It is known that ascorbic acid (AA) supplementation can ameliorate the chicken’s responses to heat stress. The
influence of AA on heart heat shock protein 70 (hsp70) and plasma corticosterone (CS) was evaluated in young male
broiler chickens fed either no AA (N-AA) or 500 mg AA ykg (AA) and exposed to cyclic high temperatures (21 to 30
to 21 8C) over a 3.5 h period on three consecutive days. Dietary AA supplementation elevated plasma AA and
maintained it at high levels after heating, but in N-AA birds, only heat elevated plasma AA. In N-AA fed chickens,
plasma CS was elevated and was further increased by heat stress as compared with AA-fed birds. Heart hsp70 expression
was greater in N-AA-fed chickens compared to AA-fed chickens, and heat stress further elevated hsp70 in both N-AAand
AA-fed birds. The hsp70 increase after heat was two-fold greater in N-AA- vs. AA-fed birds. Plasma CS and heart
hsp70 were positively correlated, plasma AA and heart hsp70 were negatively correlated, and plasma CS and AA were
negatively correlated. It was concluded that chickens experience a less severe stress response after exposure to high
temperatures when they are provided dietary AA.
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