You need to make sure the genetics you are using are free of problems. If you use a line that has had a problem bull in the background you will certainly see it rear it's head.
I think the "real" Rito cattle can obviously handle linebreeding much like the Emulation line cattle.
After that you need to be pretty careful as there are problems of function that will cost you.
Traveler - poor feet and small nuts, maybe some white
Lots of Papa cattle are pure and are linebred to begin with.
