Seth Sachson, executive director of the Aspen Animal Shelter and the Aspen Boarding Kennel, mushes toward the finish line Sunday during the seventh annual Grand Mesa Challenge sled dog races. While many of the 35 or so mushers competing over the weekend raced behind teams of Siberian or Alaskan huskies, Sachson’s team is composed of mixed-breed dogs he has rescued and adopted from the animal shelter.