First off, I wouldn't mix sheep and goats. Goats need copper; copper is toxic to sheep. I know there's a lot of feed out there that's labelled "sheep and goat," but there's really no such thing. If you feed a goat "sheep and goat" feed, it's going to get copper deficient which can lead you to a whole slew of problems. Immune problems, fertility problems, parasite problems, lameness -- you name it, copper deficiency can play a role in it.
If the goal is to turn grass into meat and you go with goats, I'd go with boers or boer crosses. The crosses may not give quite as much meat as a purebred or fullblood boer, but they're cheaper to buy, more plentiful, and in my experience, they require less doctoring -- especially if you can find an F1 cross where mama and daddy were more or less purebreds of different breeds. And if they're just going to the table.....well, I don't think I'd be terribly concerned about papers anyway. I'd go with crosses, for sure, personally.. That's just me, though.
I've actually read before that nothing eats better than a boer/nubian cross, but I don't eat goat, so I really don't know. What I can tell you is that we've got some near-F1 boer/nubi crosses that are excellent examples of
hybrid vigor . They're healthier and hardier than our purebred stock any day of the week, which makes them MUCH cheaper to own.
Good antibiotics and dewormers aren't cheap, afterall.. Just something to think about.
