Compost bin or dig it in is best option. Leaving it in a pile is asking for issues. It will also start stinking and attracting animals. Haven't personallyhad issues with animals but funky mould bad smells etc. Now it all gets composted or dig in or sone is taken for spent grain dog biscuits.
Uses for spent grain are listed in at least 2 threads under 'spent grain'. Interesting solutions sometimes.
My chooks love it, they get ~7kgs every two to three weeks (I brew double batches) between the 9 hens, they really go for it if it's still warm then it's a total free for all, if I leave it till it's cold then they're not as interested.....
So it's never in a pile long enough for those things to get a foot hold!