Yeah, I don't think Poing had cows, actually, though I remember tons of chickens. For some reason. And I think there was something ruminant, though it wasn't exactly a cow.
Anyway. The site uses frames, so I can't point you right to it, but there is one horse-riding farm (with the little cow-picture, so maybe there are cows, and the English-flag-picture to the side) called the
Spiegler Ranch, near Neu-Ulm, which is quite close to Legoland. If that's not your thing, then you'd best try the Allgäu-Bayerisch Schwaben part of the map, since those will be between Munich and Günzburg (Legoland), and so will make a good halfway stop.
Keep me posted. I'd be interested to hear what you settle on, and how it works out.