Unless the heifers are show heifers, I'd just let them fall off on their own (they will out grow them). I have removed them by putting a cherrio band around the base of large onces. People have posted other methods - squeezing with a pliers, I think. Do a search on warts, I'll bet there are many many posts on this subject.
As Dun says in the second post of the link I posted:
"Squeeze/crush one till it bleeds with a pair of pliars or cut it off and feed it to the heifer, or eat it yourself or feed it to the dog. They all work equally as well since the tearing of the wart is what causes the system to overcome the virus that causes them. If there are different kinds you will want to crush the other types also.
A virus that some get, others don't. We had warts for a few yrs in a row, worked on some animals - haven't seen warts for the last 5 yrs that I can remember (I also don't pay them much attention either). I've never heard anyone talk about why some get it & others don't but then again some more cattle board searching might provide that answer as well.