Plant herbs or their extracted oils containing terpenoids may improve poultry health and quality of production. The effects of licorice extract in vitro and laboratory animals are reported but the influence on poultry performance has not been documented (Lee et al., 2004). This experiment was conducted to determine the effects of dietary supplementation of licorice extract derived from wild growing herb in Iran on fat digestibility, blood metabolites and broiler chicken performance. A total of 600 d-old male chicks (ross-308) were divided into fifty groups of twelve birds each and used in a completely randomized design experiment. Three phase feeding programs of starter (1-14d), grower (15-35d) and finisher (36-49d) were used to feed the birds. Two main diets in each phase were provided to have 100 and 95% of recommended digestible amino acids (RDAA). Each starter and grower diet was further divided into five sub-diets and supplemented with 0.0, 0.0(control); 2.0, 1.0 g/kg fermacto; 2.0, 1.0 (high); 1.0, 0.5 (medium) and 0.5, 0.25 (low) g/kg diet licorice extract, respectively. The two main finisher diets were fed to respected birds without any supplementation. Bird had free access to feed and water throughout the experiment. Serum cholesterol, triglyceride, glucose, VLDL, LDL and HDL concentration in d 21 were measured enzymatically in an auto-analyzer (Selectra E, Holland). One hundred leukocytes (WBC) were counted on one slide for each bird to calculate the portions of heterophil and monocyte in blood plasma and heterophil to lymphocyte Ratio. Chromic oxide containing diets (0.3%) were fed to determined the gastro intestinal transit time (GTT) of feed and fat digestibility during 16- 19 d of age. Diet and excreta chromium was determined using dry ash procedure of Miller-Ihli and Greene (1992). There was not a significant difference in body weight, feed intake and feed conversion ratio (FCR) of birds fed different feeding programs. Birds had licorice extract in their diet showed low abdominal fat content, whereas fat digestibility did not change as compared to birds fed control or fermacto contained diets. Birds fed the starter and grower diets with the high level of licorice significantly (p< 0.05) decreased their blood cholesterol (138.6 vs. 206.6) and numerically decreased (p=0.06) their LDL concentration as compared to control birds. Other biochemical blood parameters were not significantly influenced by dietary supplementation. The broiler chickens immune system (WBC) was not influenced by the addition of fermacto or licorice extract in birds diet. Birds fed diet with 100% as compared to 95% of RDAA had significantly (p< 0.05) lower FCR in the starting (1.54 vs. 1.66), growing (1.89 vs. 1.96) and/or total (1.89 vs. 1.98) periods of experiment. The GTT of feed contained fermacto and/or licorice extract was similar to control fed birds.

Keywords