Utilization of diets with hydrolyzed potato starch, or glucose by juvenile white sturgeon (Acipenser transmontanus), as affected by Maillard reaction during feed processing

An 8-week growth trial was conducted to study carbohydrate utilization by white sturgeon fed diets containing glucose or hydrolyzed potato starch (HPS). Four diets supplemented with 15% or 30% of glucose or HPS and a control diet with no added carbohydrate were each fed to triplicate groups of fish. The diets were processed by a 3-min 80 degrees C microwave moist heating, followed by 1-h 70 degrees C drying. Feeding rates varied from 1.7% to 3.2% body weight day(-1) so that all treatment groups were fed the same amount of dietary protein and lipid. The HPS groups showed the highest (P<0.05) specific growth rate, followed by the control, and then by the glucose groups. Feed efficiency was highest in the control and 15% HPS group followed by the 30% HPS group, and lowest in the glucose groups. Protein and energy retentions, whole body lipid, and muscle glycogen showed a similar pattern; with the glucose groups significantly lower than the control and HPS groups, whereas there was no difference among the control and HPS groups. A lower lysine and glucose in the glucose than control diets suggested that a severe Maillard reaction had occurred in the moist heat process, drying, and storage of the glucose diets. This is supported by the significantly lower plasma lysine concentrations in sturgeon fed the glucose diets than those fed the control diet. Sturgeon fed the glucose diets also showed significantly lower concentrations of plasma protein, cysteine, and hydroxyproline than those fed the control diet, whereas concentrations of liver glycogen and plasma alanine, gamma-aminobutyric acid and proline were significantly higher in sturgeon fed the glucose than the control and HPS diets. In conclusion, growth performances of sturgeon were not adversely affected by 15% HPS in the diet but severe Maillard reaction in the glucose diets resulted in significant reduction in the growth performances of the fish. (C) 2005 Elsevier B.V. All rights reserved