Abstract: The invention relates to an isotopic identification method making it possible, where appropriate, to link a livestock animal or animal product to a specific farm, or a plant or a plant product to a farm, by analyzing the concentration of ratios or stable isotopes, and comparing with isotopic codes previously generated in a unique fashion for a set of frames. The invention also relates to a method which makes it possible to impose a unique code on the animals of a farm or on the plants of a farm, a computer making it possible to store the unique codes generated in memory, to generate unique codes for new farms and to perform comparisons.