Aquaculture Reports (Aug 2024)
Effects of protein sources and extrusion processing conditions via pellet physical quality on the feed intake, gastrointestinal emptying and digestion of spotted seabass (Lateolabrax maculatus)
Abstract
The diversification of future aquaculture feed formulas is expected to rise due to the increasing fish feed production. Changes in formulas and the corresponding adjustments to processing parameters can create variations in the pellet physical quality (PPQ). Despite these potential changes in PPQ, the impact of varying PPQ on the physiological response of fish is often undervalued or overlooked. In this study, we investigated the effect of protein sources and extrusion processing conditions through PPQ on the gastrointestinal chyme emptying, feed intake and digestibility of spotted seabass. Four diets were formulated following a 2×2 factorial design, with two protein sources (fish meal [FM] and cottonseed protein concentrate [CPC]) and two processing conditions (PC-M, preconditioning water content 30 % and die temperature 120 °C vs. PC-H, preconditioning water content 22 % and die temperature 140 °C). Fish (46 g) were fed twice daily to apparent satiation. Feed intake, nutrient digestibility and fish performance were evaluated over a 20-day experimental period. At the end of the experiment, chyme was collected after fish were fed restrictively one meal (0.95 % BW/d) to determine gastrointestinal emptying and water fluxes. Chyme was quantitatively collected from stomach and intestine at 2, 4, 6, 8, 12 and 24 h postprandial. Altering protein source affected PPQ as well as nutrient digestibility. Compared to FM-pellets, CPC-pellet lowered nutrients and energy digestibility. In addition, CPC-pellets led to a decrease in postprandial plasma glucose level and hepatosomatic index than FM-pellets. Processing conditions steered PPQ and influenced the physiological response of fish. PC-M resulted in a 23 % increase in stomach water flux at 4 h postprandial and a 2 % rise in stomach chyme water content than PC-H. Moreover, PC-H led to higher protein and fat digestibility than PC-M. Both protein source and processing condition treatments did not differ in feed intake, gastric emptying of fish.
