EVALUATING 4 DIFFERENT TYPES OF INORGANIC PHOSPHORUS SOURCES IN WHITELEG SHRIMP Litopenaeus vannamei

A study was undertaken to evaluate the effect of four supplemental phosphorus sources:  Windmill^® Aquaphos, Aliphos^® Dical (DCP), Aliphos^® Monocal (MCP) and monopotassium phosphate (MKP) on the performance, whole body phosphorus (P) and calcium (Ca) retention, P and Ca digestibility on white leg shrimp Litopenaeus vannamei.

Quadruplicate groups of 27 shrimp average weight 3.7 g, were fed one of the trial diets for 35 days (performance and retention trial). The second part of the trial involved duplicate groups of 20 shrimp average weight 13.5 g fed for 18 days (digestibility trial). At the start of the trial a pool of 10 shrimp from the initial stock and a pool of 10 shrimp per tank at the end of the trial were sampled for whole body analysis. To determine the digestibility, yttrium oxide was added to the experimental diets as an indigestible marker. Faeces were collected by means of syphoning. The trial was carried out using a RAS-system with a salinity of 20 ppt.

Final body weight (BW, g) ranged from 12.9 (DCP) and 13.6 (Aquaphos). Growth (g/w) and specific growth rate (SGR,%) were not significant different amongst the groups. Contrary to the feed conversion (FCR), which was the lowest for Aquaphos (0.90) and the highest for DCP and MKP (0.99).

The whole-body composition of shrimp in terms of protein, ash, Ca and P was affected by the dietary treatments. The retention of P (% of intake) was significantly higher for the Aquaphos group, resulting in a higher P-retention of the phosphorus source for Aquaphos (44%) compared to MKP (11.5%), MCP (16.5%)

and DCP (2.5%).

The digestibility of P (expressed as % of intake) showed significantly higher values for the MKP and Aquaphos group. This resulted in a significantly higher P-digestibility for both the phosphorus sources MKP (93%) and Aquaphos (79%).

Seeing the difference in P-retention and -digestibility of MKP, it was hypothesized that this different might be due to a higher leaching of P from MKP from the pellets and possibly faeces than in case of the other P-sources, including Aquaphos.