Effects of common management practices on heart rate of virtually-fenced beef cattle

An experiment was conducted to evaluate the impact of virtual fencing (VF) on heart rates (HR) of trained beef heifers when challenged to remain within known VF boundaries. The study tested how 3 different attractants related to common management practices within the exclusion zone - water, supplement and a feed siren - affect the heifers’ HR as well as their willingness to cross the VF. A group of 3 heifers were equipped with GPS-based VF collars, HR equipment and one with a GoPro, were initially placed in a pen for a 5-min period to stabilize their HR. They were then moved to the trial pen where they interacted with the VF. Following this, a 5-min baseline period was observed. Followed by the test phase, where the heifers were exposed to one of 3 attractants—water, supplement, or a feed siren—for 5 min. This was followed by a 5-min recovery phase. Data was analyzed using R (R Core Team; 2024), HR data with two linear models evaluated via ANOVA and emmeans, while heifers’ VF crossings was evaluated with chi-squared test and pairwise comparisons. Virtual fence crossings were defined as the heifer moving towards the attractant during the test phase, disregarding the VF (despite previously interacting with it and receiving either an auditory or electrical cue). The exclusion zone containing the feed siren led to significantly more heifer crossings over the VF compared to water (P<0.05). The absence of crossing for water suggests reduced enticement, likely due to the winter season or disruptions in the grazing pattern during the trial. Baseline HR significantly influenced HR responses during test and recovery phases (P<0.05), with higher baseline rates correlating to increased HR responses in subsequent phases. No significant differences (P>0.05) in HR were found between attractants, suggesting that physiological responses may be more affected by pre-trial conditions than by the type of attractant itself. These data suggest that attractants such as feed siren entices heifers to cross VF, even when they are trained and aware of it. All heifers would eventually return to the grazing area indicating they were correctly trained. VF does not induce significant physiological stress in beef cattle, as evidenced by HR responses during the test and recovery phases. Instead, pre-trial conditions had a greater impact on subsequent heart rate phases. Further research is needed with a more detailed analysis of HR and HRV, along with additional indicators, to better understand the impact of VF on stress. Overall, VF shows a promise as a useful tool for ranchers in the near future.