I've never in my life heard of ewe's milk. Could be a regional thing, like avocado on sandwiches. Goat's milk, at least in the US, is in most supermarkets and marketed as a lower-lactose alternative to milk with pretty similar macros.
Again, I think that's mostly a regional thing. Where ever non-poultry/non-red meat is a primary food source (I'm thinking India and the Middle East), those animals will be more commonly thought of as food. Also, way back in the day, Saxon wrote about mutton stew being great for strength.
As far as basic meat and cheese, Vince Gironda called roast beef wrapped around provolone cheese "a bodybuilder's sandwich." Sometimes in a pinch, I'll whip up 3-4 of these kinds of roll-ups as a snack.