Simple SummaryIt has been widely reported that seaweed has numerous bioactive molecules that have been examined for health and growth-promoting effects. The current study was conducted to analyze the effects of various levels (starting from 0.25% to 1.25%) of brown seaweed and green seaweed on blood plasma antioxidant enzyme activities, hepatic antioxidant genes expression, blood plasma lipid profile, breast meat quality, and chemical composition in broiler chickens. The result showed that different levels of brown seaweed and green seaweed had no significant effects on broiler blood plasma catalase, superoxide dismutase, and glutathione peroxidase enzyme activities. In contrast, the hepatic superoxide dismutase 1 gene mRNA expression was significantly higher for birds fed 0.50% and 0.75% brown seaweed. Meanwhile, the total cholesterol and high-density lipoprotein levels were higher in blood plasma for birds fed 0.75 and 1% brown seaweed compared to the negative and positive control groups. The findings showed that different levels of brown seaweed and green seaweed had significantly higher breast meat crude protein content. The current research findings are useful for further studies to investigate the mechanisms and components responsible for affecting the hepatic antioxidant gene expression and blood plasma profile.AbstractThe study was designed to analyze the effects of brown seaweed (BS) and green seaweed (GS) on blood plasma antioxidant enzyme activities, hepatic antioxidant genes expression, blood plasma lipid profile, breast meat quality, and chemical composition in broiler chickens. The dietary treatment groups contained basal diet [negative control (NC)], basal diet + vitamin E (100 mg/kg feed) [positive control (PC)], basal diet + 0.25, 0.50, 0.75, 1, and 1.25% BS and GS supplements separately. The findings showed that both BS and GS exhibited remarkable antioxidant activity. In contrast, the maximum antioxidant activity was recorded by BS (55.19%), which was significantly higher than the GS (25.74%). Results showed that various levels of BS and GS had no significant effects on broiler blood plasma catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) enzyme activities. The hepatic superoxide dismutase 1 (SOD1) gene mRNA expression was significantly higher for birds fed 0.50% and 0.75% BS. Regarding the plasma lipid profile, the total cholesterol (TC) and high-density lipoprotein (HDL) levels were higher (p< 0.05) for birds fed 0.75 and 1% BS compared to the negative and positive control groups. The findings showed that different levels of BS and GS had significantly higher breast meat crude protein (CP) content.