Prussic acid, cyanide, or hydrocyanic acid are all terms relating to the same toxic substance. Hydrogen cyanide was first isolated from a blue dye (Prussian blue) and because of its acidic nature it became known by the common name “prussic acid.” Cyanide is one of the most rapidly acting toxins that affect cattle.
Arnold, Michelle; Gaskill, Cynthia; Smith, S. Ray; and Lacefield, Garry D., "Cyanide Poisoning in Ruminants" (2014). Agriculture and Natural Resources Publications. Paper 168.