Protective Effects of Magnolol, Rutin, and Gallic Acid in Broilers Challenged with Dietary Oxidized Soybean Oil

This study evaluated the protective effects of magnolol, rutin, and gallic acid in broilers fed oxidized soybean oil. Four hundred seven-day-old male Arbor Acre broilers were randomly assigned to five treatments with eight replicates each: CON (4% fresh oil), OOC (4% oxidized oil), and OOC supplemented with 200 mg/kg of magnolol (MAG), rutin (RUT), or gallic acid (GAA). OOC significantly reduced 42-day body weight (BW), average daily gain (ADG), and average daily feed intake (ADFI), reduced serum antioxidant enzyme activities (T-SOD, GSH-Px) and elevated malondialdehyde and triglyceride levels. It also upregulated hepatic lipogenic (FASN, ACACA, SREBP-1) and inflammation (NF-κB1/2) genes, damaged intestinal morphology, reduced cecal Erysipelatoclostridium and Shuttleworthia abundances, and elevated oxidized lipids (9,10-DiHOME and prostaglandin G2) in breast muscle. All three polyphenols increased ADFI (22–42 d), ileal villus height and ZO-1 expression, while reducing serum triglycerides, ileal MDA, and hepatic NF-κB2 expression. Both magnolol and rutin further enhanced BW (42 d) and ADG (7–42 d), decreased ACACA expression, and elevated cecal Lachnoclostridium abundance. Additionally, magnolol significantly decreased the contents of 9,10-DiHOME and malondialdehyde, while rutin reduced prostaglandin G2 levels in the breast muscle. In conclusion, polyphenol supplementation alleviated oxidized oil-induced adverse effects, with magnolol and rutin being more effective.