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

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.