Abstract: The need to positively identify ownership of cattle is well recognized and understood and has given rise to the practice of hot iron branding. This method, however, has proven less than satisfactory and a variety of alternate methods have been explored with varying degrees of success. One such method utilizes a transponder encased in a pellet and deposited in the cow's reticulum where it remains until slaughter. This method, lacking an active source of electrical energy, is severely limited in its range of data transmission and in addition is unable to power other sensors for monitoring various bodily functions such as temperature. The present invention discloses a method and apparatus which overcomes these shortcomings by providing an active source of electrical power within the reticulum of the animal and which comprises an elongate, cylindrical zinc tube closed at one end and having an integral dividing wall with an elongate solid carbon rod extending coaxially therethrough.