Yes, it's so useful that it could be mentioned on the synopsis. However, I disagree on using obscures sub genres in a work you intend to publish. The whole point of classifying a work is to get people to recognize the kind of story at first glance; if you use something obscure you're not only doing the exact opposite but creating an opportunity for potential readers turn down your work.
If you don't care about them and don't make the task of evaluating if it's worth reading they won't have reasons to care about your work either.
I wasn't necessarily talking about the synopsis, but certainly you can word it in a way that introduces people to your genre-mashing. It would depend on how clever you are and whether you think "cattlepunk" sounds cool enough to use. To me, cattlepunk sounds like something that was only cool the first time somebody said it.