title: Calcium deficiency and food deprivation improve the response of chickens to acute heat stress.
abstract: The tolerance of chickens to acute heat stress may be modified by diet. Broiler chickens fed calcium-adequate (0.90% Ca) or -deficient (0.45% or 0.15% Ca) diets were either fed or not fed for 24 h and exposed to increasing temperatures (from 24 to 41 degrees C). Diets were fed for 7 d before heat stress in Experiment 1 and for 14 d before heat stress in Experiment 2. Body temperature, blood ionized Ca, pH, pCO2, plasma inorganic phosphate and total Ca were determined. During heat stress, Ca+2 and inorganic phosphate were depressed in all treatments. Feeding the 0.45% Ca diet for 7 d reduced hyperthermic body temperature of fed chickens but had no effect on body temperature of unfed chickens relative to the groups fed 0.90% Ca. No further improvement in body temperature response to heat stress was obtained by lowering the dietary Ca level to 0.15% or extending the feeding period to 14 d. Food deprivation was more effective in counteracting the heat-induced rise in body temperature than a dietary Ca deficiency. Heat-induced changes in body temperature, Ca+2, inorganic phosphate and blood pH were highly correlated (P < 0.001). The change in Ca+2 followed a pattern similar to that of changes in body temperature, but changes in inorganic phosphate seemed to be more indicative of changes in pH. Control birds fed 0.90% Ca exhibited the highest changes in Ca+2 and body temperature values. Feeding Ca-deficient diets reduced changes in both Ca+2 and body temperature. Unfed birds, regardless of dietary Ca level, showed the lowest changes in Ca+2 and body temperature.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Poultry Science, North Carolina State University, Raleigh 27695-7608.
authors.forename: A
authors.initials: A
authors.lastname: Ait-Boulahsen
authors.forename: J D
authors.initials: JD
authors.lastname: Garlich
authors.forename: F W
authors.initials: FW
authors.lastname: Edens
mesh_terms: D000136:Acid-Base Equilibrium; D000818:Animals; D001831:Body Temperature; D002118:Calcium / Q000097:blood / Q000172:deficiency*; D002645:Chickens; D005508:Food Deprivation / Q000502:physiology*; D006358:Hot Temperature / Q000009:adverse effects*; D008297:Male; D010710:Phosphates / Q000097:blood; D013312:Stress, Physiological / Q000503:physiopathology*
chemical_list: D010710:Phosphates; D002118:Calcium