Cow tipping, at least as popularly imagined, does not exist. Drunk young men do not, on any regular basis, sneak into cow pastures and put a hard shoulder into a cow taking a standing snooze, thus tipping the poor animal over.
While in the history of the world there have surely been a few unlucky cows shoved to their side by boozed-up morons, the evidence against cow tipping is immense, and backed up by both farmers and the laws of physics.