I cannot create any new saves. Still, no new games will launch after the reinstall.

Grass is my go-to option as it's available everywhere and can be fed to pretty much any animal. I don't know how much food itself affects the acceptance, but petting the animal and spending time with it definitely works.

Thanks for the feedback! The MP QA team confirmed the issue. The corresponding ticket has been forwarded to the developers team.

Did not fix the issues, slightly made it better but still the same results

The top line sets a list of food for 'cowcalf, line 2 & 3 just set the 'cow' and 'bull' values to the same values as the cowcalf - so any changes made to the cowcalf list will also apply to adult cows. The only other food info I can find seems to relate to animals eating from a trough.