Challenges in the design of a GNSS ear tag for feedlot cattle

A Global Navigation Satellite System (GNSS) based ear tag was designed developed and tested for use on cattle in feedlots. Previous research by others has primarily used GNSS collars; however the widespread use of a Position, Velocity and Time (PVT) system onboard cattle in the feedlot requires a less obtrusive system with easier application and lower costs. The ear tag is already widely used for cattle identification and it seemed a natural extension to develop a PVT solution around it. This paper describes the development of one of the first GNSS ear tags for cattle. An alpha GNSS ear tag weighting 227 g was developed in 2004 with a run-time of 1 week while reporting animal position and velocity every minute in real-time using a low-power proprietary wireless link. Feedlot testing showed that a 227 g tag could not be tolerated by the cattle for prolonged periods. In 2005 a 125 g beta ear tag was designed and tested with a run-time of 4 days. While the beta tag's run-time was below expectations due to problems with the battery and power regulator, it did show that a GNSS ear tag could be worn by cattle for periods of up to 4 weeks. Described is the alpha and beta tag design along with the challenges faced putting these systems together and getting them to work on cattle in the feedlot. Future research may benefit from not having to repeat lessons learned during our development of the first GNSS based cattle ear tags. (C) 2009 Elsevier B.V. All rights reserved.