A farmer was helping one of his cows give birth, when he noticed his four year old son standing at the fence with wide-eyes, soaking in the whole event.

The man thought to himself, "Great... he's four years old and I'm gonna have to start explaining the birds and bees.  No need to jump the gun - I guess I'll let him ask and then I'll answer."

After everything was over, the man walked over to his son and said, "Well son, do you have any questions?"

"Just one," gasped the still wide-eyed lad.  "How fast was that calf going when he hit that cow