Growth, Survival, and Diet Utilization of Pacific White Shrimp, Penaeus vannamei, Fed Dry Extruded Diets with Different Levels of Shear and Moisture

ABSTRACT

A dry-extrusion process involving the use of shear and moisture was evaluated in relation to diet characteristics and shrimp biological performance. Nine diets, consisting of three levels of barrel-screw shear and three levels of extrudate moisture, were produced from an InstaPro 2500 extruder to determine their effects on starch gelati-nization, water stability, shrimp growth, survival, and feed conversion ratio. Juvenile Pacific white shrimp, Penaeus vannamei, with an average weight of 1.12 g were used in an eight-week indoor growth trial. The results demonstrated that shear was the controlling factor in starch gelatinization and water stability, while moisture was the predominant factor on shrimp growth. High shear, with temperature ranging from 134_C to 167_C, produced a high degree of starch gelatinization and high water stability. High moisture, ranging from 20% to 22%, produced the best growth in shrimp. The best performance for shrimp had a live weight of 5.94 g, weekly growth of 0.60 g, feed conversion ratio (FCR) of 1.55, and survival of 75%. This was achieved with diets having a relatively low starch gelatinization (73.5%) and low water stability (88.9%), which were processed at high moisture and low shear condition. Diets with high starch gelatinization and high water stability did not yield the best growth performance for shrimp, indicating that optimization of the dry extrusion process for desirable diet characteristics and shrimp performance is strongly recommended. Shrimp survival and FCR, however, were not significantly different among the effects of shear and moisture.

Key Words:

• Growth
• diets
• white shrimp
• extrusion process