The Pacific white shrimp, Penaeus vannamei, is one of the most economically valuable aquaculture species and the most widely farmed crustacean in the world. Expansion of aquaculture industry requires the implementation of strategies to reduce production costs. Among these, feed restriction is gaining interest due to the unusual acceleration of growth after a feed deprivation period, known as compensatory growth. While compensatory growth may allow reaching the weight of organisms never subjected to dietary restriction, the associated physiological costs are poorly studied, particularly in crustaceans.
A 52-day trial was conducted on juvenile P. vannamei (0.5 ± 0.02 g avg. wt.), exposed to three different dietary regimes: three cycles of 3 days of feed restriction and 3 of feed ad libitum (T3:3), four cycles of 3 days of feed restriction and 9 of feed ad libitum (T3:9), and an unrestricted treatment as control. Each treatment consisted of 3 replicates of 95 shrimp in 600-L tanks. Following the cyclic feed restrictions, all shrimp were fed ad libitum. Intensity of feed restriction was calculated to allow a 20% saving of feed over the experimental period for both restricted treatments. On day 35 (during compensatory response), hepatopancreas and muscle samples were collected. On the same day, 16 shrimp from each replicate were extracted and subjected to two abiotic challenges. Eight shrimp were subjected to 24-hour hyperthermia (32°C). The other 8 shrimp were subjected to an increase in ammonium concentration for 24 hours (40 mg L-1). At the end of the abiotic challenges, hepatopancreas and muscle samples were collected.
After feeding restriction periods, T3:3 and T3:9, shrimp exhibited a lower weight than control organisms. On the final day, T3:3 reached a weight not significantly different from the control, showing full compensatory growth. T3:9 organisms were unable to reach the weight of the control organisms, however, they exhibited a significantly higher specific growth rate than the control during refeeding, indicating partial compensatory growth (Figure 1
At day 35, shrimp under compensatory growth showed lower hepatopancreas superoxide dismutase (SOD) activity than the control. Organisms’ survival during the abiotic challenges was not affected by the different treatments. After the abiotic challenge, shrimp in compensatory growth showed a significantly lower hepatopancreas SOD activity than the control (Figure 2). Compensatory growth was related to altered antioxidant activity in P.vannamei, however, lipid peroxidation, the main consequence of oxidative stress, was not significantly affected between treatments