Phosphorus (P) is one of the most important macromineral for fish due to its role on the sustainability and metabolism of aquacultured species. Therefore, P quantitative requirement has been extensively studied in several fish species, except for Tambaqui which only a handful of studies has been reported. Therefore, this study aimed to determine the available phosphorus (AP) requirement for tambaqui during the grow-out phase using several biomarkers of P adequacy.
A total of 128 tambaqui (395g ± 20) were randomly assigned to 15 1000L tanks connected to a recirculating water system and fed diets containing graded AP levels in triplicate. Fish were fed for 180 days and growth performance, bone mineralization, carcass composition and serum biochemistry were evaluated.
No mortality or apparent signs of P deficiency were observed during the growth trial. Dietary AP levels did not affect growth performance, except for phosphorus utilization (Table 1), which decreased linearly. Bone mineralization increased with dietary AP levels (Fig 1), while the scale and whole-body mineralization were unaffected. Dietary AP levels affected serum biochemistry (P<0.05), but not serum P and triglycerides (P>0.05). Based on these findings, we concluded that tambaqui in this stage developed properly without dietary inorganic P supplementation to plant-based diets. A minimum of 4.1 g/kg is needed to maintain growth parameters but leads to higher adiposity. On the other hand, the AP requirement for maximizing bone mineralization was 10.3 g/kg diet. Additionally, the level of 6.17 g/kg AP seems to be sufficient to improve immune response parameters such as total serum proteins, lysozyme, and immunoglobulins, thereby influencing the fish’s resistance.
a This research was financially supported by Fundação de Amparo à Pesquisa do Estado de Goiás (FAPEG).