Pre-Exposure to an Electrical Stimulus Primes Associative Pairing of Audio and Electrical Stimuli for Dairy Heifers in a Virtual Fencing Feed Attractant Trial

SIMPLE SUMMARY: Virtual fencing may soon provide an alternative to electric fencing in livestock production systems. In virtual fencing systems, a collar is worn by each animal and emits an audio cue when the animal approaches a virtual boundary that has been set via a Global Positioning System (GPS). An electrical stimulus is delivered by the collar if the animal continues to walk forward, but not if they stop or turn. Over time, the animal increasingly responds to the audio cue alone. A better understanding of factors that influence learning of the association between audio and electrical stimuli may ensure all animals adapt in systems that utilise virtual fencing. Dairy heifers were reared with or without exposure to electric fencing. Heifers with experience of electric fencing showed more rapid learning of the association between audio and electrical stimuli. There were differences between heifers in the speed of associative learning, perhaps due to individual differences in the significance of the audio cue, the aversive nature of the electrical stimulus, or the animal’s motivation to feed. Ethically acceptable virtual fencing requires that all animals learn quickly how to interact with the technology. The technology and training protocols may require continual refinement to account for individual differences in learning. ABSTRACT: This experiment examined whether pre-exposure to an electrical stimulus from electric fencing attenuates associative pairing of audio and electrical stimuli in dairy heifers. Two treatments were applied to 30 weaned heifers naive to electric fencing. Heifers in the ‘electric-fence’ treatment were exposed to an electrified perimeter fence and two periods of strip-grazing using electrified poly-wire. Control heifers remained naïve to electric fencing. The pairing of audio and electrical stimuli was assessed in a feed attractant trial using manually controlled training collars. Heifers received an audio stimulus (2 s; 84 dB) when they breached a virtual fence after which a short electrical stimulus (0.5 s; 120 mW) was administered if they continued to move forward. If the animal stopped moving forward no further stimuli were applied. By the third training session, electric-fence heifers received a lower proportion of electrical stimuli than control heifers (p = 0.03). The more exploratory interactions a heifer had with the electric fence, the lower the proportion of electrical stimuli she received during training (r(s) = −0.77, p = 0.002). We conclude that experience with electrical fencing enhanced the salience of the electrical stimulus delivered by manual collars used for virtual fence training.