PRODUCTION PERFORMANCE OF TAMBAQUI JUVENILES SUBJECTED TO SHORT FEED-DEPRIVATION AND REFEEDING CYCLES

Abstract

This study proposes to investigate whether short restricted-feeding cycles during the pre-fattening phase of tambaqui (Colossoma macropomum) juveniles affect their production performance and yield in a semi intensive system and if this practice can be introduced as an alternative to reduce production costs in the pre-fattening phase of this species. The fish (8.07 ± 0.07 g) were subjected to short restricted-feeding periods under controlled laboratory conditions (experimental boxes) for 60 days (Phase I). Three feeding strategies were tested, namely: dairy feeding (Control); five days of feeding followed by two days of deprivation (5F/2D); and two days of feeding followed by four days of deprivation (2F/4D). Subsequently, the fish from each treatment (feeding regimes) evaluated in Phase 1 were transferred to an excavated pond with low water exchange and no supplemental aeration (semi-intensive system) where they were fed continuously for 65 days (Phase II). At the end of both phases, performance, metabolic and hematological parameters and the centesimal composition of the filets were analyzed and an economic assessment was undertaken based on the total operating cost (TOC) of production in the different feeding regimes. The restricted-feeding cycles 2F/4D and 5F/2D (Phase I) affected the performance of the fish, which showed lower daily weight gains and specific growth rates (SGR), resulting in lower viscerosomatic index (VSI) and morphometric measurements. However, apparent feed conversion did not differ across the treatments. The feed-deprived fish used triglycerides as an energy source, maintaining their blood glucose levels close to those of the continuously fed group (control). When they started to be feed daily for 65 days (Phase II), the metabolic (triglycerides) and hematological parameters (hematocrit and hemoglobin) equaled those of control group. Nevertheless, their final weight and morphometric measurements were lower than those of non-restricted feed, indicating a partial compensatory growth in tambaqui juveniles. Short restricted-feeding cycles applied in the pre fattening phase for 60 days negatively affected performance and led to metabolic and hematological alterations in tambaqui (Colossoma macropomum) juveniles. Although these short restricted-feeding cycles resulted in less expenditure on labor and feeding, the fish under those conditions did not develop  equally to those fed daily, culminating in less biomass produced during the fattening period in a semi-intensive system for 65 days. Ultimately, this led to a higher total operating cost per gram  of produced fish, demonstrating the economic infeasibility of this practice for tambaqui juvenile production.