I've got horese and use them less and less on elk hunts. Sure they are nice for that one day of packing out meat. But they sure require a lot of babysitting the rest of the time.
There are so many roads/trails on the Manti, using them to get around will not be the most effective way. An ATV and boots will be your best bet.
Sure, you feed them all year, and want to use them. But, the reality is they're probably not worth the hassel on what will probably be you only shot at hunting UT elk. Put the focus on the hunt, not the potential pack out.
You might have one hellish day of packing meat on your back, but it just adds to the adventure.