Supplementing exogenous xylanase improves the liver antioxidant capacity and immune response of Tibetan sheep fed wheat-based diets

Xylanase is a heteropolysaccharide found in the plant cell wall, which aids in the absorption and utilisation of nutrients. When embedded in animal feed, it enhances nutrient availability, leading to improved animal performance. The aim of this study was to explore the effect of xylanase supplementation in wheat-based feeds on the hepatic development, antioxidant capacity, and immune response in Tibetan sheep. Sixty healthy, weaned, non-neutered male lambs (19.35 ± 2.18 kg) were randomly assigned to two equal groups (n = 30 per group). Dietary treatments were: basal diet (H group), and basal diet with 0.2% xylanase supplementation (E group). After a 10–day adaptation period, the feeding trial was carried out for 90 days. The live weight, morphology, antioxidant capacity and immune response were measured. The differential genes in liver were identified by RNA-sequencing. Our results showed that the levels of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) were significantly higher in E group than in H group (p < 0.05). Enzyme-linked immunosorbent assay (ELISA) revealed that immunoglobulin A (IgA), IgM, and IgG were significantly higher in E group than in H group (p < 0.05). The hepatocytes of sheep fed xylanase diet showed arranged radially into hepatic plates cantered around the central vein, and the plates linked with each other to form a lost-like structure. A total of 4,509 differential genes (DEGs) were identified, among which 4,427 were up-regulated and 82 down-regulated. Additionally, the expression of antioxidant-related genes in cluding catalase (CAT), superoxide dismutase 1 (SOD1), oxidation resistance 1 (OXR1) and glutathione peroxidase 2 (GPX2), and immunity-related gene including mitogen-activated protein kinase 1 (MAPK1), signal transducer and activator of transcription 5B (STAT5B), janus kinase 3 (JAK3) and jun proto-oncogene (JUN) were verified using the quantitative reverse transcription polymerase chain reaction (qRT-PCR). Conclusion: In conclusion, dietary 0.2% xylanase supplementation promoted hepatic antioxidant capacity and immune response via modulating the expression of functional genes in Tibetan sheep.