Growth performance and gut health parameters of finishing broilers supplemented with plant extracts and exposed to daily increased temperature

The effects of three plant extracts, i.e. lemon peel extract (LPE), orange peel extract (OPE) and Curcuma xanthorrhiza essential oil (CXEO), on the performance and gut health parameters of broilers exposed to high temperature was investigated. A total of 336 unsexed Ross 308 broilers were distributed to seven dietary treatments, a control diet and six diets containing 200 or 400 mg kg(-1) feed of one of the three products between d 25-38 (12 chicks per pen, four replicates). To induce chronic heat stress, the temperature was increased to 34 C with 50% relative humidity for 5 h daily starting from d 28 until d 38. At d 38, four animals per pen were sampled for morphological characteristics (duodenum, jejunum and ileum) and microbial counts (ileo-cecal contents). Plant extracts did not affect the bird performance. The bursa weight of the control birds was lower (p < 0.05) comparing to those fed 400 mg kg(-1) OPE and 200 and 400 mg kg(-1) CXEO diets. Feeding 400 mg kg(-1) of LPE decreased the duodenal villus:crypt ratio compared to control and 200 mg kg(-1) OPE fed birds. Plant extracts did not have effect on ileal histo-morphology. Feeding with 400 mg kg(-1) of LPE and CXEO caused a decrease in coliform counts in ileum and feeding of 400 mg kg(-1) CXEO diet decreased coliform counts in caecum compared to control birds (p < 0.05). These results elucidate that CXEO, OPE and LPE might modify some microbial and intestinal traits, but without beneficial effect on performance of broilers under heat stress.