Biofloc Systems for Sustainable Production of Economically Important Aquatic Species: a review
Compensatory Growth and Productivity
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| 4. Compensatory Growth and Productivity
Throughout their life cycle, aquatic organisms experience a period of fasting, probably due to certain factors such as a periodically inadequate food supply, poor water quality, and the presence of pathogens in their environment, which causes stress. In aquaculture, food restriction is considered stressful but this technique has been used to reduce operational costs as well as the concentration of organic matter, nitrogenous, and phosphorus wastes in effluent water [ 81 , 82 ]. Furthermore, when food is restored after a period of starvation, aquatic organisms exhibit a phase of accelerated growth, also known as compensatory growth, which is usually associated with increased weight gain [ 82 ]. It is worth noting that animals use tissue energy reserves such as lipids for the induction of compensatory growth and this depends on several factors such as the type of species, development stage, body size, food quality, and the duration of starvation [ 82 , 83 ]. Hence, compensatory growth is a form of an internal adjustment mechanism that assists animals in adjusting to environmental stress [ 82 ,
, 85 ]. Studies on feed restriction in BFT systems and its effect on the growth performance and productivity of crustaceans and fish have been conducted, and, below, we present research findings obtained from some of these studies. Kaya et al. [ 9 ] found high productivity indices in the establishment of speckled shrimp (Metapenaeus Monoceros, Fabricus) in a BFT system during 30 days of cultivation. The study was carried out with four different biofloc treatments and a control with a stocking density of 12 shrimp/0.24 m 2 , using feed restriction regimes that consisted of one day of Sustainability 2021, 13, 7255 8 of 15
starvation and varying days of feeding. Generally, all BFT treatments exhibited improved growth performance (final weight, weight gain, daily weight gain, specific growth rate, protein efficiency ratio, survival rate, and food conversion ratio), whole-body crude protein ratios, and ash contents. Likewise, histopathological examinations did not indicate any pathological findings. In another study, Lara et al. [ 86 ] investigated L. vannamei juveniles (1.14 ± 0.38 g) cultured in a BFT system with 21 days of artificial feed restriction and with 29 days of artificial feedback and found partial compensatory growth in the second period and enhanced survival (>95%), resulting in 24.79% savings on artificial feed application. Rocha et al. [ 87 ] found that 1-day repetitive feed restriction and 1-day feeding in L. vannamei (0.46 ± 0.18 g) juveniles led to partial compensatory growth as a result of enhanced feed conversion efficiency driven by increased enzyme activity. Correa et al. [ 88 ] also found 70% survival in Nile tilapia (O. niloticus, 4.78 ± 0.13 g)
juveniles reared in a BFT system subjected to four days of feeding and three days of feed deprivation. Moreover, the reduction in feed costs was 46.7% and the authors anticipated that this would result in a 3% increase in the farmer’s partial profit. Likewise, the authors observed that two days of feed deprivation and 4 days of refeeding resulted in a high feed consumption ratio, feed efficiency ratio, and protein efficiency ratio, hence indicating that feed deprivation in tilapia does not affect the growth performance of fish. Gallardo-Collí et al. [ 5 ] found that cyclic feeding based on 12 days of feed restriction and 36 days of feeding triggered a complete compensation in weight and restoration of energy reserves, with similar measures of productive performance observed compared to the control. Moreover, feed restriction did not affect the proximal composition.
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