These Heck Cattle (a famous attempt at recreating aurochs) are in a field just outside Riesa, Saxony, and they are part of a conservation project that attempts to use them to restore European woodland.
This conservation project is actually co-operated by Tierpark Riesa, a small zoo within. the nearby town. Although I regrettably did not have time to visit the Tierpark, while cycling past these cows, they caught my eye and it was very interesting to read about the small collection's involvement in such projects.
Sadly, and strangely, I couldn't find any more information about the zoo's involvement in this and only have some small signs attached to this field, and some more domestics fields nearby, to go off for this information.