The aim of the present trial was to assess the potential of orange peel extract (OPE) and lemon peel extract (LPE) as possible promoters of broilers resistance to heat stress. 2×3 factorial arrangement two levels of OPE (0 and 200 mg/kg) three levels of LPE (0, 200 and 400 mg/kg) at 28-38 d of age with 288 Ross 308 broilers Four replicates with 12 chicks for each treatment. From day 28, the basal ambient temperature was set at 26°C and this was increased daily to 34 °C with 50% relative humidity for 5 hours to induce heat stress. At the end of the trial (day 38) four birds per pen were sampled for analyses of blood parameters and intestinal tissues.Performance Dietary OPE, LPE and their interaction did not show any significant effect on body weight gain, feed intake and feed conversion ratio. Mortality was not affected by the test diets under heat stress. Blood components The inclusion of 200 mg/kg OPE significantly increased total protein, but reduced the activity of LDH and CPK in broiler’s serum. LPE significantly decreased LDH and CPK activity. The interaction of OPE and LPE at the level of 200 mg/kg OPE and 200 mg/kg LPE significantly decreased the activity of LDH. However, the effects of OPE, LPE and their interaction on other blood characteristics such as glucose were not pronounced. Gut histology Thickness of muscle layers of duodenal tissue was significantly reduced by feeding 400 mg/kg LPE; but no effect on other intestinal traits .The extracts used in the present study did not improve broiler performance during heat stress.

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