Supporting rotational grazing systems with virtual fencing: paddock transitions, beef heifer performance, and stress response

Animal welfare is integral to sustainable livestock production, and pasture access for cattle is known to enhance welfare. Despite positive welfare impacts, high labour requirements hinder the adoption of sustainable grazing practices such as rotational stocking management. Virtual fencing (VF) is an innovative technology for simplified, less laborious grazing management and remote animal monitoring, potentially facilitating the expansion of sustainable livestock production. VF uses Global Navigation Satellite System technology, wireless communication, and stimuli (auditory and electrical) to manage livestock movements and contain animals without physical barriers. Training animals to associate the auditory cue with the subsequent aversive stimulus enables effective livestock containment without physical barriers. While previous studies have largely dispelled concerns about adverse effects on cattle behaviour associated with the use of VF collars, there is limited knowledge regarding the impacts on animal physiology, particularly in rotational stocking systems. Addressing this knowledge gap, this study investigated differences in diet digestibility, livestock performance, and stress response of beef heifers on pastures using a VF compared to a physical electric fence. The study was conducted over 8 weeks, subdivided into two grazing cycles, with 32 heifers in four groups. Each experimental pasture was subdivided into four paddocks. The study monitored the interaction with the VF by analysing the temporal development of the ratio of auditory and electrical cues (success ratio and confidence ratio) emitted by the collars. Additionally, the grassland herbage quality, BW gain, and concentrations of faecal cortisol metabolites (FCMs) were assessed, as well as the time required for animals to cross into a new paddock. VF success ratios increased in the second grazing cycle, reflecting enhanced adaptation over time. Similarly, the reduction in time taken to cross into new paddocks in the VF groups indicated that animals learned to interact with the VF and rely on the auditory cues for directing movements. The absence of a significant effect of the fencing system on FCMs suggested that stress was unrelated to the VF technology. Further, animal performance was not affected as indicated by similar BW gains under both fencing systems. This study also attempts to establish a benchmark threshold for successful responses to the auditory cues, allowing comparative evaluation of VF systems. Overall, under rotational grazing, VF did not adversely impact animal welfare or performance compared to physical fencing, opening avenues for further exploration of VF technology in diverse grazing conditions.