I know 40-45# bow is NOT ideal, but most western states allow elk hunting with bows of 35-40# minimum draw weights OR LESS.
For those who have killed elk with a 40-45# bow please post.
Here in Idaho the absolute minimum draw weight at 28" for any big game is 40 lbs. Which means if you have a draw less than 28" you need to be shooting a bow of at least 43 to 45 lbs. @ 28".
In this state, big game includes deer, elk, mountain lion, pronghorn, bear, wolf, bighorn sheep, mountain goat, and moose.
You're probably not going to see many, if any, harvest pics of elk or moose with such a low poundage bow. I personally don't know anyone who hunts elk with less than 50 lbs. at their draw weight. It's usually much more.