Actually, eating us makes significantly more sense. Any alien civilization with the capability to travel interstellar distances is unlikely to have any particular need of our terrestrial resources (including labor) when there's plenty of raw material orbiting any given star including our own that's much less trouble to get at.

However one can envision "alien meat", having required light-years of travel (and corresponding years of time) to acquire, as a status-signaling delicacy. Hell, it might even be technically illegal, which is why it's so small scale.

Or all of those — use every part of the cow.