Effects of star anise (Illicium verum Hook.f) oil on the nuclear factor E2–related factor 2 signaling pathway of chickens during subclinical Escherichia coli challenge

Abstract We characterized the mechanism underlying star anise (Illicium verum Hook.f) oil (SAO)–mediated antioxidant status during subclinical Escherichia coli (E. coli) challenge. A total of 512 male birds (White Leghorn) at 30 wk of age with similar body weight (2.14 ± 0.02 kg) were randomly divided into 2 groups with 1 group being orally challenged with E. coli (every other day from day 15 to day 27) during the experiment. Each group of birds was then randomly allocated to dietary treatment of SAO supplementation at 0, 200, 400, or 600 mg/kg of basal diet (8 replicate cages during each treatment). The treatments were arranged a 4 × 2 factorial arrangement. The experiment comprised 1 wk of adaptation and 3 wks of data collection. There was no interaction (P > 0.05) between SAO supplementation and E. coli challenge for final body weight and average daily feed intake of birds. However, E. coli challenge resulted in a significant decrease (P