Effect of chronic heat stress (CHS) (at 35°C) on the intestinal mRNA levels of heat shock protein 70 (Hsp70) (A), heat shock transcription factor (HSF)-1 (B) and HSF3 (C) in control and thermal manipulation (TM) broiler chickens (n = 5). The values in the chart indicates folds of mRNA level in the control group day 0. *Within same day, mean ± SD of TM is significantly different compared to control (P < 0.05). #Within the control group, mean ± standard deviation (SD) of day 1, 3, 5, or 7 is significantly different compared to day 0 (P < 0.05). $Within the TM group, mean ± SD of day 1, 3, 5, or 7 is significantly different compared to day 0 (P < 0.05).