To Standardise Parameters for Preparation of Extruded Feed Using Various Conventional and Non-Conventional Ingredients

The purpose of this research was to optimise extruder parameters for the preparation of floating fish diets with appropriate physicochemical qualities. The impact of temperature (90-120oC), moisture content (15%-30%), die diameter (2.0-4.0 mm) and pre-conditioning duration (15-30 m) on physical properties of the pellets such as bulk density, floatability, expansion ratio and water stability, were examined. Accordingly, four iso-nitrogenous (crude protein 35%) experimental diets were formulated for GIFT tilapia advance fry by replacing 50% of GNOC protein of the control diet (T0) by sunflower oilcake (SFOC) (T1), by linseed oilcake (LSOC) (T2) and by fish based silage (T3) protein. The pellets extruded using a combination of 120 oC extruder barrel temperature, 25% moisture content of feed mix, 2.0 mm die diameter and 30 minute of pre-conditioning duration gave most required pellet floatability (90-100%), expansion ratio (1.43-1.61), water stability (95-99%) and bulk density (0.8 - 0.9 g/cm3) for T1 and T2. However, fish silage when incorporated in the feed mix, it affected negatively in all the physical characteristics of a floating feed and resulted in higher bulk density and lower floatability, expansion ratio and also water stability.