You my also be interested in details:
Short on aurochs-cows ancestry:
Fossil DNA tell us that aurochs were very variable species. All cattle in Europe are descendants of Near Eastern cattle brought by Neolithic farmers. Contribution of European aurochs genes exists, but is almost nill and not present in any one race (hecks or another) more than other.
Short on aurochs-heck apperence:
Mr van Vuure himself tells that Spanish fighting cattle is cattle breed most closely similar to aurochs visually. Hecks have only big horns and usually color dimorphism (bulls black with white back-stripe, cows brown, calves rufous-brown). Spanish cattle have more auroch characteristics: horns are pointing forwards, not up, and come close togerher (not U-shaped), long legs, long muzzle, small ears. The extinct aurochs had also even bigger horns, and giant size (ca. 190cm in males) matched by few modern giant cattle breeds. So, don't imagine yourself aurochs like these heck cows from Netherlands on the pic above, with widely spreading horns!