and more common here, or so it seems. What happened last summer was just horrible - animals left to starve until they were too weak to move and had to be shot in the fields because
hay became either too expensive or just not available. There's no good system here to move hay from where there's a surplus to where people desperately need it. And that would just spread the losses to the non-drought areas as the prices of hay in the whole country would then skyrocket.
But I think we've been a victim of our success - grass usually grows so well here in so much of the USA that we've never felt the need to look at alternatives. And, really, in the great plains, grass is the most sensible thing to grow, but it probably needs to be the deep-rooted, drought-proof kind and even then the stocking needs to be managed so it isn't all consumed during droughts.
That said, the fur trade here really changed the landscape more than people may realize. Beavers used to dam up creeks and send
water on these jagged paths so there was a lot more available for
trees in the plains. Now the beavers have been reduced to a very small number, the streams run straight, and mostly are used up for irrigation of crops not adapted to the normal amount of rainfall in the area (like green lawns).