Please be informed before you use coffee grounds in a chick brooder that coffee has caffeine in it, even spent grounds. Caffeine is very toxic to chicks if they consume it. No need for a necropsy to conclude that coffee grounds equals toxic substance equals toxic poisoning if chicks consume it...
Caffeine in coffee grounds are toxic to chickens of any age, but especially to baby chicks, since they are more likely to eat them. That chick died from being constipated by eating the grounds. It's also possible, though unknown, it also was experiencing a toxic reaction.
Our conclusion was to...