Butcher won't collect dead animals.

[Squashie]

A few animals in my pasture died but no one is collecting them. Is that expected?

[LaChouette]

Stray animals that died from anything other than slaughtering won't be butchered, as far as I know.

[Sinclair]

This is finnicky, and has always been. Sometimes you can force a dead animal to be butchered by building a butcher shop nearby and then manually adding a 'Butcher a dead animal' job to it. However, this won't work if the corpse has already started to decay, or is too far away from the workshop. Sometimes, you will just get an error about no suitable animal.

[morbious37]

I had a hard time with this, you have to go into the animal management menu and mark them to be slaughtered, and the butcher has to be next to the pasture (40 squares I read). If it dies on its own I think it won't get used, like LaChouette said.