Golden retrievers key to lifetime dog cancer study - Article Photos 3/5

This 2012 photo provided by Colorado State University, shows a golden retriever, Louie Mesinger, taking a rest after swimming and diving in the summer at Holland Lake, in Mont. When Jay Mesinger heard about a dog cancer study seeking purebred golden retriever puppies to track their health for life, he immediately signed up 2-year-old Louie. He and his wife know firsthand the toll that canine cancer can take: Louie is their fourth golden retriever. (AP Photo/Colorado State University/Josh Mesinger)