I try to take a couple horses up into the high country at least once a week and keep them in good shape. I live at 7500’ and we go to about 10,000’ Come hunting and packing season they are good to go. It sure makes it easier when your horses are in shape and used to being in the high rough country.
Yeah usually about 40-70 burro/runner pairs. No classes or distinction between male or female runners/burros or size of burro. Straight up best team wins. You have to have a pack saddle, pan, pick,shovel that must weigh at least 33 lbs (minis are exempted from the weight requirement). There are a few good YouTube videos on it.