Effects of water misting and shade on heat stress in feedlot cattle.
F. M. Mitloehner*1 , J. L. Morrow-Tesch2, J. W. Dailey2 and J. J. McGlone1; 1Texas Tech University, Lubbock and 2USDA-ARS, Lubbock.

    A total of 32 Charolais cross feeder cattle were used to assess the impact of heat stress on behavior, physiology, and production during late summer 1998. The objective was to determine the effects of the provision of shade and (or) water misting to minimize heat stress. For behavior measures the model was a split split plot. Treatments were: (1) shade and misting (SHMI), (2) only shade (SHAD), (3) only misting (MIST), and (4) no shading or misting (CONT). Two heifers were housed per pen. Maximum ambient temperature during late August was 324C and humidity 628%. Behavior was continuously video recorded over 3d. Walking, standing, lying, feeding, drinking (main plot) and the location where these behaviors were performed (shaded or misted area) were measured and analyzed on a daily and hourly basis. Rectal temperatures, respiration rates as well as average daily gain were measured. Heifers in CONT spent more time lying down than the treated animals (SHMI=4.04.24, SHAD=3.53.24, MIST=3.68.24, CONT= 4.98.29, P<.01). Cattle in CONT (1.37.37) spent less time (P<.01) standing than SHAD (3.15.31) and MIST (2.68.31) cattle. Standing behavior in SHMI (2.27.31) was not different from SHAD or MIST. Misting lowered (P<.001) rectal temperature and misting and shade combined showed an additive effect of lowering respiratory rates in heifers (SHMI=30.03.3, SHAD=33.02.8, MIST=, CONT=46.73.3, P<.05). Average daily gains between the four treatments did not differ significantly. The guide for the care and use of agricultural animals in research and teaching identifies a requirement for cooling for beef cattle during heat. Our results indicate that cattle without shade or misting have a physiological stress response to heat (increased RR and rectal temperature) and alter their behavior as a result. MIST and SHAD appear to be equivalent solutions to reducing heat stress and their effects are largely additive.

Cattle, Heat Stress, Shade 


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