Proper duration and intensity of feed deprivation promote a compensatory growth response in the ricefield eel, Monopterus albus

Abstract

Two trials were conducted with different durations and intensities of food deprivation to investigate the compensatory growth, food utilization and body composition of the ricefield eel, Monopterus albus. The different feeding protocols were tested for 64 days in two stages: experiment 1 comprised four levels of feed deprivation (1‐day starvation and one‐day refeeding (S1F1), 2‐day starvation and 2‐day‐ refeeding (S2F2), 4‐day starvation and 4‐day refeeding (S4F4), 8‐day starvation and 8‐day refeeding (S8F8)) and a control level (daily feeding). Experiment 2 comprised three levels of deprivation (1‐day starvation and 2‐day refeeding [S1F2], 1‐day starvation and 3‐day refeeding [S1F3], and 1‐day starvation and 4‐day refeeding [S1F4]). In experiment 1, the final body weight and specific growth rate (SGR) of the fish in all feed deprivation groups were significantly lower than those of the control; however, the feeding rate (FR) in all feed deprivation groups was significantly higher than that of the control. The feed efficiency (FE) in the feed deprivation groups was significantly lower than those of the control. In experiment 2, the final body weight and SGR in S1F3 and S1F4 approached the mean weight of the control. FR increased in S1F3 and S1F4, but FE did not differ among groups and was higher than in experiment 1, indicating that feed utilization efficiency increased with prolonged refeeding time. Overall, under the experimental conditions, feed restriction for 1 day followed by longer refeeding might represent an adequate management strategy in M. albus rearing.

Compensatory growth: Fitness cost in farmed fish and crustaceans

“…Studies carried out on the gilthead seabream (S. aurata) and the rice field eel (M. albus) showed a significantly lower lipid/lean mass ratio than the controls during refeeding, without displaying any compensatory growth response. 51,135 In addition, other fish exhibit compensation mechanisms whereas the lipid/lean mass ratio is not significantly different from the control 46,67 or was already normalised. 61,74 In view of the importance of the three energy resources (carbohydrates, lipids and proteins) during dietary restriction, a model considering these last three might be more accurate to explain the restoration of energy reserves during compensatory growth.…”

“…For example, in the fish Schizothorax wangchiachii and the shrimp P. vannamei, subjected, respectively, to 56 and 36 days of cyclic feeding restriction, final growth (full CG) and SGR showed no significant differences compared with their respective feeding controls. 34,49 In other cases, the cyclic feeding restriction could exceed the capacity to observe a full CG, as described in the fish Oreochromis mossambicus 50 and Monopterus albus 51 or in the shrimp Fenneropenaeus chinensis, 52 resulting in lower weight than control organisms and an averaged SGR lower than or equal to control ones. To determine the capacity of the CG response according to the employed feed restriction protocol, it is recommended to evaluate the SGR for specific periods.…”

“…Difficulty in achieving full compensation for fish or crustaceans under the most severe/longest restrictions could be explained by reaching the point of no return. If organisms accumulate too much stunted growth 24 or show alterations in physiological functions, particularly digestive functions, 46,51,82 the response of compensatory growth could be limited. According to Tian and Qin, 83 the point of no return is reached by fish showing a weight loss of 60% or more, beyond which full CG is no longer possible.…”

“…76 On the contrary, other studies have shown divergent results with the lipostat model. 51,61,67,80,122,135 Reasons for the disagreement with the lipostat model are diverse, and the implication of the lipid/lean mass ratio as an engine of compensatory growth has been questioned. Studies carried out on the gilthead seabream (S. aurata) and the rice field eel (M. albus) showed a significantly lower lipid/lean mass ratio than the controls during refeeding, without displaying any compensatory growth response.…”

“…In other cases, the cyclic feeding restriction could exceed the capacity to observe a full CG, as described in the fish Oreochromis mossambicus 50 and Monopterus albus 51 or in the shrimp Fenneropenaeus chinensis , 52 resulting in lower weight than control organisms and an averaged SGR lower than or equal to control ones. To determine the capacity of the CG response according to the employed feed restriction protocol, it is recommended to evaluate the SGR for specific periods 53,54 .…”