According to Dominique Zardi in his biography, the cattle massacre with a jeep was of course fake, but the driver Zardi actually hit a cow who later died. Jean Gabin, who was himself a cattle baron in true life, was sad about this event because the dead cow was about to bring low.
Jean Gabin's character name is Maroyeur - or Maroilleur, the same character name that Jean Louis Trintignant has in Le Train, another Pierre Granier Deferre's film, made three years later.