Abstract: An initial investigation into the inclusion of Soy White Flakes (SWF) and High Protein Distillers Dried Grains (HP-DDG) in catla (Catla catla) diet, belonging to the family Cyprinidae was conducted using a single screw extruder. Particular focus was given to the effect of SWF inclusion and extrusion processing variables on the physical properties of the extrudates. To investigate this, 3 isocaloric (302 kcal/100 g) ingredient blends containing graded levels of SWF in combination with HP-DDG and other required ingredients were formulated to contain a net protein content of 31.5% (wet basis, wb). Extrusion processing was then performed using 3 SWF contents (10, 20 and 30% db), 3 moisture contents (15, 25 and 35% db) and 3 barrel temperature gradients (45-110-110, 45-140-140 and 45-170-170°C) while the screw speed and die diameter were kept constant at 150 rpm and 3 mm. Effects of these variables on extrudate physical properties including: Color, pellet durability index, bulk density, Water Absorption Index (WAI), Water Solubility Index (WSI), unit density and expansion ratio were extensively analyzed. Changing the level of SWF from 10-30%, a significant increase in the value of WAI from 3.98-4.26 and unit density from 0.89-0.92 g cm^-3 but decrease in the value of expansion ratio from 1.17-1.13 were observed (α = 0.05). Increasing moisture content from 15-35% resulted in a 37.5% increase in WAI and 17-14% decrease in bulk density and WSI, respectively. As temperature increased from 110-170°C, WAI and WSI increased by 12.3-4.3%, respectively. But, it decreased bulk density by 12% and unit density by 28%.