Submitted to: Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/20/2003
Publication Date: 9/13/2003
Citation: BROWN BRANDL, T.M., NIENABER, J.A., HAHN, G.L., EIGENBERG, R.A., PARKHURST, A.M. DYNAMIC RESPONSES OF FEEDER CATTLE TO SIMULATED HEAT WAVES. SYMPOSIUM PROCEEDINGS.EAAP Pub. #109, p. 335-338. 2003. Interpretive Summary: High temperature and humidity of feedlot cattle reduce performance. In the most severe cases, death can follow. A study was designed to evaluate feed intake, breathing rate, body temperature, and heat production of feedlot cattle under hot conditions. Nine steers were exposed to three different hot environments of varying patterns. It was found that breathing rate and feed intake give an accurate assessment of the animal's well being as it relates to heat.
Technical Abstract: Heat stress reduces performance and, in the most severe cases, death of feedlot cattle, resulting in major economic losses. A study was designed to evaluate the dynamics of thermoregulation and feed intake of feeder cattle when exposed to either simulated heat waves or a standard cyclic environment. Nine crossbred steers were randomly assigned to individual pens in one of three environmental chambers. Three temperature regimes (heat wave simulation from Rockport, MO 1995; heat wave simulation from Columbia, MO 1999; and Cyclic heat stress treatment of 32 +/- 7C) were administered to each of three chambers for a period of 18 days according to a Latin square treatment design, with a 10-day thermoneutral period separating treatment periods (18 +/- 7C). Respiration rate, core body temperature, heat production, and feed intake were measured on each animal for the duration of the experiment. From this study, it appears that respiration rate and feed intake, observable parameters, give an accurate insight into the thermoregulatory status of the animal during heat challenges.