Gastric evacuation and changes in postprandial blood biochemistry, digestive enzymes, and appetite-related genes in juvenile hybrid grouper (Epinephelus moara ♀ x E. lanceolatus ♂)

The proportion of remaining stomach meal (PSR), gastric evacuation model, serum cortisol and glucose levels, intestinal lipase, amylase, and chymotrypsin activities and the expression levels of neuropeptide Y (npy), orexin (ore) and leptins (lepa, lepb) of the hybrid grouper (Epinephelus moara female x E. lanceolatus male) during gastric evacuation were evaluated to determine the optimal feeding interval. Results showed that PSR significantly decreased by more than 60%, 70%, and 90% at postprandial 6 h, 9 h and 12 h, respectively. The cubic root curve was the most supported model and fitted all PSR data. The cortisol and glucose levels were significantly varied, and the highest values were obtained at postprandial 6 h. Cortisol and the glucose levels then gradually decreased from postprandial 9 h to postprandial 12 h. Intestinal lipase and chymotrypsin activities showed similar results to cortisol, whereas the amylase activity was not significantly different during gastric evacuation. The hypothalamic npy and ore mRNA levels were gradually up-regulated within postprandial 6 h, and then significantly down-regulated from postprandial 9 to postprandial 12 h. By contrast, hepatic lepa and lepb mRNA levels remained high levels within postprandial 6 h and significantly decreased from postprandial 9 to postprandial 12 h. These results indicated that food digestion in the intestine peaked at postprandial 6 h. Afterward, appetite returned and fully recovered at about postprandial 12 h. Therefore, on the basis of the aforementioned results and considering the fish management, postprandial 12 h is the optimal feeding interval of hybrid grouper (Epinephelus moara female x E. lanceolatus male). This feeding interval offers potential savings in time and labor spent in cultivating hybrid grouper in captivity.

Automated summary

The optimal feeding interval for hybrid grouper was determined to be postprandial 12 h, when food digestion peaked in the intestine and appetite recovered. This interval offers potential savings in time and labor for fish management and cultivation.