When the pandemic hit, and production was halted for nine months, Tatum and the trainers got ample time to work with each dog to get them ready for the movie. The result was a powerful bonding experience and ended with three of the trainers deciding to adopt the dogs they worked with.
At the end credits the movie details "In Memory of Lulu". This is in tribute to Tatum's late dog Lulu, a catahoula pittie mix. This movie is in celebration of his last road trip with his beloved dog Lulu before she passed due to cancer.
The dog who appears the most in the movie is Britta, who now lives with her trainer in Hamilton, Montana. Britta is in 80% of the movie.
There are actually three different dogs who played Lulu. Their names are Britta, Lana 5, and Zuza, and though they look similar to German Shepherds, they're actually Belgian Malinois, a breed well suited to police or military work. The production team got them from a kennel in Amsterdam that trains dogs for military service.