An Evaluation of Fixed Versus Variable Rotational Grazing Under Weather Uncertainty Using Simulation
Publication Date
1989
Description
Three characteristics which identify a rotational grazing system and which distinguish one rotation from another are (a) the number of paddocks or cells into which the entire pasture area is divided, (b) the scheduled grazing period or amount of time the livestock will graze on a paddock before being moved, and (c) whether the rotation is fixed or variable. With a fixed rotation, the scheduled grazing period per paddock movement is strictly adhered to whereas with a variable rotation, paddock-to-paddock movement deviates from the scheduled sequence according to some specified criterion such as minimum herbage availability. The distinction between a fixed and a variable rotation is especially critical in assessing the risk associated with a grazing system. Under draughty weather conditions, a variable rotation provides the producer with the flexibility to avoid overgrazing and reduced intake by curtailing the scheduled grazing period and moving the animals to another paddock. However, the higher frequency of paddock-to-paddock movements if adverse conditions exist results in increased labor and monitoring than with fixed rotations. With a fixed rotation under adverse conditions, the scheduled movement from one paddock to another is not altered, but there is increased risk of reduced animal performance if forage is limiting. By contrast, if under good weather the threshold of minimum herbage availability is not breached, the timing of paddock-to-paddock movements is identical for both fixed and variable rotations, resulting in similar weight gains and economic returns. The purpose of this paper is to use computer simulation to evaluate the performance of fixed and variable rotational grazing as a management alternative for a stocker-steer grazing systems. The biophysical model GRAZE is used to simulate pasture growth and animal weight gain for each of 18 rotational systems. Economic returns and weight gains under a continuously grazed system are provided as a reference for comparison. The paper extends the work of Parsch and Loewer (1987) by comparing their baseline analysis of « strictly adhered to » fixed rotational grazing to a more flexible variable rotational grazing system.
Citation
Parsch, L D.; Watts, W M.; and Loewer, O J., "An Evaluation of Fixed Versus Variable Rotational Grazing Under Weather Uncertainty Using Simulation" (2025). IGC Proceedings (1989-2023). 9.
https://uknowledge.uky.edu/igc/1989/session11/9
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An Evaluation of Fixed Versus Variable Rotational Grazing Under Weather Uncertainty Using Simulation
Three characteristics which identify a rotational grazing system and which distinguish one rotation from another are (a) the number of paddocks or cells into which the entire pasture area is divided, (b) the scheduled grazing period or amount of time the livestock will graze on a paddock before being moved, and (c) whether the rotation is fixed or variable. With a fixed rotation, the scheduled grazing period per paddock movement is strictly adhered to whereas with a variable rotation, paddock-to-paddock movement deviates from the scheduled sequence according to some specified criterion such as minimum herbage availability. The distinction between a fixed and a variable rotation is especially critical in assessing the risk associated with a grazing system. Under draughty weather conditions, a variable rotation provides the producer with the flexibility to avoid overgrazing and reduced intake by curtailing the scheduled grazing period and moving the animals to another paddock. However, the higher frequency of paddock-to-paddock movements if adverse conditions exist results in increased labor and monitoring than with fixed rotations. With a fixed rotation under adverse conditions, the scheduled movement from one paddock to another is not altered, but there is increased risk of reduced animal performance if forage is limiting. By contrast, if under good weather the threshold of minimum herbage availability is not breached, the timing of paddock-to-paddock movements is identical for both fixed and variable rotations, resulting in similar weight gains and economic returns. The purpose of this paper is to use computer simulation to evaluate the performance of fixed and variable rotational grazing as a management alternative for a stocker-steer grazing systems. The biophysical model GRAZE is used to simulate pasture growth and animal weight gain for each of 18 rotational systems. Economic returns and weight gains under a continuously grazed system are provided as a reference for comparison. The paper extends the work of Parsch and Loewer (1987) by comparing their baseline analysis of « strictly adhered to » fixed rotational grazing to a more flexible variable rotational grazing system.
