Calcium deficiency and food deprivation improve the response of chickens to acute heat stress.
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)
Ait-Boulahsen
A
A
Department of Poultry Science, North Carolina State University, Raleigh 27695-7608.
Garlich
J D
JD
Edens
F W
FW
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*
D010710:Phosphates; D002118:Calcium