A farmer and a son live on a farm.
The farmer is sitting in the kitchen when his son comes in from the barn with a large glass filled with white liquid.
He is so excited because he’s just milked a cow. Then he takes a big drink from the glass.
His father just stares at him. “Son, we don’t have a cow. We have a bull. “
This joke is included in the Black Book of Jokes. You can order it from here.