Med. Weter. 75 (4), 247-252, 2019

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Effect of dietary supplementation with extracts of rosemary, olive leaves, pine bark and quercetin on selected performance indices of broiler chickens and microbiological status of their ileum
A total of 180 1-day-old male Hubbard Flex broiler chickens were used in a 32-day model experiment to determine the effects of dietary supplementation with quercetin (Q) and with polyphenolic extracts of rosemary (RO), olive leaves (OL) and pine bark (PB) on the performance of the birds and the microbiological status of their ileum. The chickens were randomly allocated into 9 groups: the control group (with 6 replicates, 6 birds per cage) and 8 treatment groups (with 3 replicates in each, 6 birds per cage), and fed ad libitum throughout the experimental period with a basal isoenergetic and isoprotein control diet or with the same basal diet containing two concentrations of RO, OL and PB extracts (2.50 and 5.00 g/kg), and Q (0.25 and 0.50 g/kg). The body weight gain (BWG) and the feed conversion ratio (FCR) were determined during the experiment. At day 32, two randomly selected birds from each cage were slaughtered, and 5-centimetre-long pieces of the ileum beginning from the Meckel's diverticulum were collected to analyze the number of microorganisms in the intestinal content. Chickens’ weight gain and FCR were not affected by the OL-, PB- and Q-enriched diets, but supplementation with RO significantly (P < 0.05) impaired FCR. BWG was significantly (P < 0.05) reduced when chickens were fed with mixtures containing 2.50 and 0.25 g/kg of the polyphenolic additives. The number of CFUs of intestinal microorganisms was not significantly affected (P > 0.05) by the diet modification. However, a large decrease (P > 0.05) was observed in the CFUs of coliform bacteria (up to 96%), E. coli (up to 93%), Lactobacillus spp. (up to 89%), molds and yeasts (up to 95%) and anaerobic Clostridium spp. (up to 52%) in the ileum content of chickens supplemented with the additives containing polyphenols.
Key words: polyphenolic extracts, quercetin, DPPH, broiler chickens, performance, microbiological status of ileum