Trying to figure out why first calf heifer could be three months late and still not showing in sack. She was on schedule with first calf. She was vaccinated with bovi-shield gold last spring before turn out with bull who was also vaccinated. Bull was 2.5 yrs at turn out and they have been running together since. Bull got the other two cows bred at turn out, one was also a first calf heifer (yes it is small herd). Is this not that far behind for a first calf heifer or something else maybe? Thanks for help.