In the first weeks of the game, after having repaired the graveyard to a +5 quality level and the bishop has opened the access to the church, your friend the donkey will suddenly stop bringing you new bodies.
He wants his fair share of the booty!
From there, he asks you 5 carrots per new body, deposited in advance in a box near the morgue in packs of 10.
He also wants oil for the wheels of his cart and the latter is easy to obtain, but its location is not obvious to know.
How to get the oil
Just go to the village and continue a little bit by the road to the east.
You will then fall on a NPC named Dig, who sells the oil that the donkey wants for only 30 pieces of copper.
Once he receives the oil and the carrots in his little box, your friend the donkey will resume service and bring you new bodies at the morgue!