The shelter, however, will not switch to sodium pentobarbital, Mitchell said. "Unless you have an actual veterinarian on site to administer and supervise the process, in my mind euthanization by injection is inhumane."
Jodi Buckman, director of animal-protection services for the American Humane Association, said training shelter workers on proper euthanasia techniques is important.
"We want them to be the most humane people in our communities, because they are taking care of the homeless animals that no one else has taken responsibility for," she said.
Currently four states—Colorado, Georgia, Indiana, and Nebraska—require special training for workers who use lethal injection to euthanize animals.
Animal welfare advocates say euthanasia rates are on the decline. Experts attribute the decline in large part to aggressive spay and neuter programs initiated by shelters and humane societies.