I think that a combination like 75% Sayaguesa and 25% Watussi or a good F2 of both breeds might resemble the aurochs quite satisfyingly. Just imagine Sayaguesa with large, thick horns - it might be comparably close to the goal already; not perfect immediately, of course.
Taking such individuals (either 75% Sayaguesa 25% Watussi or good F2) and crossing them large, well-built F2 Sayaguesa x Chianina has the potential to result in quite superior animals in my opinion.
Thus, I am also happy to read that the beautiful Chianina bull Bruno has been moved to Bielefeld to cover the three other Sayaguesa cows for this year. That means finally some more Sayaguesa x Chianina crosses - I am so much looking forward to F2 of this combination. When Bruno is back from his "job", he is going to cover at least one of the Watussi cows.
It is very enjoyable to see how the Auerrindprojekt is getting going.