Abstract: An early alert system and a method for livestock disease detection are disclosed. An activity measurement zone (AMZ) is defined near an incentive device (e.g. a livestock feeder) with an RFID tag reader and a uniquely-designed feedlot fence crossbar-embedded RFID antenna, which amplifies multiple signal wavelengths in a single dipole antenna. The early alert system is configured to detect and count an animal's access into the AMZ with an RFID tag attached to the animal. If the animals' activity relative to the AMZ drops to an alarmingly low level (e.g. dropping below an alert trigger point) over time, then a user of the early alert system is informed of a potential health problem of the animal and may also be encouraged to inspect the animal in person for further determination of its current health and potential medical issues.