Automated Farming: Virtual Fencing

History of the virtual fencing technology
Virtual fences have been under development for many years. In 1973, a patent was granted in the United States for a system aimed at domestic animals to prevent them from moving into or out of a predetermined area without the use of visible fences. To this end, a signal emitting wire was placed to surround the area, and a receiver was mounted to the animal as a collar for producing a low-powered, high voltage electric pulse as the animal approached the wire. Although being successfully tested and still being used for dogs and cats, livestock such as goats were unable to adapt to the system. Furthermore, as it still relied on the installation of fixed wires, although them being typically underground, the system didn’t allow for flexible grazing schemes aimed at in livestock production. Throughout the nineties, a variation of virtual fencing systems was developed and a first device making use of GPS technology was patented in 1999. This new approach allowed the fences to not only be invisible, but also dynamic, thus without the need to install wires. Additionally, the new collar was emitting an audio signal preceding the electric pulse when an animal approached the virtual border. This allowed the animals to learn to associate the two signals and avoid the unpleasant electric pulses in the future by responding to the audio signals and returning to the position where they came from.Figure 1 – A herd of 5 sheep and 5 goats is used for very targeted nature management through grazing
Commercialization of virtual fencing technology
The technology was thoroughly tested and optimized over the past 20 years in terms of the position accuracy, (battery) lifetime, intensity of the electric pulse in relation to the animal species and age, the ability to support associative learning between audio signals and the electric pulse and minimize the effect on behavior and welfare of the animals wearing the collars. However, it is only since 2017 that the first virtual fencing system for livestock is commercially available. In Australia and New Zealand, Agersens commercialized the system for cattle under the brand name eShepherd®. Nofence, a Norwegian company, brought two types of collars on the European market, the first one works for both sheep and goats, and recently they introduced a collar for cattle. The US company Vence sells the technology for cattle on the American continent. All these different brands use more or less the same principle in which a collar with GPS is continuously tracking the position of the animal and checks this against the virtual borders set by the farmer and downloaded on the collar. If the animal approaches the virtual border, the collar will produce an audio signal of which the intensity and tone scale increases when the animal comes closer to the border. If the animal does not respond to the audio signal, which typically lasts for about 10 seconds, it will receive an electric pulse. The pulse has about 30 to 50 times less energy compared to a traditional electric fence, but still it is enough for the animals to be considered unpleasant. The cycle of the 10 second audio signal followed by the electric shock is repeated 2 more times if the animal doesn’t respond, the animal is indicated as ‘escaped’ and the audio signals and electric pulses are switched off until the system is reset if the animal returns to the allowed zone. The farmer gets push messages when an animal receives an electric pulse or when it is ‘escaped’ and he can get live information on the position of each individual animal and the number of audio warnings. The collars have built-in solar panels to charge the batteries during the day.Figure 2- Schematic representation of the 3 repeated cycles of audio warnings (increasing in tone and intensity) followed by an electric pulse before the farmer is notified about the ‘escaped’ animalEffect on behavior and welfare
An effective learning period is essential for the welfare of the animals and the success of the virtual fencing system. As the fences are invisible and dynamic, it is important that the animals don’t associate the virtual fences with visible land markers such as trees or (old and non-operational) physical fences. Instead, they have to associate the virtual border with the audio signal, and accordingly the electric pulse if they don’t respond to the audio signal. During the learning phase, which typically takes about 1 week, the animals have to be sufficiently exposed to the virtual borders, but the chance of them crossing the borders needs to be limited. The animals are typically placed within a physical fence that is large enough to provide sufficient feed for about two weeks, not much larger or smaller. The physical fence prevents the animals from escaping as long as they didn’t learn the system, and it controls the position of the animals and prevents them from crossing the virtual fence to some extent. Accordingly, a single virtual border is introduced on one side of the field, about 10 to 20 meters within the physical fence. If the animals have had sufficient interactions with the fence (more than 20 audio signals per animal) and the number of audio signals was more than 5 times larger than the number of electric pulses, it can be concluded that the animal has started to make the association between the audio signal and the virtual border. At that time, typically 1 or 2 days after introduction of the first virtual border, the second virtual fence line of border can be introduced and so on. After introducing the fourth virtual border and once most of the audio warnings are not followed by an electric pulse, the physical fence can be removed. From then on, the farmer can start to change the virtual area, make more complex geometries and also introduce exclusion zones. If these good practices are followed, the animals can learn the system within 1 week.Figure 3 – Schematic representation of the introduction of the virtual borders during the learning phaseOpportunities for livestock production and nature management
The use of a virtual fence for grazing animals could be beneficial for the farmer as it reduces the time spent to put up and maintain fences. The high flexibility of this system allows to change the fence daily to provide fresh pasture and support optimal animal health, welfare and production. Pastures that are normally too time consuming or not advantageous to be equipped with physical fences can still be managed efficiently with this system. Moreover, it can be used to manage cultural landscapes and nature reserves with grazers as the grazing (and trampling) intensity can be optimized in function of the envisaged nature management and conservation.Figure 4 – The virtual fencing collar for cattle (by Nofence) mounted on a Black Baldy cow. The solar panels at the side of the collar are clearly visible


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