In livestock production, grazing is an excellent tool but is highly specific to the conditions and goal of each operation. This variability in production systems has led to a discussion on what is the best way to graze for different situations. A description of the basics of continuous grazing and rotational grazing is a starting point for this conversation.
Rotational grazing can be subdivided into a high-intensity, low-frequency grazing system (HILF), and a low-intensity, high-frequency (LIHF) grazing system. Both grazing systems have the ability to affect forage production, forage quality, and livestock production. Within rotational grazing, both have benefits. An optimal grazing system is a combination of techniques that allow for flexibility, and account for current conditions and operation experiences. This fact sheet is an overview of grazing systems and evaluates the intensity and frequency of grazing systems for producers and agricultural professionals.
Grazing Systems
For livestock producers using pasture grazing, deciding which grazing system is best for their operation is an important discussion. Grazing systems are divided into two main groups:
- continuous
- rotational
Continuous grazing systems are characterized as a single-pasture system where livestock have access to the whole pasture for the entirety of the grazing season. This system has the benefit of being a relatively low-cost and low-maintenance approach to grazing. However continuous grazing systems do have disadvantages, namely, lower forage and livestock production due to various factors:
- sub-optimal forage quality and growth
- uneven grazing and manure distribution
- forage loss through trampling and weed competition
Rotational grazing systems use more than one paddock in a pasture to restrict livestock grazing to a certain area. After an amount of time based on forage removal goals, livestock are then rotated to an ungrazed paddock, allowing the original paddock time for forage regrowth before allowing new grazing. Rotational grazing systems flip the advantages and disadvantages of a continuous grazing system. Rotational grazing systems have greater input in terms of fencing, other infrastructural additions, and additional labor due to the rotation of livestock between paddocks. It is also important to note that access to water can be an important factor in the setup cost of some rotational grazing systems. One advantage of rotational grazing is an average increase in forage production of 30% which allows for a greater stocking rate (Rouquette et al., 2023). Rotational grazing systems will, however, require producers to make decisions on what level of intensive management is needed.
Rotational grazing systems can be designed to use a spectrum of grazing intensity and rotational frequency levels. The intensity of a rotational grazing system is determined by the relationship between the amount of forage removed in a single grazing session, the amount of time livestock are in a single paddock, and the amount of time needed for the forage to regrow the amount removed. This percentage of forage removed per grazing period in conjunction with the necessary rest period for the forage’s regrowth are core elements of a rotational grazing system. Once established, they can be adjusted by aspects such as total available pasture, paddock size and number, stocking rate, and seasonal forage regrowth. Figure 1 demonstrates the difference between three grazing systems. Solid lines represent the paddock divisions that may be permanent or temporary fencing. The livestock graze in a clockwise circular fashion.
Low-Intensity, High-Frequency
A low-intensity, high-frequency (LIHF) rotational grazing system has a low forage removal percentage per grazing period coupled with a short rest period. An example of an LIHF rotational grazing system consists of introducing livestock to a paddock with a forage height of 9 inches, allowing them to graze it down to a height of 6 inches (a rough removal of 33%), and then resting that paddock 12 days before grazing again. In this system, livestock are often moved twice as frequently as its low-frequency counterpart. Due to the additional investment in fencing, the LIHF system has a higher investment cost. But the additional cost of rotational grazing—specifically high-frequency grazing—can be reduced by using temporary fencing such as electric polynets or polywire. These types of temporary fencing allow for adjustments to paddock sizes as the season progresses while also eliminating the need for multiple permanent fences. The drawback of temporary fences is the additional labor required to move the fences, the additional need to electrify the fence, and the likelihood of higher rates of livestock escape.
High-Intensity, Low-Frequency
A high-intensity, low-frequency (HILF) grazing system has a high-forage-removal percentage per grazing period coupled with a long rest period. An example of an HILF rotational grazing system is introducing livestock to a paddock with a forage height of 12 inches, allowing them to graze it down to a height of 4 inches (a rough removal of 66%), and then giving that paddock 30 days rest before grazing again (Fig. 2).
If the paddock size and the number of grazing livestock were the same between an LIHF and an HILF grazing system, the LIHF rotational grazing system would require a greater frequency of rotation. An example of a possible LIHF and HILF rotation grazing system would be a rotation that allows 15 days of forage regrowth and 30 days of forage regrowth, respectively. The number of paddocks needed is dependent on the stocking rate. If the livestock consume the 3 inches of forage shown in Figure 2 for the LIHF example, then 16 paddocks of that size and forage mass are needed to allow for the 15 days of forage regrowth. To lower the labor of moving livestock daily, the size of the paddock can be increased to allow livestock to be moved every three days. This rotation would consist of six paddocks of the increased size to allow for forage regrowth.
What is the Effect on Forage Production?
When compared to a continuous grazing system, a rotational grazing system increases the forage biomass produced per acre of pasture. This increase is mainly a result of how the growth rate of forages varies based on the amount of the forage’s biomass (Barker et al., 2010). When forages are small, their growth rate is limited by the amount of leaf area available for photosynthesis. As forages grow, their growth rate increases until they reach their optimal growth rate. From that peak, the forage growth rate begins to decline as the forage self-shades and transitions into producing seeds instead of vegetative matter. Figure 4 shows how an HILF grazing system and an LIHF grazing system attempt to optimize forage production by optimizing the forage regrowth rate. LIHF attempts to stay at the top of the regrowth rate curve allowing roughly 4500 pounds per acre to be present. Grazing reduces the available forage to 3500 pounds per acre when the livestock are removed from the pasture. While HILF would have roughly 5000 pounds per acre available, grazing reduces regrowth to 3000 pounds per acre, resulting in the forage having a slower average regrowth rate before being grazed on during the next rotation.
When put into practice, whether an LIHF or an HILF rotational grazing system leads to an increase in forage production has shown mixed results. Some studies show no significant increase in forage production when comparing the two rotational grazing systems, while others find that the LIHF rotational grazing system increased forage production.
Species Affect
A key component in comparing LIHF and HILF rotational grazing systems seems to be the forage species present in the paddock. A study by Volesky and Anderson (2007) comparing LIHF and HILF grazing systems with similar forage heights found no difference in forage production for orchard grass (Dactylis glomerata) and meadow bromegrass (Bromus reparius), However, the same study found that the LIHF treatment resulted in greater forage production in smooth bromegrass (Bromus inermis).
A variance in forage production results based on the type of rotational grazing intensity was further observed at The Ohio State University research stations in 2021 and 2022. Verhoff (2023) observed an increase in forage production in tall fescue (Schedonorus arundinaceus) pastures under the LIHF rotational grazing treatment compared to the HILF treatment. When the study was repeated in an orchard grass pasture, no difference in forage production was found.
What is the Effect on Forage Quality?
The amount of forage produced is only one side of the coin—we also want livestock to graze on high-quality forage. Forage quality can change when using a rotational grazing system rather than a continuous grazing system. Rotational grazing limits selective grazing by livestock, which reduces grazing on mature forage with low digestibility due to the forage’s reproductive growth.
When comparing the effect of the intensity of rotational grazing systems on forage quality, one key component is the leaf-to-stem ratio consumed by grazing livestock. The stem of forages has a higher lignin content and is less palatable than the leaf portion of forages, so a higher consumption of leaves as compared to stems would result in consumption of an overall higher-quality forage. An LIHF rotational grazing system is expected to have an increased leaf-to-stem ratio compared to the HILF treatment because LIHF grazing removes a lower percentage of forages during each grazing session. This reduction in grazing sessions provides more leaf material for grazing and does not force livestock to graze on the stems before being moved to a fresh paddock. The scientific literature is, however, inconsistent, similar to the results of forage production based on forage species. Verhoff (2023) observed no difference in forage quality as a result of grazing intensity in a tall fescue pasture. In a comparison of predominantly orchard grass pastures, LIHF rotational grazing provided higher forage quality with significantly higher crude protein and lower acid detergent fiber (ADF) metrics than the HILF-managed pasture. Volesky and Anderson (2007) also found higher-quality forages in the LIHF grazing system, but only during the latter half of the growing season for orchard grass and bromegrass species.
Another aspect that may play a role in forage quality is the pasture species composition—the ratio of legumes to grass. Species composition and legume persistence are greater in an HILF grazing system due to the higher forage removal percentage per grazing session. The greater removal percentage limits the selective grazing of legumes and diminishes the grass canopy, allowing for a more advantageous environment for legumes to compete and regrow.
What is the Effect on Livestock Production?
Optimizing the forage production and quality of a pasture is a great foundation for a grazing system, but if effects are not seen in livestock production the benefits of an LIHF rotational grazing system may be limited. When comparing LIHF and HILF grazing systems, the impact on livestock production is contested. Schons et al. (2021) found that sheep grazing on an Italian ryegrass (Lolium multiflorum) pasture in an LIHF rotational grazing system had 1.4 times greater liveweight gain per acre than sheep grazing in a pasture using an HILF rotational grazing system. That increase in livestock production seen by Schons et al. (2021) is contrary to the findings of Verhoff (2023), where no positive or negative effect was observed in sheep grazing in tall fescue or orchard grass pastures. Similar results were seen in beef cattle. Portugal et al. (2022) observed an increase in the average daily gain of individual cattle in an LIHF rotational grazing system on sorghum pasture. However, due to the ability to stock more cattle on the HILF-treated pasture, the total livestock production of both systems showed no difference. Overall, present research points to the conclusion that the effectiveness of either rotational system over the other is variable based on the forage species present.
Creating A Flexible Grazing System
The production of a grazing system is dependent on many variables such as forage species, climate, and a producer's desired outcome. When compiling scientific literature assessing the efficacy of grazing systems, the number of species and different mixes of forages that can be present in a pasture makes it hard to determine definitive best practices. Pastures can include any number of grasses, broadleaves, warms-season plants, or cool-season plants, which all respond differently to management practices. Creating a flexible grazing system allows you to adjust your practices for your pasture.
Temporary fencing, an adjustable electrical source, and portable water add flexibility to your grazing system. They allow a rotational grazing system to be adjusted by stocking rate and forage allowance. For instance, during summer drought conditions, a flexible rotational grazing system allows the size of the paddock to be increased based on available forage. Using an LIHF grazing strategy in the fall prevents overgrazing as growth rates slow and the growing season ends. Grazing system flexibility also allows for adjustments because of severe weather. Figure 5 shows the importance of the need for a sacrificial or holding area to limit the effects of trampling and compaction during a heavy rainfall event.
Conclusion
Rotational grazing systems optimize the production of forages and livestock. They increase stocking rates by an average of 30% over continuous grazing systems (Rouquette et al., 2023). Rotational grazing practices also provide flexibility in the level and use of intensive management. While differences are observed in forage production and quality, the lack of consensus on impacts to livestock production, particularly in pastures of the midwestern United States, makes it premature to recommend LIHF rotational grazing as a management strategy for season-long grazing. Combining both LIHF and HILF grazing strategies may allow for the use of LIHF during the spring flush to manage and promote high-quality forage production in cool-season pastures, and in the fall to extend grazing periods. An HILF rotational grazing strategy may then be used during the summer months to allow for better forage recovery when forage regrowth rates are slowed due to heat and drought.
Additional Resources
References
Barker, D.J., Ferraro, F.P., Nave, R.L.G., Sulc, R.M., Lopes, F., & Albrecht, K.A. (2010). Analysis of herbage mass and herbage accumulation rate using gompertz equations. Agron. J. 102(3), 849–857.
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Portugal, T.B., Szymczak, L.S., de Moraes, A., Fonseca, L., Mezzalira, J.C., Savian, J.V., Zubieta, A.S., Bremm, C., de Faccio Carvalho, P.C. & Monteiro, A.L.G. (2022). Low-intensity, high-frequency grazing strategy increases herbage production and beef cattle performance on sorghum pastures. Animals, 12(1), 13.
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Rouquette, F. M., Jr, Sollenberger, L. E., & Vendramini, J. M. B. (2023). Grazing management and stocking strategy decisions for pasture-based beef systems: Experimental confirmation vs. testimonials and perceptions. Translational animal science, 7(1).
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Verhoff, K. (2023). Forage and livestock response to varied rotational stocking systems [Master’s thesis, The Ohio State University].
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Volesky, J.D. & Anderson, B.E. (2007) Defoliation Effects on Production and Nutritive Value of Four Irrigated Cool-Season perennial Grasses. Agronomy Journal, 99(2), 494–500.
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