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Title: DYNAMIC RESPONSES OF FEEDER CATTLE TO SIMULATED HEAT WAVES

Author
item Brown-Brandl, Tami
item Eigenberg, Roger
item HAHN, G - USDA-ARS COLLABORATOR
item Nienaber, John
item MADER, TERRY - UNIV NEBRASKA
item SPIERS, DON - UNIV MISSOURI
item PARKHURST, ANNE - UNIV NEBRASKA

Submitted to: American Society of Agri Engineers Special Meetings and Conferences Papers
Publication Type: Other
Publication Acceptance Date: 7/31/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary: A study was conducted to determine the response of cattle to three different hot environments. One of the environments was a standard research model to simulate hot conditions, and the other two environments were recreations of actual extreme weather patterns (Columbia, MO 1999 and Rockport, MO 1995). It was found that all three environments caused similar increases in body temperature. However, the conditions from Rockport, MO 1995 caused the least increase in breathing rate and least decrease in feed consumption. The results indicated that breathing rate was the best measure of animal stress tested.

Technical Abstract: Heat stress in feedlot cattle causes reduced performance, and in the most severe cases, death of the animals, thus causing the loss of millions of dollars in revenue to the cattle industry. A study was designed to evaluate the dynamics of thermoregulation and feeding activities when feeder cattle were exposed to simulated heat waves in comparison with repeated sinusoidal hot and thermoneutral environments. Nine beef steers were randomly assigned to an individual pen in one of three environmental chambers. Each chamber was subjected to each of three temperature regimes (Heatwave simulation from Rockport, MO 1995, Heatwave simulation from Columbia, MO 1999, and Controlled heat stress treatment of 32±7C) for a period of 18 days, according to a Latin square treatment design with a 10-day thermoneutral period (18±7C) separating treatment periods. Respiration rate, core body temperature, and feed intake were measured on each animal for the duration of the experiment. Differences were found in all treatments for all parameters; however it was very apparent that severity of the stress was dependent on the response variable of interest. The response of respiration rate to temperature was found to be similar in all animals and have little acclimation effect. Therefore overall recommendation is that respiration rate was found to be the overall best indicator of stress in a group of animals.