Abstract: A bolus for administration to a ruminant animal and for retention in the rumen or reticulum of the animal, the bolus having an electronic identification device housed therein with an identification code encoded in the electronic device, and a permanent visual representation of the identification code on and/or within the bolus.

Abstract: A tag, particularly an ear tag for marking animals such as cattle which have passed an official test, comprises a strip formed into two limbs and a hollow rivet, preferably of brass, perpendicular to one of the limbs, the rivet comprising a stock portion which may be frusto-conical or cylindrical surmounted by a narrower neck portion of reduced wall thickness surmounted by an enlarged head portion preferably in the form of a cylindrical punch having a sharp cutting edge. The wall thickness is at a minimum adjacent a shoulder which forms the transition from the stock portion to the neck portion. There is a receiver hole in the other limb of the strip to receive the rivet head. As the tag is being closed, the head punches a hole in the animal's flesh, and passes through the receiver hole after which the head is splayed outwardly. A spring clip may be secured over the receiver hole or the metal of the strip around the receiver hole may be hardened e.g. by stamping.