Old Yeller was a children’s book adapted for the screen by Disney in 1957. The story is about a poor post-civil war family who is very poor. While tending to the livestock one day, the older son (Travis – played by Tommy Kirk) notices a stray dog. He tries to shoo the dog away but the younger son (Arliss – played by Kevin Corcoran) becomes quite attached to the dog. Their mother (Katie – played by Dorothy McGuire) reasons that they could use a good dog around the house. The dog was named “Old Yeller” (yellow) due to his yellowish color. He was played by a mixed breed (yellow lab / mastiff mix) adopted out of the Van Nuys Animal Shelter in Van Nuys, California by trainers Frank and Rudd Weatherwax named “Spike” (he wasn’t credited for the role). Spike also had an uncredited role in the 1957 fantasy-horror film, “The She-Creature”. In the book Old Yeller was a Black Mouth Cur.
Black mouth curs were not uncommon in the earlier USA days (“wild west” days) in the southern USA (Texas, etc.) and could have been chosen as the breed in the book because it was recognized and it was a common hunting companion dog. They can be rather intelligent and do not require a lot of maintenance which would make them a god dog to have during this time by many poorer people. Disney probably changed Old Yeller to the lab mix so people would recognize it in the movie.
Spike’s owners, Frank and Rudd Weathermax, were also credited for being the on-set dog trainers for this film.