Is shot placement is near perfect … then yes 45lbs is enough to kill whitetail, as well as many other big game. I shoot my Hoyt Vectrix at 67lbs when targeting/5-spot … as well as hunting. 67lbs is PLENTLY to kill anything in North America. I took a awesome 10point this year, 32 yard shot, 1/4ing away, and he only went 50 yards max before be expired.
A lot depends on the broadhead used as well. I used Rage Slip Cam Expandables this year (3-blade) and will NEVER use another broadhead. The entry/exit hole (total pass threw) was un-believeable