Effects of rice stored for six years on the nutritional value and physical quality of extruded feed for spotted seabass (Lateolabrax maculatus)

Long-term storage deteriorates the nutritional and processing quality of rice, yet it remains suitable for use in animal feed. This study evaluated the effects of rice stored for six years on the nutritional value and physical quality of aquafeed produced under different extrusion conditions. Fresh broken rice, which is widely used in animal feed, served as the control. The nutrient composition and pasting properties of fresh broken rice and rice stored for six years were analysed. Both rice sources had comparable protein, fat, starch, amylose/amylopectin ratio, and resistant starch contents. However, stored rice exhibited lower peak and breakdown viscosities, but a higher pasting temperature than fresh broken rice. Following this analysis, four isonitrogenous and isoenergetic diets were produced according to a 2 × 2 factorial design, using two formulas differing only in rice sources (fresh vs. stored) and two processing conditions (mild vs. harsh). Both formulas had an identical ingredient composition but included either 200 g/kg fresh broken rice or stored rice. Mild processing involved a preconditioning of the mash with 29.5 % water and a die temperature of 115 °C, while harsh processing involved a preconditioning with 24.5 % water and a die temperature of 145 °C. The experimental diets were fed to spotted seabass ( Lateolabrax maculatus ; 16 g) to satiation twice daily for 8 weeks. At the end of the trial, gastrointestinal chyme and blood were collected at 2, 6, 12 and 24 h postprandial following a single restricted meal to analyze gastrointestinal emptying, lipase activity and plasma glucose level. Feed intake, nutrient digestibility and fish performance were also evaluated. Results showed that stored rice diets exhibited a nutrient composition and physical quality comparable to those of fresh broken rice diets. Moreover, stored rice diets resulted in nutrient digestibility, feed intake, feed utilization and fish growth similar to those of fresh broken rice diets. Mild processing enhanced pellet porosity, increased nutrient digestibility and lipase activity, and improved feed utilization and growth than harsh processing. Neither rice sources nor processing conditions affected gastrointestinal emptying or glucose levels. This study highlighted that long-term stored rice can be effectively used in extruded aquafeed under mild processing conditions. • Long-term stored rice exhibits similar nutrient composition but lower viscosity than fresh broken rice. • Long-term stored rice can be processed into floating extruded feed under mild processing. • Stored rice can be used in extruded aquafeed, achieving high nutrient digestibility and utilization under mild processing. • Utilizing globally stored long-term grain in aquafeed reduces feed-food competition and supports sustainable aquaculture.