Acquiring and collecting data from a subject animal. A system includes a passive data acquisition device associable with a subject animal including: a sensor, a radio frequency identification (RFID) transponder, and a magnet separate form the transponder. The system also includes a transceiver operable to activate the data acquisition device and to receive and demodulate an RFID telegram from the data acquisition device sent in response to the activation. The transceiver includes an activation antenna configured to encompass areas of substantially equal and substantially opposite flux and a receive antenna configured symmetrically along an axis of symmetry of the activation antenna. The RFID telegram from the data acquisition device to the transceiver comprises an ISO 11784-compliant identification code containing sensor data in the reserved field of the code. In another embodiment, the RFID telegram comprises a modified ISO 11785 telegram.