I just bought a bred heifer from a large Kansas herd. In the catalog they had "bred AI to bull XYZ on April XX, Pasture Exposed to bull ABC from May YY to June ZZ" or something to that effect.  Their preg check prior to their sale indicate the heifer was probably bred by the cleanup bull. 

But the only way you know for sure is to see when the calf is born and back check 283 days and see which bull it was. The preg check was in September and seems to me it could have a good deal of variance.

This would tend to indicate one sync and AI then a month or so later they put them in with the cleanup bull. They probably give them all a shot, line up at the chute for AI and if it does not take it is the cleanup bull.

It will be interesting to see when this one actually calves.

Jim at Dawn