Cattle
The cow is a species of large, formerly domesticated ungulates originally from the Middle East. After collapse, surviving cows went feral.
#Human relations
People of the Fifth World will sometimes hunt herds of feral cows for meat and make clothing - and sometimes houses - from their skins. More rarely, when specializing in relationship with cows (see below), they may milk them.
#Specialization
A community that specializes in relationship with cows will likely follow the semi-feral herds as they travel, possibly going so far as to burn out fields for them to graze in.
They may have a tradition wherein certain people manage to so closely befriend individual female cows that the cow allow them to milk them. One such tradition may limit only children to this task (maybe young girls, in vague memory of milkmaids), as milk of any kind is generally meant only for babies. Regardless, the consumption of milk or milk products by adults is very rare in the Fifth World. Milking animals, and making butter or cheese from that milk, would make this community fairly unique.
Communities that practice a form of Hinduism are more likely to specialize in relationship with cows, but will never kill them for meat unless their variation on Hinduism has diverged wildly from the religion's historic respect for these creatures.