The only cow in a small town in Alberta stopped giving milk. The people did some research and found they could buy a cow from Saskatchewan for $200.
So they bought the cow from Saskatchewan and the cow was wonderful. It produced lots of milk all of the time, and the people were pleased and very happy. They decided to acquire a bull to mate with the cow and produce more cows like it. They would never have to worry about their milk supply again.
They bought a bull and put it in the pasture with their beloved cow. However, whenever the bull came close to the cow, the cow would move away. No matter what approach the bull tried, the cow would move away from the bull and he could not succeed in his quest.
The people were very upset and decided to ask the local Veterinarian, who was very wise, what to do. They told the vet what was happening. "Whenever the bull approaches our cow, she moves away" they said. "If he approaches from the back, she moves forward. When he approaches her from the front, she backs off. An approach from the side and she walks away to the other side."
The veterinarian thinks about this for a minute and asks, "Did you buy this cow in Saskatchewan?"
The people were dumbfounded, since they had never mentioned where they bought the cow. "You are truly a wise veterinarian," they said. "How did you know we got the cow in Saskatchewan?"
The veterinarian replied, with a distant look in his eye, "My wife is from Saskatchewan."
Hat tip: Frank of Foxxfyrre's Honk'n'Holl'r