Mean Dog Blues (1978)

When his friend injures a little girl in a small southern town while driving drunk, country singer Paul agrees to state in court he had been driving. But his lawyer betrays him, and he ends up on a prison farm, sentenced to five years. Prison turns out as a living hell, when Paul not only has to work hard in the heat of the day, but the sadistic foreman uses his prisoners to train his fighting dogs, who he loves more than anyone else, and there seems to be no chance of getting away.