Yes you can feed tatties to your cattle as a supplement to there normal feed. I think you could start of with smallish amounts and build it up to be no more then a certain % which I don't know. Google! I remember as a boy seeing the dairy farmer my father worked for getting lorry loads of tatties which had blue dye sprayed on them so they could not be resold to the general public, the farmer had a turnip slicer thingy and the they went through that. O and we used the tatties as the dye was only on the outside, they were great.