Like last year’s “Buck,” the documentary “Wild Horse, Wild Ride” is saddled with so much pathos that it shouldn’t be able to move; but with a large cast of two- and four-legged characters to share the load, it saunters into our hearts.

The competition, supported by the Federal Bureau of Land Management to find homes for endangered wild horses, pairs trainers with mustangs that have never been touched by human hands. The 100 trainers have 100 days to tame the horses before a riding competition in Fort Worth, Texas. After the contest, the domesticated horses are auctioned to the highest bidder.

The initial interactions are frightening for everyone involved, as the wild horses buck against the corral fences and wary trainers approach them with outstretched hands. Some of the trainers, such as a young woman who teaches engineering, are skittish newcomers. Others, such as a Navajo grandfather from Arizona and a 60-ish couple from Texas, are grizzled veterans of the contest who are giving it a last try. And still others, such as a beatific young Mexican immigrant who lives in Wisconsin and two home-schooled brothers from New Hampshire, represent an almost mystical new approach to interspecies communication.

Despite their diverse backgrounds, almost all of the trainers become emotionally attached to the horses as the animals learn to trust the humans’ commands.