Use of lemongrass essential oil as a feed additive in quail's nutrition: its effect on growth, carcass, blood biochemistry, antioxidant and immunological indices, digestive enzymes and intestinal microbiota

The present study was designed to assess the impact of dietary supplementation of lemongrass essential oil (LGEO) on growth performance, carcass traits, liver and kidney function, immunity, antioxidant indices and caecal microbiota of growing quail. A total of 200 Japanese quails at 1-week-old were haphazardly allotted to 5 groups of 40 chicks in five replicates (8 per replicate). The first group was the control group, while LGEO was added at levels of 150, 300, 450, and 600 mg/kg diet in the 2nd, 3rd, 4th and 5th groups, respectively. Dietary supplementation of LGEO (150, 300 and 450 mg/ kg diet) increased body weight at 3 and 5 wk of age, and increased body weight gain during all periods compared with the control group (P < 0.05). All levels of LGEO improved feed conversion ratio during the periods from 1 to 3 and 1 to 5 wk of age. During 3 to 5 wk, feed conversion ratio was improved in quails fed LGEO (300 and 450 mg/kg diet) compared with the control and other treatments. Carcass traits, plasma globulin, alanine aminotransferase, and urea values did not differ among the treatments (P > 0.05), but the activity of aspartate aminotransferase in the plasma was significantly decreased (P < 0.05) in LGEO-treated groups. The total protein and albumin values were significantly increased (P < 0.05) in quails fed levels of LGEO (except 600 mg/kg diet) compared with the control. The inclusion of LGEO in quail diets improved (P < 0.05) plasma lipid profile. The dietary supplementation of LGEO increased (linear and quadratic, P < 0.05) plasma immunoglobulins (IgM, IgG, and IgA) levels, lysozyme values and activities of superoxide dismutase, total antioxidant capacity, reduced glutathione and catalase compared with the control group. The caecal Coliform, E. coli and Salmonella were lowered (P < 0.0001) in the quails treated with all LGEO levels, but the total bacterial count and Lactobacillus count were increased with dietary supplementation of LGEO levels (300 and 450 mg/kg) compared with those in the control group. The activities of digestive enzymes were significantly higher in birds fed the diet supplemented with LGEO levels than those fed the control diet. In conclusion, dietary supplementation of LGEO can improve the performance, lipid profile, immunity and antioxidant indices and decline intestinal pathogens and thus boost the health status of growing quail.