Artificial diet alters the temporal patterns of postprandial digestion and hepatic metabolism in mandarin fish (Siniperca chuatsi)

Artificial diet slowed early evacuation yet hastened overall gastric emptying. • The artificial diet group had markedly elevated digestive enzyme activities. • Fish fed artificial diet showed early immune responses, then metabolic shifts. Postprandial digestion and metabolism are fundamental to understanding how mandarin fish ( Siniperca chuatsi ) respond to artificial diets. However, whether artificial diets alter the temporal patterns of postprandial digestion and metabolism within a single feeding cycle remains unclear. In this study, fish fed live prey (L) or an artificial diet (A) were sampled at 0, 3, 6, 9, 12, 18, and 24 h postprandially to evaluate gastric evacuation, digestive activity, and blood biochemical parameters, while hepatic transcriptomic responses were analyzed at 0, 3, 12, and 24 h. Gastric evacuation in both groups followed a square-root model, but exhibited markedly different patterns. During the early postprandial phase, the L group showed a progressive reduction in stomach contents, whereas the A group exhibited a transient increase in stomach wet weight; thereafter, stomach contents declined in both groups, with model-estimated complete evacuation occurring earlier in the A group. The A group showed elevated digestive enzyme activity, particularly α-amylase, and a faster and sustained increase in blood glucose. During the early postprandial phase, energy metabolism pathways, including oxidative phosphorylation, glycolysis/gluconeogenesis, pyruvate metabolism, and fatty acid metabolism, were more prominent in the L group, whereas immune-related pathways were more prominent in the A group; at later stages, glucose and lipid metabolism, PPAR signaling, and protein turnover became prominent in the A group. Collectively, artificial diets reshape postprandial physiology in mandarin fish. These findings provide a dynamic physiological perspective on the adaptation of mandarin fish to formulated feed. Download: Download high-res image (170KB) Download: Download full-size image