WIND-CHILL E F F E C T F O R C A T T L E AND SHEEP t D. R. Ames and L. W. lnsley

Effective temperature is a term used to rate the cooling or heating power of the physical environment in terms of dry bulb temperature. For livestock exposed to cold, windy environments, effective temperature must now be predicted by a wind-chill index prepared for humans and designed without regard to extemal insulation_ suck~hai r or wool. The human wind-chill relationship is quadratic in nature. When rate of heat loss through animal hides with hair or wool was measured during exposure to temperatures ranging from -23C to 2C and wind velocities from 0 to 56 km per hour a cubic relationship was found. Data presented herein suggest that the human wind-chill index is not valid for animals with natural coverings, particularly at wind velocities greater than 40 km per hour. Instead, the relationship between rate of heat loss and wind velocity for animals with hair or wool is more accurately predicted by the cubic function which may account for the destruction of the external insulation occurring during wind speeds greater than 40 km per hour.