There is still a lot of nutrients in spent grain, lots of fiber and protein is left over. I'd suggest google if you want the particulars, but it's got lots of good stuff left in it. I doubt animals would die of malnutrition from eating it. Hops will make some animals sick, but spent grain...
I've made great bread, you can dry it and grind it into flour, dried works good for bird feed as well. Chickens or just wild birds. Deer love them, as do cows, pigs, horses.