author(s)
Manmohan Kumar, Arun Bhai Patel, Naresh Raj Keer, Sagar C Mandal, Pradyut Biswas and Satyajit Das

abstract
A study was conducted to investigate the effects of graded replacement of dietary corn with tapioca starch on the physical properties of extruded fish feeds. Five (5) isonitrogenous fish feeds of 28% crude protein were formulated utilizing locally available feed ingredients wherein tapioca starch replaced corn starch at 0% (D1–Control), 25% (D2), 50% (D3), 75% (D4) and 100% (D5). The proximate compositions of the ingredients were determined and the physical properties of different extruded fish feeds were investigated. The results showed that replacement of corn starch with tapioca starch had significant effects (p<0.05) on physical properties of the extruded feeds. The significantly highest bulk density (BD) was observed for D1 (541.5 g L^-1) while the lowest BD observed in D5 (454.8 g L^-1). Significant differences (p<0.05) in water stability (WS) of extruded fish feed were evident both after 15 minutes and 30 minutes exposure to water with the highest values for D1 (89%) and D2 (84.9%), respectively. On the other hand, the lowest values were noted for D5 (85.9% and 80.5%) after both 15 minutes and 30 minutes of exposure to water, respectively. The result of the study revealed that replacement of corn with tapioca starch led to a significant but marginal reduction in BD and WS. Further, up to 50% replacement level no reduction in WS was noted.