Authors: Thomas E. Aquino, Graduate Student, Biquan Zhao, Post-doctoral Researcher, Pedro Fernandes, Graduate Student, Mary E. Drewnoski, Professor, Yijie Xiong, Associate Professor, Animal Science, Lincoln.

Summary with Implications 

This two-year study was conducted to determine if virtual fencing (VF) could be used to manage strip grazing by comparing its performance to traditional temporary electric fencing.  The second goal was to compare the effects of strip grazing to continuous grazing on animal performance and carrying capacity. In each year, growing steers were assigned to one of three grazing treatments: continuous grazing (CONT), strip grazing with poly-wire electric fence (POLY), or strip grazing using eShepherd virtual fencing collars (VF). Overall, new strips of forage were allocated every 9.5 days, and the grazing period lasted 54-59 days. Grazing treatment did not impact individual animal performance, but strip grazing increased carrying capacity by up to 24%. The VF system also kept the steers within the virtual boundaries 99.2% of the time. These results suggest VF is just as effective as poly-wire fencing for strip-grazing management and would be useful for producers who are concerned about the labor requirements of physical fencing.

Introduction

Strip grazing is a common grazing management practice where animals are allocated to a smaller portion of a paddock for a short time, then they are allocated a new area by advancing the fence without moving a back fence. Strip grazing is commonly utilized in stockpiled dormant forages and had been shown to increase carrying capacity by up to 47% when compared to continuous grazing of the same forage (2024 Nebraska Beef Report, pp.37-41). It is hypothesized that strip grazing reduces trampling loss compared to continuous grazing, therefore increasing the amount of forage that can be consumed by the cattle. While this seems beneficial, strip grazing management requires additional fencing infrastructure and labor to maintain fences and physically allocate new forage to cattle. This increased labor may deter producers from adopting strip grazing management of dormant forages. Virtual fencing (VF) technology has proven successful as a tool to manage cattle grazing across a variety of systems by creating virtual boundaries to keep cattle contained within their designated area. Currently, there are limited data exploring the use of VF to manage strip grazing and no direct comparison of VF to traditional electric fencing in terms of managing strip grazing. The goal of this research was to determine if VF can serve as a “low labor” alternative to traditional electric fencing for producers who are concerned about the labor and fencing requirements associated with strip grazing. This would allow those producers to realize the increased carrying capacity of strip grazing, without needing to build and maintain the physical barrier fences used to allocate new strips of forage. However, the economic advantage of VF relative to poly-wire will depend on operation-specific factors such as labor availability, travel time and distance to pasture, and how frequently fences must be moved.

Procedure

This trial was conducted at the University of Nebraska-Lincoln Eastern Nebraska Research, Extension, and Education Center (ENREEC) near Mead, Nebraska, during the fall and winter of 2024-2025 and 2025-2026.

Explanation of Grazing Treatments

The three grazing treatments used in both years of this study are as follows: 1) Continuous grazing (CONT): Steers were allowed to graze the entire paddock until the forage had been utilized. 2) Strip grazing with poly wire fencing (POLY): paddocks were divided into equal strips using poly wire electric fencing. Steers were allocated new forage when they utilized the forage in the previous strip based on field inspection by technicians. 3) Strip grazing with virtual fencing (VF): the same grazing management at the POLY groups; however, instead of electric fencing, steers were managed using VF.

Crop and Field Information

In both years, the same 38-ac field was planted with 35 lb/ac of a forage mix consisting primarily of sorghum-sudangrass during June. In the first year, the crop was allowed to grow for 45 days at which point it was cut for hay. The regrowth was then allowed to stockpile for the remainder of the growing season until it was killed by frost in mid-October. In year 2, the forage was planted in June and allowed to stockpile over the entire growing season until it was killed by frost in November. After the frost, the field was divided into 6 equal paddocks using electric fencing. For this experiment, there were three fencing treatments meaning that each treatment occurred in 2 paddocks each year. In year 1, each paddock was approximately 4 ac and in year 2, the paddocks were approximately 3.5 ac. The reduced size in year 2 was due to an area of the field that was excluded due to variable forage production. For the strip grazing paddocks (POLY and VF), the paddock was sub-divided into smaller strips approximately 0.5 ac each using either physical electric fencing or through the VF platform. 

Prior to grazing, mass samples were collected from within each paddock (n = 8 in year 1 and n = 7 in year 2). All forage within a 1.6 ft² area was clipped at ground level. Upon completion of the grazing period, a post grazing sample was collected from adjacent points within the field. Pre- and post- grazing samples were transferred back to the lab and dried at 140°F to remove all moisture. To evaluate utilization of the forage the post-grazing mass was subtracted from the pre-grazing mass to determine the amount of forage that disappeared. Then the pre-grazing mass was divided by the disappearance to calculate percent utilization. 

Animal Assignment and Performance Measurements 

In both years, all steers were trained to the eShepherd system (Gallagher Animal Management, Kansas City, MO) before grazing. After the training period, cattle were limit-fed at 2% body weight for 5 days. Cattle were then weighed for 2 consecutive days. This procedure was used to equalize gut fill. Each year, sixty growing steers (578 ± 2.2 lb) were stratified by body weight and assigned randomly to one of 6 groups, resulting in 10 steers per group. To accurately calculate gains, the same limit-feeding procedure was conducted at the end of the grazing period. 

Grazing Management

            Steers were turned out for grazing in November of each year. Due to the lower nutritive value of the mature forage, all steers were supplemented with 5.5 lb per steer of dried distillers grains 3 times per week (DM basis). Continuous groups had access to their entire paddocks immediately, while POLY and VF were turned out into their initial 0.5 ac strip. New forage was allocated based on visual appraisal of the remaining forage material in the paddock with a target utilization of approximately 50%. Across both years, new strips were allocated on average every 9.5 ± 1.2 day.

In both years, the CONT groups consumed all the available forage in their respective paddocks before the strip grazing groups had used all of the strips. To allow for evaluation of steer performance, all cattle were removed from the field on day 59 in year 1 and day 54 in year 2 when the CONT had used their forage and at this point all steers were limit-fed and weighed to calculate gain. 

Data Analysis

Forage and animal performance data were analyzed as a completely randomized design (CRD) using SAS, where paddock represents the experimental unit. The grazing treatment and year were included as fixed effects. Any P-values ≤ 0.05 were considered significant, while P-values between 0.05 and 0.10 were considered tendencies.

Results

All results reported in-text are pooled across both years of the experiment. 

Forage Production and Utilization

            Pre-grazing forage mass tended to be greater (P = 0.08) in the POLY treatment (13,343 lb/ac) while VF (10,732 lb/ac) and CONT (11,235 lb/ac) were not different (P = 0.48; Table 1). This measurement was collected before grazing began, the numerical difference was not a response to grazing treatment and likely reflects underlying spatial variation in forage production and sampling. At the conclusion of the grazing period, post-grazing biomass was not different (P = 0.89) with an average residual of 5,774 lb/ac. This means that across all 3 grazing treatments, the steers grazed their paddocks to a similar end point with a similar amount of residual biomass left. Overall utilization (or the percentage of forage that disappeared from the field) was not statistically different (P = 0.68; utilization 52 ± 6%). However, because POLY began with a numerically greater forage mass but ended with a residual forage mass comparable to the other treatments, calculated forage utilization was also numerically greater for POLY. Overall, these numerical differences likely represent variability of the forage measurements rather than evidence of a grazing-treatment effect. 

Animal Performance and Carrying Capacity

Grazing treatment did not have an impact (P = 0.21) on ADG, with all steers gaining an average of 1.39 lb/day (Table 2). The most notable outcome of this study was the increase in carrying capacity with strip grazing. Carrying capacity did not differ between POLY (3.46 AUM/ac) and VF (3.44 AUM/ac; P ≥ 0.13), but both strip-grazing treatments had greater carrying capacity than CONT (2.82 AUM/ac; P < 0.01; Table 2). The increased carrying capacity was realized by achieving the same number of grazing days on less total acres by the strip grazing groups. Thus, if you were to compare on the same size field, strip grazing would result in more total grazing days as compared to continuous grazing. Given that forage utilization and steer ADG were not different among treatments, the greater carrying capacity for strip grazing is presumably due to a reduction in trampling loss. 

Virtual Fence Containment Rate

Containment rate can be used to estimate how effective the VF system was at keeping cattle contained within the virtual boundary. The eShepherd system records its location every 10 minutes. Steers with GPS coordinates within the VF boundary were denoted as contained, while points outside of the boundary area were considered escaped.  

Because POLY steers were not fitted with virtual fencing collars, containment could not be directly compared between POLY and VF. However, containment rate was evaluated within the VF treatment to determine how effectively the virtual boundaries kept cattle within their assigned grazing area. Throughout both years, the minimum average containment rate reported was 97.41%, with containment rates of 100% for a large part of the grazing period (Table 3). These containment rates show that the VF system created very effective boundaries and kept cattle contained in their designated areas throughout the grazing period.

Conclusion

            Strip grazing management can be used to increase carrying capacity when compared to continuous grazing of a stockpiled annual forage over winter. In this study, when allocating new forage every 9 to 10 days, the increase in days of grazing per acre varied from 13-24%, more than continuous grazing. Furthermore, virtual fencing serves as a very effective tool to manage strip grazing when compared to traditional electric fences as measured by similar animal performance and carrying capacity. These results indicate that virtual fencing can be used as a labor-saving alternative to physical fencing for strip grazing, particularly where the time and labor required to move fence may limit the feasibility of strip-grazing management.

Acknowledgement

This project was supported by the North Central Region of Sustainable Agriculture Research and Education (SARE) grant LNC23-492: Grazing Technologies to Enhance Integrated Crop Livestock Systems in the Northern Great Plains.