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. food or water dispensing system) with an RFID tag reader and/or an RFID antenna. An animal's access into the AMZ is tracked and counted 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 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. The early alert system may be powered by hybrid alternative energy sources for rural or remote areas, which may have inconvenient or expensive access to conventional electrical power lines.