Effects of particle grind size in extruded diets on Pacific white shrimp Litopenaeus vannamei growth performance

Abstract There is limited information on the impact of particle grind size in extruded aquaculture diets. Hence, the purpose of this research was to evaluate the effect of extruded diets with different particle grind sizes, with 95% of particles being below, 100, 180, 325, 475, and 700 µm on shrimp growth performance. The diets were tested in two different systems: one in a biofloc system and one in a green water system. The shrimp in the biofloc trial were stocked at 0.4 ± 0.1 g (mean ± SD), and the green water system used larger shrimp, stocked at 4.30 ± 0.23 g (mean ± SD). Both trials were conducted for 8 weeks. There were no significant differences ( p < 0.05) among treatments in either trial for any of the growth parameters. Shrimps in the biofloc trial had a final mean weight that ranged from 17.03 to 18.51 g ( p = 0.5771) and FCR 1.37–1.46 ( p = 0.8627), and shrimps in the green water trial had a final mean weight that ranged from 28.2 to 29.4 g ( p = 0.362) and FCR 1.19–1.28 ( p = 0.2852). This suggests that across juvenile to adult shrimp that the feed particle grind size in extruded diets does not appear to have a major effect on the biological value of the feed. The extra processing time, specialized equipment needed, and energy cost to grind to small particle sizes may not be necessary for extruded shrimp diets. Hence, feed mill manufacturers may want to re-evaluate the justifications for grind specifications for shrimp diets, since the extrusion processing mitigates the need for intensive grinding prior to feed manufacture.