Dietary Sea Buckthorn Polysaccharide Supplementation Enhances Antioxidant Capacity, Modulates Inflammatory Cytokines, and Alters the Serum Metabolome in Tumbler Pigeons

Sea buckthorn polysaccharide (SP) has antioxidant and anti-inflammatory activities, but its effects in tumbler pigeons remain unclear. Eighty-four male tumbler pigeons were assigned to four treatments receiving diets containing 0, 100, 200, or 400 mg/kg effective SP for 60 days, with seven replicate cages per treatment. SP supplementation enhanced serum antioxidant capacity and modulated inflammatory cytokine profiles, with the most pronounced overall responses observed at 200 mg/kg. The SP200 and SP400 groups also had lower serum lactate, total cholesterol, and triglyceride concentrations than the control group, whereas most blood gas, electrolyte, and acid–base variables were unaffected. Because SP200 produced the strongest antioxidant and cytokine responses, the CON and SP200 groups were selected for untargeted serum metabolomics. This analysis identified 68 and 79 differential metabolites in positive- and negative-ion modes, respectively. KEGG enrichment analysis ranked purine metabolism, phenylalanine metabolism, primary bile acid biosynthesis, and the citrate cycle among the leading pathways; however, none remained significant after Benjamini–Hochberg correction. Exploratory Spearman analysis revealed associations between selected metabolites and phenotypic indicators. Taken together, these findings indicate that 200 mg/kg SP may be an effective dietary supplementation level for improving antioxidant and inflammatory status in tumbler pigeons, while the associated metabolomic changes warrant further targeted validation.