Twenty-four crossbred feedlot heifers average body weight 292 kg have been selected to assess the effect of heat stress and its relief by shade and (or) water misting on physiology and behaviour. The follOwing treatments for the experiment were used: 1) no shading or misting (control); 2) only misting (MIST); 3) only shading (SHADE); and 4) shading plus misting (SH + MI). The observation were included head in the feed bunk, head in or above the waterer, walking, standing, and lying behaviour. Physiological reactions like rectal temperature and respiration rate as well as dry matter intake, average daily gain, and feed: Gains were measured. The control heifers spent more time lying down than others (P< 0.01). In addition, control heifers spent less time (P < 0.01) standing than SHADE and MIST heifers. Misting decreased (P<0.01) rectal temperature and MIST as well as SHADE lowered (P<0.05) respiration rates.
