Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/1999
Publication Date: N/A
Technical Abstract: Charolais cross feeder cattle (n=32) 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. Treatments were (1) shade and misting (SHMI), (2) only shade (SHAD), (3) only misting (MIST), and (4) no shading or misting (CONT). Maximum ambient temperature during late August was 32 plus or minus 4 degrees C and humidity 62 plus or minus 8%. Walking, standing, lying, feeding, drinking 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 plus or minus.24, SHAG=3.53 plus or minus.24, MIST=3.68 plus or minus.24, CONT=4.98 plus or minus.29, P<.01). Cattle in CONT (1.37 plus or minus.37) spent less time (P<.01) standing than SHAD (3.15 plus or minus.31) and MIST (2.68 plus or minus.31) cattle. Misting lowered (P<.001) rectal temperature and misting and shade combined showed an additive effect of lowering respiratory rates in heifers (SHMI=30.0 plus or minus3.3, SHAD=33.0 plus or minus2.8, MIST=37.3 plus or minus3.2, CONT=46.7 plus or minus3.3, P<.05). Average daily gains between the four treatments did not differ significantly. 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.