Effect of Illicium verum or Eucommia ulmoides leaf extracts on the anti‐stress ability, and mRNA and protein expression of Nrf2 and TNF‐α in Duroc × Landrace × Yorkshire and Chinese native Licha‐black nursery piglets

Abstract Plant extracts are considered to be an effective alternative to antibiotics in response to weaning stress in piglets. This study evaluated the effect of Illicium verum extracts (IVE) or Eucommia ulmoides leaf extracts (ELE) on growth performance, serum and liver antioxidant ability of nursery piglets, as well as the difference of IVE and ELE on Duroc × Landrace × Yorkshire (DLY) and Chinese native Licha‐black (LCB) piglets. A total of 96 nursery piglets (48 DLY and 48 LCB piglets) with an average body weight of 11.22 ± 0.32 kg were randomly divided into four treatments in a 2 × 4 factorial design. Each treatment had four replicates with 3 DLY and 3 LCB piglets per replicate respectively. Treatments included: basal diet, basal diet + 500 mg/kg IVE, basal diet + 250 mg/kg ELE and basal diet + 50 mg/kg chlortetracycline (CHL). All piglets were housed individually for the 42 days trial period after 7 days adaptation. Results showed that there were significant interactions ( p < .05) between piglets species and dietary treatments in average daily gain (ADG) and feed efficiency, serum and hepatic glutathione peroxidase (GSH‐Px) and malondialdehyde (MDA), hepatic integral optical density (IOD) of α‐tumour necrosis factor ( TNF‐α ), hepatic relative mRNA expressions of nuclear factor erythroid 2‐related factor 2 ( Nrf2 )/ TNF‐α and protein expression of TNF‐α . Regardless of piglets species, supplementation with IVE and ELE increased ( p < .05) ADG and feed efficiency, T‐SOD and GSH‐Px in serum and liver, hepatic IOD of Nrf2 , hepatic mRNA and protein expression of Nrf2 / TNF‐α . However, CHL treatment resulted in lower ( p < .05) serum GSH‐Px and hepatic mRNA and protein expression of Nrf2 / TNF‐α , and higher hepatic MDA and IOD of TNF‐α . Compared to LCB, DLY piglets had higher ( p < .05) ADG and feed efficiency, serum and hepatic MDA, and protein expression of TNF‐α , but lower ( p < .05) ADFI, liver index, serum and hepatic GSH‐Px, hepatic IOD of TNF‐α , mRNA expressions of Nrf2 / TNF‐α were observed. In conclusion, Illicium verum (500 mg/kg) and Eucommia ulmoides leaf (250 mg/kg) extracts can increase the growth performance and antioxidant ability of DLY and LCB piglets, while chlortetracycline produces undesirable side‐effects on the antioxidant ability of DLY and LCB piglets. Illicium verum and Eucommia ulmoides leaf extracts produced different antioxidant effects in DLY and LCB piglets with the Chinese native Licha‐black pig responding better than Duroc × Landrace × Yorkshire.