I have a vague recollection of having seen a movie on T.V. many (many) years ago (early to middle 1960s) about a cruel prison warden who kept these fierce hounds as guard dogs. I recall that the prisoners were mistreated, perhaps they were political prisoners, and, at times tortured, and, perhaps, fed to the dogs. I also recall that their blood was sometimes drained, and, perhaps consumed by the warden (none of this is very clear to me and given the time, none of this would have been explicitly shown). I recall the film had a Mexican or Spanish setting, but this may be my own childish interpretation of the uniforms of the guards (I was a child, and may have misread the setting).
However, the conclusion was something that has frightened me for years, even though it was an off-screen event: the warden, fleeing from some disruption in the prison (perhaps a revolt, I cannot recall), is torn to death by his own dogs. His shrieks and the dogs' howls were quite vivid and terrifying, "blood-curdling" as goes the clichÃ©.
Perhaps this is why I am, to this day, so wary around dogs.
UPDATE: It seems Joe D. (with assistance from Leonard Maltin) has answered his own question with 1958's BLOOD OF THE VAMPIRE...