Utilisation of thyme powder (Thyme vulgaris L.) as a growth promoter alternative to antibiotics for broiler chickens raised in a hot climate

The impact of dietary dried thyme powder (DTP) supplementation to broilers raised in a hot climate during 1-28 days of age was studied using a total of 180, 1-day-old Arbor Acres broiler chicken males divided into 5 experimental groups (36 broilers/diet, 6 replicates of 6 broilers/replicate). Broilers were fed the same basal diet consisting of maize-soybean meal but with different supplementations: control group a) basal unsupplemented diet; DTP supplemented groups b) basal diet supplemented with 10 g/kg diet DTP (DTP-10), c) basal diet supplemented with 20 g/kg diet DTP (DTP-20) and d) basal diet supplemented with 30 g/kg diet DTP (DTP-30), and the antibiotic group e) basal diet supplemented with 1 g/kg diet Zinc Bacitracin (ZnB). All the DTP groups had a better (P < 0.01) feed conversion rate than the control. The control group and the DTP-10 and the DTP-30 groups had a significantly greater European production efficiency index than the ZnB group. The relative weight of the gizzard significantly increased due to DTP supplementation compared to the control and ZnB groups. The effect was highest when 30 g/kg DTP was fed. Supplementation with 20 and 30 g/kg DTP significantly increased blood plasma total protein compared to the other groups. In the DTP-10, DTP-20 and ZnB groups haemoglobin and mean cell haemoglobin was higher (P < 0.01) than in the control group. The ZnB group showed a higher (P < 0.01) white blood cell concentration than the control and DTP-20 groups. Plasma malnodialdehyde of chickens in DTP-10 was lower (P < 0.05) than that of chickens in the other groups, while plasma total antioxidant capacity of DTP-30 was higher than that of the control group. In addition, DTP-10 group had a significantly higher antibody titre to infectious bursa disease than the control. In conclusion, supplementation with 10 g/kg DTP (11.4 mg/kg thymol and 1.05 mg/kg carvacrol) could be used as an alternative to antibiotic growth promoters to improve feed conversion rate and immune response to infectious bursa disease while decreasing malondialdehyde of broilers raised in a hot climate during 1-28 day of age.