Performance and digestibility of inorganic phosphates in diets for juvenile shrimp (Litopenaeus vannamei): dicalcium phosphate, monocalcium phosphate, and monoammonium phosphate

Abstract

The suitability of feed phosphates for farmed shrimp was assessed in a trial for simultaneous determination of shrimp performance and digestibility. Juvenile shrimp (Litopenaeus vannamei) was reared during 52 days (individual weight from 5.5 to 16–20 g) fed plant-based diets supplemented with different sources of inorganic phosphates: dicalcium phosphate (DCP), monocalcium phosphate (MCP), and monoammonium phosphate (MAP). Test diets were formulated to contain similar levels of total phosphorus (0.75%, Ca/P ranging from 0.32 to 0.90). A (negative) control diet was tested with similar formulation devoid of inorganic phosphate supplementation (0.50% total P). Shrimp were reared in a clear water (34 ppt, 30 °C) recirculated tank system, stocked at a density of 82 individuals/m3, and fed continuously using a belt feeder. Feces were collected several times per day throughout the feeding trial. Mean survival ranged from 88% (control diet) to 95% (MAP diet) and did not differ significantly among treatments (P > 0.05). However, diet did affect feed consumption with highest daily feed intakes observed for shrimp fed the MAP diet, followed by MCP, DCP, and control. Not surprisingly, significantly higher growth was observed with shrimp fed MCP and MAP (2.01 and 2.10 g/week, respectively), compared with shrimp fed the control and DCP diets (P < 0.05). Feed efficiency (FCR) was also significantly reduced in shrimp fed MCP and MAP (1.66 and 1.59, respectively) compared with other treatments (P < 0.05). Moreover, shrimp fed MCP and MAP had significantly higher apparent digestibility coefficients (ADCs), including dry matter, crude protein, potassium, and phosphorus compared with shrimp fed the control and DCP diets (P < 0.05). Phosphorus content was also significantly reduced in feces of shrimp fed MAP (P < 0.05). Mineral content and retention efficiency in shrimp whole body and exoskeleton were also significantly higher with diets MCP and MAP compared with shrimp fed the control and DCP diets (P < 0.05).