Effects of star anise (Illicium verum Hook.f.) essential oil on laying performance and antioxidant status of laying hens.

To investigate the effects of dietary supplementation of star anise oil (SAO) on performance and antioxidant status of laying hens, a total of 864 Hy-Line brown laying hens at 26 wk of age were randomly allocated to 4 treatments with 6 replicates of 36 birds. Dietary treatments were non-star anise oil supplementation and supplemented with SAO at the level of 200, 400, and 600 mg/kg diet. The birds were fed the diets for 56 d. Average egg weight, average daily feed intake (ADFI), egg mass, laying rate, and feed conversion of each replicate were measured. Blood and liver samples from 12 birds were obtained, 72 eggs were picked out, per treatment at day 28 and day 56 of the experiment, and eggs stored for 56 d, to determine antioxidant status in serum, liver, and yolk. All laying hens had similar average egg weight, egg mass, laying rate, and feed conversion in day 29 to day 56 or the entire period of the experiment but significant difference on ADFI in day 1 to day 56. However, increasing diet concentration of SAO tended to improve (P < 0.10) egg mass, average egg weight, and ADFI in day 1 to day 28. Supplementation of SAO linearly increased (P < 0.05) activities of total superoxide dismutase (T-SOD) (day 28 and day 56) and glutathione peroxidase (GSH-PX) (day 56) in serum, GSH-PX (day 28 and day 56) in liver and total antioxidant capacity (T-AOC) (day 56) in serum and liver, but linearly reduced (P < 0.05) concentrations of malondialdehyde (MDA) (day 28 and day 56) in liver. Supplementation of SAO linearly increased (P < 0.05) T-SOD activity at day 14 and day 28, reduced (P < 0.05) MDA concentration at day 42 and day 56 of the experiment in yolk. Increasing content of SAO linearly (P < 0.05) increased T-SOD activity in yolk of eggs stored at day 0, 14, 28, 42, and 56, decreased MDA content of eggs stored at day 42 and 56, whether laying hens fed diets for 28 or 56 d. Dietary supplementation of SAO enhanced laying performance and overall antioxidant status of laying hens in a dose-dependent manner.