[angelaH]

All I can say is that beagles do tend to eat anything,usually without too much trouble. The number of long since dead mice and other creatures I've seen disappear down our beagles throats is amazing! However all our beagles have had bouts of upset stomachs. Some creatures, like voles have a natural poison in them, which may not kill a dog but can make it sick.
Do as your vet suggests for the next few days. Did she/he take any samples for lab.tests? Hope Fin is well again soon.