Cow tipping-yay or nay?

It depends on what you mean. If you are talking about sneaking into someone's pasture at night to tip over sleeping cows, then no. Cows don't sleep standing up. At least not full REM sleep. Cows can "doze off" a bit while still on their feet (which probably aided in the myth), but even if you sneaked up on one doing so, they'd arose the moment you touched them. Take it from someone with experience in the matter, getting a cow to go anywhere( if it doesn't want to*), let alone having it fall over, by pushing it is a lost cause.

*Now if you have milk cow used to being handled, you can get them to shift position by giving them a shove in the right direction, but this is more of them taking signals from you as what you want them to do.