Growth performance and acoustic feeding behavior of two size classes of Litopenaeus vannamei fed pelleted and extruded diets

This study aimed to compare the growth performance, food consumption, and acoustic feeding behavior of two size classes of Litopenaeus vannamei fed on extruded and pelleted diets. Two similar diets (35% crude protein) prepared by extrusion or pelletizing methods were offered to two shrimp size classes: small (3.83 ± 0.16 g) and large (10.28 ± 0.37 g). Shrimp were reared in 100-L aquaria (salinity 6 ppt, temperature 28 °C); growth performance and survival were analyzed at the end of 4 and 8 weeks for small and large size classes, respectively. Hydrophones recorded the sounds of shrimp feeding activity for 30-min intervals, after food remains were collected to evaluate consumption. Physical (pellet durability index, hardness, water absorption, density, sinking velocity, dry matter retention) and chemical (aromatic amino acids (AAA) leaching) characteristics of the diets were evaluated before and after soaking. Extruded diet presented higher durability and hardness before soaking, but its higher water absorption resulted in markedly texture softened and higher AAA leaching. Both shrimp size classes presented no significant differences in final mean weight, biomass, weight gain, survival, food conversion, and food consumption between pelleted or extruded diets. The mean acoustic energy did not differ between diets, but larger shrimp produced higher energy during feeding activity. The energy showed a significant progressive decrease along time intervals (10, 20, and 30 min) for both size classes and diets. Despite the different characteristics between pelleted and extruded diets, both resulted in similar shrimp performance and acoustic feeding profile activity under laboratory conditions.