A virtual fence (VF) system typically consists of three main components: (1) a software interface that allows users to draw VF lines and define boundary zones on a digital map, establishing designated grazing areas and exclusion zones; (2) a GPS-enabled collar fitted around an animal’s neck, equipped with technology to track movement and deliver auditory and electrical cues to guide or restrict livestock distribution; and (3) base stations and/or cellular towers that facilitate communication between the software and the collars (Antaya et al., 2024; Ehlert et al., 2024). As of December 2025, 4 VF systems are commercially available in the United States. These trademarked systems include: eShepherd by Gallagher, Halter, Nofence, and Vence by Merck Animal Health. VF components from different manufacturers are typically not compatible or interchangeable. Although there are similarities across systems, each company offers a distinct collar design (Figure 1, Table 1) (Audoin et al., 2025). This educational material provides details on the attachment mechanisms, collar assembly, required deployment tools, and recommendations for achieving proper collar fit for each vendor
Across all systems, ensuring a proper collar fit is essential. A well-fitted collar allows animals to behave normally without discomfort, minimizes risk of injury, and ensures the correct delivery of VF cues. In any case, each VF company has recommendations on collar fit that you should follow for animal welfare reasons, and for a best use of the technology. If you are putting collars on growing animals such as heifers and steers, you will need to check the collar fitting every 6 to 8 weeks.
This publication is part of the Foundations of Virtual Fencing series. Other titles in this series include: