Dr. Freud would have called this effort "sibling rivalry"

The result of their experiments to re-breed the aurochs was according to the Heck brothers quickly achieved and had a strong resemblance to the real aurochs. Lutz released his Heck cattle into the wild(below) in large nature areas in Germany and Poland, but Heinz kept his Heck cattle(above) exclusively in zoos and small game parks. Most likely the Heck cattle of Lutz have not survived World War II, and do only the Heck cattle of Heinz remain today. After the war, individual breeders have bred the Heck cattle to their own (often wrong) insight. Today, Heck cattle can be found in many places, like zoos and nature parks.
Relatively fast after the creation of Heck cattle there came criticism to as well the execution as the result of the re-breeding experiment. The criticism addressed especially on the image on how the aurochs looked like, that the brothers Heck had formed themselves. This image was created by a mixture of truth and mostly phantasy. There was even a difference of opinion between the brothers over how the aurochs looked like. Furthermore there was criticism on the way they bred and selected and on the speed on which they reached their end result. Heinz worked at most 12 years on his experiment, and Lutz only at most 11 years. The selection criteria were vague and broad, and there was no good administration kept of the crossings that had been made. The re-breeding experiment of Lutz and Heinz Heck is characterized by an incompetent and untransparent way of working.
When we now compare the Heck cattle and the real aurochs, we see that there is little similarity between the two. Only the colour of the fur of some Heck cattle is similar, but there are also many Heck cattle with a wrong fur colour. This is caused by the recessive genetic characteristics which still exist in Heck cattle and originated from the used domesticated European cattle breeds. Other characteristics, like the shape of the horns and body size, do not resemble the real aurochs.