I just googled this because I eat a handful of boiled shrimp a couple of times a week and was wondering if I could toss the shells to my pullets (when I get them).
I was thinking it might be a good source of calcium, but nope, they're made from something else, chilatin? Good protein source, but didn't see anything that said they would be harmful to chickens, at least in the amounts I'd be giving them.
Good to know that others do it with no ill effect. I'll offer my girls a treat and see what happens.