EFFECT OF METHOD OF PROCESSING ON THE UTILIZATION OF DIETARY CARBOHYDRATE BY TILAPIA (Oreochromis niloticus)

Abstract

Several studies suggested that the use of hydrothermal treated carbohydrates in fish diets could improve their utilization by fish. In the present study, two methods of hydrothermal treatment (extrusion and cooking) were applied on raw yellow corn. In addition to a non hydrothermal method of processing (grain germination) was also studied. Then, the effects on feed utilization and growth performance of feeding tilapia (Oreochromis niloticus) different forms of processed corn were examined.

The present study was devided into two parts: Part 1: Effect of processing of raw yellow corn on its physical and chemical characteristic: A: Extrusion: Ground yellow corn was extruded at 90-95,100-105,110- 115,120-125 or 130-135 oc to produce five extruded corn products, E1, E2, E3, E4, and Es. respectively.

B: Cooking: Ground corn was boiled in water for 25 minutes to produce cooked corn 'C'.

C: Germination: Whole grains of yellow corn were germinated for 24,48 and 72 hours to produce three different types of germinating corn grains G24, G48 and Gn, respectively. Processed corn of the different types was then evaluated in relation to its chemical composition and physico-chemical characteristics (Gelatinization ratio 'GR', water absorption index 'WAI', water solubility index 'WSI'). The results could be summarized as follows: 1- Both extruded and cooked corn meal produced a gelatinized corn meal that has GR, WSI and WAI higher than those of raw corn.