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

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 (rs = −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.

The Effects of Dairy Heifer Age at Training on Rate of Learning and Retention of Learning in a Virtual Fencing Feed Attractant Trial

“…The electronic collars used to remotely deliver the audio cues and electrical stimuli were the same as those used by Verdon et al (2020). The collars were based on those used for dog training (ET300 Mini-educator, E-Collar Technologies, Garrett, IN, USA), fitted into a custom casing (MooMonitor + , Dairymaster Inc., Kerney, Ireland) and enabled an operator to manually deliver audio or electrical stimuli through a remote control device.…”

“…The new arena also positioned the post-test holding pen in front of training paddock. This second test area is the same as that described by Verdon et al (2020) and was utilized for all training in the present experiment excluding the initial training of the 6M heifers.…”

“…Four sessions of training of the pairing of the audio and electrical stimuli with activated collars were held over 2 days immediately following the habituation period. This number of sessions was chosen because previous research found that from the fourth training sessions heifers could be categorized as consistently avoiding interacting with the virtual fence or consistently tolerating the electrical stimuli to reach the feed attractant (Verdon et al, 2020). Individual heifers were introduced to the test arenas during each training session.…”

“…The following procedures determined the application of the audio and electrical stimuli by the researcher, as utilized by Verdon et al (2020). Based on the researcher's visual estimation, the audio stimulus was applied for 2 s as the heifer entered the exclusion zone.…”

“…A second explanation for the faster rate of learning observed in the 22-month old heifers is that their older age had provided greater opportunities for experiences that improve associative learning or other cognitive skills. For example, Verdon et al (2020) found that experience with electric fencing resulted in more rapid associative pairing of audio and electrical stimuli in dairy heifers compared to those that had no experience with electric fencing, and the more interactions a heifer had with an electric fence the more responsive she was to the audio cue during associative training. Compared to their younger counterparts, the older heifers in this experiment would also have had greater exposure to the unpredictable environmental changes common in pasture-based dairy systems (e.g., variable environmental conditions, movement to new areas of the farm, variability in the quantity, quality and composition of feed, interactions with humans).…”