Artemia protein is processed very fast in Solea senegalensis larvae: A dynamic simulation model

Abstract

Further improvement of growth performance in fish larviculture is closely linked to better understanding of the dietary amino acid (AA) requirements, and therefore of the processes involved in AA metabolism. In recent years, major advances in the understanding of fish larvae amino acid metabolism have been accomplished, in particular through the use of tracer studies. Modelling is a holistic approach to integrate knowledge on growth and metabolism and identify gaps in current understanding. A dynamic mechanistic model that simulates AA metabolism of fish larvae was developed. It aims to improve the understanding of larval digestion and absorption of dietary AA, and the postprandial AA metabolism and growth. The model also assists in the interpretation of results obtained from tracer studies. The model is driven by amino acid intake, with the absorbed dietary AA being used for energy production or for biosynthetic processes. The model is implemented for Senegalese sole (Solea senegalensis) larvae fed Artemia, and was parameterized using literature data. The model allows to integrate the results obtained after feeding a single meal with tracer AA, and following these tracer AA in the free AA and protein pools of larval gut and larval body at different time points after the meal. Model simulations suggest that there is a sharp dynamic change in the FAA pool after a meal while the protein pool is little affected. This suggests that the AA composition of the food has a major contribution to the FAA pool composition. This implies that sole larvae is highly sensitive to dietary AA imbalances, having high AA unavoidable losses unless the dietary AA profile is well balanced. The model also suggests that rates of protein synthesis and AA catabolism rapidly increases after the meal, with the peak for this postprandial metabolism occurring only 1h after the meal, and the rates returning to “basal” values 2h after the meal. This suggests a rapid processing of the Artemia protein by the larvae, and supports the need for feeding sole larvae at a high frequency in order to fully use its growth potential. Mechanistic modelling is useful and an important complement in evaluation of metabolism kinetics in nutrient flux studies. Moreover, due to its mechanistic nature, the present model can be used with different AA tracers, and also for other fish species.