An early alert system and a related method for livestock disease detection are disclosed. In one embodiment of the invention, an activity measurement zone (AMZ) is defined near an incentive device (e.g. food or water dispensing system) with an RFID tag reader, and an animal's entrance into or out of 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 a period of time, then a user of the alert system is informed of a potential health problem with the animal and may also be encouraged to inspect the animal in person for further determination of its current health and potential medical issues.