Effects of soybean isoflavone on growth performance, meat quality, and antioxidation in male broilers.

To investigate the effects of a synthetic soybean isoflavone (ISF) on growth performance, meat quality, and antioxidation in male broilers, 1,500 birds that were 42 d old were allotted to 5 treatments with 6 replicates per treatment (50 birds per replicate). Birds were fed diets supplemented with 0, 10, 20, 40, or 80 mg of ISF/kg, respectively, for a period of 3 wk ad libitum. The results showed that dietary supplementations with 10 or 20 mg of ISF/kg increased weight gain by 13.6 and 16.2% (P < 0.01) and elevated feed intake by 7.37% (P < 0.05) and 11.2% (P < 0.01), respectively. Addition of 10 mg of ISF/kg decreased feed:gain by 5.5% (P < 0.05). Supplementation with 40 mg of ISF/kg in the diet slightly increased water-holding capacity by 17.24% (P < 0.1), and the addition of 20 or 40 mg/kg of ISF significantly increased the pH value of meat (P < 0.01), although adding 40 or 80 mg of ISF/kg increased the lightness of meat color (P < 0.05). Malondialdehyde production was slightly reduced in plasma of 20 mg of ISF/kg supplemented chickens (P < 0.1) and significantly decreased in breast muscles of 20, 40, or 80 mg of ISF/kg supplemented chickens (P < 0.01). The addition of 40 or 80 mg of ISF/kg significantly increased total antioxidant capability (P < 0.01) and slightly elevated total superoxide dismutase activity (P < 0.1) in plasma of chickens. The dose of 80 mg of ISF/kg slightly improved catalase activity in plasma (P < 0.06). In breast muscle, treatment of birds with 40 or 80 mg of ISF/kg caused an increase of total superoxide dismutase activity by 25.36% (P < 0.05) or 63.93% (P < 0.01). Catalase activity significantly increased by 70.61% by the supplemental ISF at the 40-mg level (P < 0.05). Also, 10, 20, or 40 mg doses of ISF/kg decreased lactic acid production (P < 0.05). The results of this study indicate that dietary ISF could improve growth performance and meat quality by decreasing lipid peroxidation and improving antioxidative status in male broilers.