Mulberry Branch Extracts Enhance the Antioxidant Capacity of Broiler Breast Muscle by Activating the Nrf2 and Cytochrome P450 Signaling Pathway

Mulberry branch extracts (MBEs) have garnered significant attention as natural feed additives and antioxidants; however, their antioxidant properties in meat post-slaughter and their influence on muscle-related metabolic processes remain largely unexplored. Herein, we evaluated the effects of MBEs on the antioxidant capacity and metabolic processes of breast muscle in yellow-feather broilers by adding 0 g/kg, 1.5 g/kg, 3.0 g/kg, and 4.5 g/kg of MBEs to their diets. The results demonstrate that MBEs enhanced the activity of antioxidant enzymes in muscle tissue. Specifically, a real-time quantitative PCR analysis revealed that MBEs increased the expression of antioxidant enzyme genes in a dose-dependent manner, activated the Nrf2 signaling pathway, and upregulated the expression of the Nrf2 gene and its downstream targets at doses of up to 3.0 g/kg. Furthermore, the results of widely targeted metabolomics indicate that the dietary supplementation of MBEs changed the amino acid profile of the muscle, increasing the levels of amino acids and small peptides that contribute to antioxidant properties while reducing the contents of oxidized lipids and carnitine (C5:1) and partially reducing the content of lysophosphatidylcholine (LPC). Notably, at doses of up to 3 g/kg, the levels of five signature bile acids increased in correlation with the added dose. A KEGG analysis indicated that the differential metabolites were predominantly enriched in the metabolism of xenobiotics by cytochrome P450, suggesting that the function of MBEs may be associated with the expression of P450 enzymes. In summary, this study demonstrates that MBEs are effective, safe, and natural antioxidants, offering a viable solution to mitigating oxidative stress in the yellow-feather broiler farming industry and even in livestock farming.