Predicting beef cattle stocking rates and live weight gains on Eastern Oregon rangelands: Description of a model

Abstract

A simple deterministic model was developed to predict animal unit months (AUM's) and live weight gains of beef cattle grazing specific range types in eastern Oregon. The model can provide values for 3 levels of spatial resolution (pasture, mapping unit, and slope/ proximity to water "cells" within map ping units) and 5 monthly periods from May 15 to October 14. Operation of the model begins by calculating forage availability as a factor of forage biomass, usable acres, and desired forage utiliza tion. Grazing capacity (AUM's) is calculated by comparing forage availabil ity with the dry matter forage requirement of a 1,000 lb animal unit for 30 days. Live weight gains are calculated by comparing forage availability to dry matter forage intake, crude protein intake, and digestible energy intake of yearling heifers. The model can be used in planning range improvements and coordinating livestock management with other rangeland activities.