Inorganic Phosphorus Supplementation in Diets for Farmed Shrimp: Performance and Digestibility of Juvenile Litopenaeus vannamei Fed Monosodium Phosphate, Monoammonium Phosphate, Magnesium Phosphate, and Monocalcium Phosphate

Abstract

Inorganic phosphates have been used in shrimp feeds to meet phosphorus (P) needs, which may be quantitatively affected by the dietary content of P and other minerals and digestibility. In the present study, performance and digestibility were determined simultaneously in juvenile shrimp (Litopenaeus vannamei) during the grow-out period (4–23 g ind wt). Shrimps were fed plant-based diets supplemented with different phosphate ingredients: monosodium phosphate (MSP), monoammonium phosphate (MAP), magnesium phosphate (MgP), and monocalcium phosphate (MCP). The total P level in test diets was 0.79%. MSP supplementation was tested at two dietary calcium:phosphorus ratios to check for possible effects upon shrimp performance and digestibility. A negative control diet was tested with a similar formulation without inorganic phosphate supplementation (0.47% total P). Shrimp was reared in a recirculated clear water tank system (35 ppt salinity, 30°C, 100 individuals/m³) with continuous feeding provided by automatic pellet delivery. Feces were sampled 4–5 times daily throughout the trial. A negative control diet produced P limitation and significantly reduced shrimp performances compared to P-supplemented diets (P  < 0.05). Performance of shrimp-fed diets containing inorganic phosphates varied for feed conversion rate: 1.24–1.34, survival: 87%–94%, growth: 2.50–2.59 g/week, and no significant difference was found among dietary treatments (P  > 0.05). Inorganic P supplementation resulted in significantly higher dry matter, crude protein, ash, and P apparent digestibility coefficient (ADC) compared to P limited negative control diet (P  < 0.05). In addition, reduced P ADC (P  < 0.05) was checked with higher dietary Ca:P ratio. Phosphorus digestibility in test diets showed significant differences: MSP > MCP, MgP, and MSP + CaCO₃; MAP > MSP + CaCO₃ (P  < 0.05). Digestible P (%) could then be calculated in test diets: MgP (4.77 g Pdig/kg of feed), MSP + CaCO₃ (4.81 g Pdig/kg of feed), MCP (5.0 g Pdig/kg of feed), MAP (5.13 g Pdig/kg of feed), and MSP (5.30 g Pdig/kg of feed). Digestible P in phosphate sources (%) could then be calculated: 88.2% MSP, 84.2% MAP, 79% MCP, 72.2% MgP, and 71.8% MSP + CaCO₃. Shrimp whole body and exoskeleton phosphorus content also showed significantly higher values in P-supplemented diets compared to control, regardless of the source tested (P  < 0.05). It is concluded that tested phosphates were suitable for feeding juvenile shrimp with MSP, MAP, and MgP diets showing high feed efficiency, while MSP and MAP diets resulted in numerically increased growth, coinciding with numerically higher P digestibility in these phosphates. The elevated P digestibility in the phosphates seems related to their water solubility, though MgP, less soluble and digestible in comparison to MSP and MAP, could also produce good performance.