Abstract:To investigate the diet feeding rhythm of juvenile of Thamnaconus septentrionalis and gastric emptying model, a once-per-day satiation feeding treatment (one day was divided into eight time periods, each time period was used as one treatment, and the fish of each treatment were fed to apparent satiation once a day) and a continuous feeding treatment with fixed intervals (one day was divided into eight time periods, the fish in each tank were fed to apparent satiation, eight times a day) were conducted for 7 days. The experimental fish [(4.28±0.46) g] were removed at various intervals (0, 2, 4, 6, 8, 10, 12, 14, 16, 20, 24, and 28 h) after satiation feeding. The wet mass of the chyme was determined and the applicability of the three mathematical models (linear model, exponential model, and square root model) was compared by the fitness of gastric evacuation data in juvenile T. septentrionalis. The results showed that T. septentrionalis exhibit a 24 h diet feeding cycle under two feeding scenarios. The feeding rate under the segmental continuous feeding mode was not significantly different at 03:00, 06:00, 09:00, and 12:00, but decreased rapidly after reaching a peak at 15:00 (P<0.05), and at 0: 00 reached the lowest value (P<0.05). The feed efficiency was not significantly different at 03:00, 06:00, 15:00, and 18:00 in the once-per-day satiation feeding, and the specific growth rate was significantly higher than that of a once-per-day satiation feeding (P<0.05). (2) The feeding rate of experimental fish decreased rapidly after 18:00 in the continuous feeding with a fixed interval (P<0.05), and reached the lowest value at 00:00 (P<0.05). The specific growth rate and feed efficiency at 09:00 and 12:00 in the experimental fish were significantly higher than at the other times of the day (P<0.05), optimal feeding times in T. septentrionalis culturing were during 15:00~18:00. (3) Among the three models, the gastric emptying rate was best fitted the square root model, and the equation was y0.5=2.802‒0.204t (R2=0.987). According to the square root model, the feed in the stomach was fed for 10 h. The left and right sides were completely emptied to the level before feeding, and the 80% gastric emptying time was 6 h. Based on the above indicators, it is recommended to feed the T. septentrionalis 3 times every day during the production practice from 09:00 to 15:00, with an interval of 3 h.
