That the Farmer is sending the Bull's Cows and Calfs to a better field somewhere.
The farmer very much wants the Bull to be happy and so keeps the deceit alive.
The bull says that this is what he believes is true
This is a case of telling yourself a lie that could be hurting you and your family.
As an allegory perhaps it doesn't need a label since it is obviously fiction. Crows and Bulls don't talk.
The motivation is to not worry and be happy.
The bull hears the truth but misinterprets it as impossible in his direct experience.
The Bull should realize and not forget what the Crow told him. And also figure it must be true.