The effect of high levels of Glycyrrhiza glabra powder on performance, carcass morphology and breast muscle fatty acid profile in broilers

We investigated the effect of a medicinal plant, namely licorice ( Glycyrrhiza glabra) powder, on performance, carcass characteristics, fatty acid profile of breast muscle, intestinal microbial flora, blood constitutes immunity of broiler chickens. Using a completely randomized design, an experiment was done in which 3 treatments, replications, and 10 chicks (45 +/- 2 g) per replication (total of 120 one-day-old male broiler chicks of commercial strain Ross 308) were used. Experimental treatments included three different levels of licorice (0, 300 and 400 mg/kg feed). The results showed that although variation in feed intake (FI), weight gain (WG) and feed conversion ratio (FCR) not significant in any of the rearing periods (P >= 0.05), the highest FI, WG and the best FCR was observed in the final riod of chickens were fed with Diet containing 400mg/kg licorice. According to the data, the best European index related to this treatment. In addition, the use of two levels of licorice had no significant effect on carcass characteristics or intestinal microbial flora; however, the highest increase in body weight and the lowest number of Lactobacillus dophilus bacteria were observed at the higher level of licorice. However, these high levels did not lead to a decrease abdominal fat. According to the results obtained, different levels of licorice led to a significant reduction of harmful such as cholesterol, triglycerides, very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) (P<0.05). Furthermore, although the level of high-density lipoprotein HDL was not significant (P >= 0.05), its highest amount was seen at high levels of licorice. In addition, the lowest amount of total protein, albumin and globulin was observed at the level of 400 mg/kg of licorice. Although the amount of glucose was the lowest, its level was not significant (P >= 0.05). The use of this same level of licorice had no significant effect on the function of the humoral immune system in response to antigen injection i.e. antibody against sheep red blood cell (SRBC) or antibody titer against Newcastle virus and influenza (P >= 0.05). Nevertheless, according to the data, the highest antibody titer against Newcastle virus and SRBC antigen was associated with this treatment. These results also showed that high levels of licorice led to increase in the number of Bifidobacterium. Villi width and crypt depth decreased at the high dose of licorice, but ratio of villi length to crypt depth increased. In addition, the use of different levels of licorice could not reduce the ratio of saturated to unsaturated fatty acids compared to the control group. Therefore, based on the results of this research, it is recommended to use the level of 400 mg/kg of licorice to supplement the diet of broilers