Family feud is just a survey of 100 people so it’s not important whether or not they actually slap a cows ass but more how prominent that idea is in people’s heads. I’ve definitely seen it done in the media, mostly cartoons, but I wouldn’t want to do that to a cow in the real world.
I work with kids, it essentially means ass but has a sexualized context to it. Most kids approaching high school realize this and don’t use it as frequently around me, but younger kids seem to think it just means butt. Again this is just my experience and it could vary from place to place