Daniela,
i’m not sure what you mean by “worse.” If you had milk that you KNEW was froma treifa cow (say you shechted it right after milking it and found it to be a treifa) then it would be treated a any treif milk and requires 60 to be mevatel.
If you dont know the status of the cow (which presumably is usually the case as when you walk into your local grocery and pick up some milk there is no way you can know what the status of the cow is) The gemara says that rov cows are not treifa. Therfore every living cow can be assumed to be a member of that rov and all milk is Kosher.
This is the halacha as codified and according to most poskim is equally applicable today.