Thermal balance of cattle grazing winter range: Model development

Abstract Beef cattle grazing semi-arid foothill range of the Northern Rockies during winter may be exposed to cold temperatures and high winds while grazing pastures with low nutritional value. We refined a simple thermal balance equation to model heat exchange of free-ranging cattle. We account for the complex interactions between animal behavior and the changing natural environment by applying the components of the model to a rotating ellipsoid representing a cow at different orientations to the sun and wind. Correlation coefficients ( r ) between predicted standard operative temperature and measured surface temperature ranged from 0.82 on an individual basis to 0.88 on a herd average basis, indicating the model successfully quantifies heat exchanges of cattle exposed to cold conditions in the field.