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Utilizing laboratory and field studies to determine physiologically adaptive responses of cattle to multiple environmental stressors
Author(s) -
Brad Scharf A,
Johnson Jay S,
Vellios Hillary L,
Weaber Robert L,
Spiers Donald E
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1053.17
Subject(s) - stressor , rumen , zoology , heat stress , biology , environmental stress , core temperature , environmental science , ecology , food science , fermentation , medicine , neuroscience
Heat stress studies are often conducted using short‐term, controlled laboratory exposures or long‐term field exposures. Each approach has limitations, and provides only a partial understanding of complex interactions between simultaneous environmental stressors. Heat stress and fescue toxicosis, resulting from intake of endophyte‐infected fescue, have significant impacts on physiological processes with multiplicative interaction. We used numerous physiological measures of thermal status to compare responses of cattle to chamber “stress tests” and “naturally occurring” field conditions. Two controlled heat challenges were conducted (Brody Environmental Center; University of Missouri) separated by a 2‐month summer field exposure when Angus steers (N=23; 318±8 kg BW) consumed either endophyte‐infected or uninfected fescue. During the heat challenge trials, steers were randomly assigned to diets of either 0 or 40μg ergovaline/kg/d to maintain the fescue toxicosis state. Telemetric temperature transmitters in the rumen of each animal monitored core temperature. Some variables (e.g., feed intake, sweat rate, and rumen temperature) showed no change between tests, while others (e.g., rectal temperature) showed adaptation. Ultimately, a new thermal strain index for multiple stressors will be developed that identifies “real world” adaptation. Agreement No. 58‐6227‐3‐016