Shade and water misting effects on behavior, physiology, performance, and carcass traits of heat-stressed feedlot cattle

One hundred twelve crossbred feedlot heifers were used in two experiments t o assess the impact of heat stress and its relief by shade and(or) water mi sting on behavior, physiology, performance, and carcass traits. Treatments were 1) no shading or misting (CONT); 2) only misting (MIST); 3) only shadi ng (SHADE); and 4) shading plus misting (SHMI). Head in the feed bunk, head in or above the waterer, walking, standing, and lying behaviors were obser ved. Rectal temperature, respiration rate, and carcass traits were measured , as well as DMI, ADG, and feed:gain. Dietary NEm and NEg concentrations we re calculated from performance data. In Exp. 1, (32 heifers; average BW 288 kg) the CONT heifers spent more time lying down than all others (P < 0.01) . In addition, CONT heifers spent less time (P < 0.01) standing than SHADE and MIST heifers. Misting decreased (P < 0.0 1) rectal temperature and MIST as well as SHADE lowered (P < 0.05) respiration rates. In Exp. 2 (80 heife rs; average BW = 336 kg), lying and walking behaviors did not differ among treatments, but shade increased (P < 0.01) standing behavior in heifers. Th e MIST cattle performed less (P < 0.05) head-above-waterer behavior than un misted cattle. Rectal temperatures did not differ among treatments, but res piration rate was lower in shaded than in unshaded heifers (P < 0.05). Shad ed compared with unshaded heifers had greater DMI (9.46 vs 8.80 +/- 0.14 kg /d, P < 0.01) and ADG (1.6 vs 1.41 +/- 0.1 kg/d, P < 0.01). Heifers provide d with shade reached their target BW 20 d earlier than the unshaded heifers and differed in final BW (547 vs 520 +/-6 kg, P < 0.01). Feed:gain and cal culated NEg and NEm concentrations did not differ among treatments, and car cass traits were generally similar among treatments. In conclusion, cattle without shade had a physiological and behavioral stress response to heat th at negatively affected productivity. Providing shade for beef cattle was a suitable solution to decrease heat stress and to lower the negative effects of heat on performance, whereas misting was largely ineffective.