Validation of an active RFID-based system to detect pigs housed in pens

Experiments conducted in different breeding conditions have shown that active RFID systems based on the use of position markers can detect the presence of animals equipped with active tags within areas bounded by induction loops. However, from these experiences, a number of disadvantages, mainly attributable to the cost of the position markers and the complexity of the installation of the induction loops in the breeding environment, have emerged. This paper describes a configuration of an active RFID system alternative to that making use of position markers for the automatic detection of tags. The automatic detection system proposed in this study employed a specifically implemented algorithm based on the concept of reference tags, and the same hardware utilized in previous experiments, excluding position markers and induction loops. The automatic detection system was initially tested in the laboratory and then applied to a group of pigs housed in a pen consisting of a built and completely roofed resting area (indoor area) and an enclosed open-air area (outdoor area). The laboratory tests revealed a localization error almost equal to that obtained in other similar studies which utilized a greater number of reference tags than that used in this research. The field trial carried out in this study demonstrated that it is possible to detect the pigs resting in the indoor area by avoiding the cost of the position markers and the complexity of the induction loops installation. High error rates were observed in the outdoor area mainly due to the building characteristics of the fence.