I’ve done it before, peanut butter grains and flower. I had a small dog then and he was hot or miss with it. I have big dogs now and they’d probably love it. On another note, I have 4 chickens who destroyed the cooled down wet grains
I'd imagine chickens, pigs, sheep and other such critters would be joyful over spent grains. Hops are not good for dogs. Some dogs show some allergies to grains, hence the "grain free" diets on many commercial dog foods. Our local possums seem to really appreciate my brew day.