Foraging for livestock?

Anyone out there supplement livestock feed with forage? What do you harvest/store for them?

I have chickens, goats, a pig, and I'm expanding to sheep soon. What sort of grub and treats can I harvest or store up for each? I'm lucky enough to live in an area with miles of grass/hay free for the taking, and wondered if it would be difficult to haul it on my lonesome.

I have a friend who is shoveling up dead periodical cicadas and drying them for winter right now. His chickens act like they're candy!

My chickens go nuts over foxtail seedheads, as well as greens like lambsquarters. They'll do their own foraging for clover and stuff.
(Not free-range, but they're allowed supervised outings when the weather is good. Too many predators for them to be out unattended.)

I've got one hen who gets really excited if she sees me digging, because she knows I'll toss her any grubs or worms that I find.