Postprandial pattern of digestive enzymes and protein turnover in meagre (Argyrosomus regius) juveniles.

Abstract

After a meal, a sequence of physiological changes occurs in animals in response to digestion, absorption and assimilation of the ingested nutrients. These processes are very important for the aquaculture sector since they will define the efficiency by which food is converted into growth, thus contributing to reduce the production costs and also undigested food in the effluents. Here we investigated the activity of digestive enzymes in the midgut and the protein degradation systems following a single meal to define postprandial patterns of action in hepatic and muscle tissues of meagre juveniles. Fish were fed with a single meal followed by a period of 24h without feed. The activity of several digestive enzymes (α-amylase, trypsin, aminopeptidase, alkaline and acid phosphatases) plus the analysis of key players of the ubiquitin-proteasome (UPS) and autophagy-lysosomal (ALS) systems were examined just before feeding (0h, basal point) and 2, 4, 6, 8 and 24h after food ingestion. Digestion was activated around 4h after food ingestion and nutrients available for protein degradation 2h later. This work provided information about the short-term physiological effects induced by a single meal to support scientists' decision when planning a specific study involving digestion and protein degradation, and also to fish farmers on how to better manage feeding protocols when producing A. regius juveniles. Our results suggested that meagre juveniles, under the experimental conditions used, can be fed every 4h, time when digestion starts, however further studies should be addressed to find the optimal feeding regime for this juvenile species.