Unique and secure identification of livestock from birth through to the carcass in the abattoir will become a key feature in many areas of livestock production: disease eradication; quality assurance schemes; pedigree breeding; and producer feedback from abattoirs. There have been many attempts at adapting traditional methods of animal identification to provide a measure of automatic recognition. None has been as successful as the application of radio frequency transponders which transmit a unique code when triggered by a suitable reader.