EFFECT OF DIETARY SORGHUM DISTILLERY RESIDUE ON HEMATOLOGICAL CHARACTERISTICS OF CULTURED GREY MULLET (MUGIL CEPHALUS)—AN ANIMAL MODEL FOR PRESCREENING ANTIOXIDANT AND BLOOD THINNING ACTIVITIES

The sorghum distillery residue (SDR) has been an underutilized by‐product with estimated production of 150 ton/day in Kinmen, Taiwan. The objective of this study was to test for any physiological effects of SDR, thus to utilize it as a nutraceutical feed ingredient in diets for cultured fish. Hot air‐dried, wet, and dehulled‐wet sorghum distillery residue showed 63%, 90% and 97% inhibition of the hemoglobin‐catalyzed oxidation of linoleic acid compared to soybean (13%) and rice bran (78%). The feed formulated with 20% wet or dehulled‐wet sorghum distillery residue both showed an antioxidant activity of 68% being higher than the control diet (53%). Feeding these diets to cultured grey mullet for 60 days in summer (temperature ranged 24–30C), resulted in a lower hydroperoxide content in gill tissue, as shown by a chemiluminesence intensity of 1806 or 1409 mV as opposed to 2666 mV for fish fed a control diet. In winter, when the water temperature decreased to 14C, grey mullet fed a diet consisting of 10% dehulled wet sorghum distillery residue had a blood viscosity of 1.9 mPas and a hematocrit value of 33%, in contrast to 3.6 mPas and 41% for control. The blood of the control group started to aggregate in 6 h and showed hemolysis, while the mullet fed dehulled, wet sorghum distillery residue did not show blood aggregation, maintained normal fluidity and erythrocyte membrane integrity. It seems that cultured fish may have the potential as an animal model for prescreening antioxidant and blood thinning effects of food ingredients.