The Effect And Mechanism Of Exercise Training On Growth Performance In Juvenile Spinibarbus Sinensis

Continual swimming exercise usually promotes growth in fish at a moderate water velocity. Five series of the experiment were conducted in juvenile Spinibarbus sinensis, one of the commercial fish species in the middle and upper reaches of the Yangtze River of China, at25±0.5℃, In experiment Ⅰ, the growth performance and postprandial metabolic response were examined after exhaustive chasing training once daily for21days in juvenile S. sinensis. In experiment Ⅱ, the growth performance and postprandial metabolic response were examined after aerobic exercise training20hours daily for56days at a water velocities of control (3cm/s),1,2and4body length (bl)/s in juvenile S. sinensis. In experiment Ⅲ, the effects of aerobic exercise training on the gut evacuation characteristics and digestive enzyme activities were examined in juvenile S. sinensis. In experiment Ⅳ, the effects of aerobic exercise training on the muscle structure and texture properties were investigated in juvenile S. sinensis. In experiment V, the effects of aerobic exercise training on the nutritional components were assessed in juvenile S. sinensis. The objectives of this study are to (1) determine the optimal water velocity for growth in juvenile S. sinensis,(2) investigate the mechanism of exercise training on growth performance in juvenile S. sinensis,(3) reveal the underlying regulation mechanism of fish feeding metabolism,(4) enrich related theory about the physiological ecology of fish and (5) provide practical information for application of running water fish culture and fishery enhancement and release. The main results of present study as follows:(1) Exhaustive chasing training resulted in significant decrease in feed intake, feed efficiency, weight specific growth rate, length specific growth rate, the peak metabolic rates, the energy expended on specific dynamic action (SDA) and SDA coefficients compared with those of control group in juvenile S. sinensis (P<0.05). Resting metabolic rates, times of peak metabolic rate and durations of SDA were not significantly different between control and trained groups in juvenile S. sinensis.(2) Aerobic exercise training induced a significant increase in feed intake compared with the control group, while the feed efficiency of the4bl/s group was significantly lower than that of the other three groups in juvenile S. sinensis (P<0.05). The1and2bl/s groups showed a significantly higher weight specific growth rate over the control group in juvenile S. sinensis (P<0.05). The resting metabolic rates and peak metabolic rates in the three training groups were significantly higher than that in the control group (P<0.05) in juvenile S. sinensis. Times of peak metabolic rate was significantly shorter in the1,2and4bl/s training groups compared with the control group, while exercise training showed no effect on SDA duration, factorial metabolic scope, energy expended on SDA and the SDA coefficient when compared to the control group in juvenile S. sinensis.(3) As postprandial time increased, the gut evacuation showed a fast-to-slow change characteristic in all experimental groups. The best mathematical model fitted to gut evacuation data in juvenile S. sinensis was the square-root model. Gut evacuation rates of the1and2bl/s training groups were significantly higher than that of the control group, while gut evacuation times of the1and2bl/s training groups were significantly lower than that of the control group after aerobic exercise training (P<0.05). However, gut evacuation rate and duration were not significantly different between control and4bl/s trained group in juvenile S. sinensis. Aerobic exercise training elevated the activity of both trypsin and lipase in the hepatopancreas and intestinal tract of juvenile S. sinensis (P<0.05).(4) There were no significant differences in the diameter and density of red muscle fibre for the1and2bl/s training groups and those of control group. However, the diameter of red muscle fibre was significantly smaller in the4bl/s training groups as compared to the control group,while the density of red muscle fibre was significantly larger in the4bl/s training groups as compared to the control group (P<0.05). The change trend for the diameter and density of white muscle fibre was similar as that of red muscle fibre after aerobic exercise training in juvenile S. sinensis. The hardness, springiness, adhesiveness, chewiness, cohesivenss and resilience of the muscle exhibited an increase trend with the increase of water velocity. However, there was not significant difference in the colour of muscle between control and trained groups in juvenile S. sinensis. The pHs of muscle in three training groups were significantly higher than that of control group (P<0.05).(5) No significant differences in the moisture and ash contents were found among the different groups. The percentage of protein in the2bl/s training groups was significantly higher than the control group (P<0.05). However, the percentage of fat in the4bl/s training group was significantly lower than those of1and2bl/s training groups (P<0.05). The contents of total amino acid and essential amino acid in1and2bl/s training groups were significantly higher than respective values of control group (P<0.05). The content of total amino acid in4bl/s training group was significantly lower than that of control group (P<0.05). The contents of fatty acid in1and2bl/s training groups were not significantly different as compared to that of control group. However, The content of total n-6fatty acids in4bl/s training group was significantly lower than that of control group (P<0.05). The main conclusion as follows:(1) The lower growth rate might be induced by poor feed intake and feed efficiency after exhaustive chasing training for21d in juvenile S. sinensis.(2) The improvement of growth may be primarily due to an increase in the feed intake after long-term training in juvenile S. sinensis. The optimum water velocity for the growth of juvenile S. sinensis occurred at approximately2.4bl/s. The juvenile S. sinensis in the4bl/s training group might have allocated more energy from their increased food consumption to sustain swimming rather than growth.(3) The juvenile S. sinensis adopt different feeding metabolic adaptation strategies under the different regimes of exercise training. The maintaining of resting metabolic rate and reduction of peak metabolic rate have been found after exhaustive training in juvenile S. sinensis. The up-regulated resting metabolic rate and peak metabolic rate were induced by aerobic exercise training in juvenile S. sinensis.(4) There were no significant changes in the gut evacuation characteristic and best mathematical model under condition of aerobic exercise training in juvenile S. sinensis.(5) Aerobic exercise training boosted the activity of digestive enzymes and gut evacuation rate, which could favor fast digestion and growth at a moderate water velocity in juvenile S. sinensis.(6) Aerobic exercise training resulted in significant increase in muscle protein content at a moderate water velocity in juvenile S. sinensis. This finding may have resulted in an improvement of growth because it is possible that the increased growth rates resulted from the proportionately greater increase in the protein synthesis rate in trained fish.(7) Aerobic exercise training may be one of effective ways to improve flesh quality in S. sinensis due prolonged swimming at moderate water velocity could improve texture properties and nutritional components of muscle in juvenile S. sinensis.