Simulation of herbage dynamics and livestock grazing

Typescript (photocopy).In order to accurately describe animals at pasture, it is necessary to have dynamic, dimensionally precise expressions of the relationships among the variables of animals, forage, land area and time. A dynamic, animal-unit approach is developed to calculate stocking variables such as stocking density, stocking rate and grazing pressure. In this development, some expressions found in the literature are questioned and new expressions are developed. A computer simulation model (DYNAMIC) is developed to perform calculations of those stocking variables for a hypothetical herd at pasture. This model is the first generation of more sophisticated future software suitable for calculations of stocking variables using microcomputer technology. A simulation model of the herbage dynamics of a warm-season perennial grass (GRASS) is developed as a component of a future, larger, general model of the grazing process. The conceptual and computer description of the model provide a functional framework for future research into aspects of herbage dynamics and livestock grazing. Both GRASS and DYNAMIC are first generation models which with additional development should serve as useful submodels within larger models of livestock grazing