Extrusion Processing and Its Effect on Aquaculture Diet Quality and Shrimp Growth

Abstract

A wet extrusion process involving the use of shear, temperature, and moisture was evaluated in relation to diet quality and shrimp growth. Eighteen diets, consisting of two levels of shear, three levels of preconditioner discharge temperature, and three levels of ex-trudate moisture, were produced to determine their effects on starch gelatinization, pellet stability, and shrimp growth performance. Test organisms were juvenile Pacific white shrimp, Penaeus vannamei with an average size of 0.91 g. Shrimp were subjected to an 8-week indoor growth trial and were evaluated for live weight, weekly growth rate, feed conversion ratio (FCR), and survival. The results demonstrated that shear was the controlling factor in starch gelatinization, while moisture was the predominant factor on pellet stability and shrimp growth. Wet extruded diet with moisture content ranging from 20% to 35% had higher pellet water stability that favored shrimp growth and FCR. Shrimp live weight and weekly growth rate were highest at 29.5% extrudate moisture. This was achieved at 90 °C preconditioning temperature and high level of shear. Moisture, shear, and temperature did not show any significant effect on shrimp survival (P > 0.05). Moisture content of wet extrudate showed a dominant effect on pellet stability, shrimp growth, and feed utilization efficiency, while shear appeared to strongly influence starch gelatinization during the extrusion process. These findings may be useful in the optimization of wet extrusion process for the efficient production of high quality and high performance shrimp diets using similar extrusion conditions.