Search

The forage-animal interface is a vital component of agricultural systems that is often overlooked by both agronomy and animal science programs. As such, current grazing models do not always provide a satisfactory understanding of how forage species and/or cultivars respond to livestock interaction in both production and physiology, how forage can influence the animal, and how the nexus of these two entities may affect the environment. The objective of this effort was to develop a conceptual framework of a dynamic model that combined the forage and ruminant livestock interactions, and to provide the initial parameterization of a model for bermudagrass pastures. The systems dynamic methodology was used. The causal loop diagram (CLD) was first envisioned based on the hypothesis that not only can forage factors affect performance and behavior of the grazing animal, but the grazing animal, through its herbivorous behavior and selective intake, can affect and alter the physiology, growth, and performance of the forage and the pasture. Generation of a preliminary stock-and-flow diagram (SFD) with variable flight simulators was also performed. The main CLD was a composite of four sub-models that represented the agronomic, animal, atmospheric, and soil subsystems. The limitations of this model existed in the lack of meta-analytical publications in which necessary equations have been summarized that could be used in model programming. The parameterization of the model suggested that forage allowance was the driving factor in animal ADG, and forage growth rate was governed by a combination of evapotranspiration, defoliation, soil N, and precipitation. Our simulation of the bermudagrass scenario suggested that under these production conditions, most portions of the model operated in a traditional goal-seeking fashion. The initial results provided the documentation of the interface concept for the benefit of forage agronomy and animal nutrition programs as well as the foundation for advancements of the model to eventually serve as potential decision aid in production-economic strategies. [ABSTRACT FROM AUTHOR]

The forage-animal interface is a vital component of agricultural systems that is often overlooked by both agronomy and animal science programs. As such, current grazing models do not always provide a satisfactory understanding of how forage species and/or cultivars respond to livestock interaction in both production and physiology, how forage can influence the animal, and how the nexus of these two entities may affect the environment. The objective of this effort was to develop a conceptual framework of a dynamic model that combined the forage and ruminant livestock interactions, and to provide the initial parameterization of a model for bermudagrass pastures. The systems dynamic methodology was used. The causal loop diagram (CLD) was first envisioned based on the hypothesis that not only can forage factors affect performance and behavior of the grazing animal, but the grazing animal, through its herbivorous behavior and selective intake, can affect and alter the physiology, growth, and performance of the forage and the pasture. Generation of a preliminary stock-and-flow diagram (SFD) with variable flight simulators was also performed. The main CLD was a composite of four sub-models that represented the agronomic, animal, atmospheric, and soil subsystems. The limitations of this model existed in the lack of meta-analytical publications in which necessary equations have been summarized that could be used in model programming. The parameterization of the model suggested that forage allowance was the driving factor in animal ADG, and forage growth rate was governed by a combination of evapotranspiration, defoliation, soil N, and precipitation. Our simulation of the bermudagrass scenario suggested that under these production conditions, most portions of the model operated in a traditional goal-seeking fashion. The initial results provided the documentation of the interface concept for the benefit of forage agronomy and animal nutrition programs as well as the foundation for advancements of the model to eventually serve as potential decision aid in production-economic strategies. [ABSTRACT FROM AUTHOR]