Dietary phosphorus leaching and apparent phosphorus digestibility from different inorganic phosphorus sources for South African abalone (Haliotis midae L.)

The objective of this study was to determine phosphorus leaching of diets supplemented with various inorganic phosphorus sources [mono basic sodium phosphate (MSP), mono basic calcium phosphate (MCP), a 3 : 1 mixture of mono and dibasic calcium phosphate (MDCP), dibasic calcium phosphate (DCP)], and the apparent phosphorus digestibility of these sources in Haliotis midae. A trend of increased dietary phosphorus leaching from diet pellets with increased water solubility of sources was observed. MSP presented the highest (P < 0.05) phosphorus leaching (58.8%), while a value of 14.9% was obtained with DCP. Unexpectedly high phosphorus leaching (48.7% maximum) was obtained for a reference diet consisting of commercial feed ingredients (fish meal, soya bean meal, cottonseed meal) without any phosphorus supplementation. DCP presented a lower (P < 0.05) apparent phosphorus digestibility (27.9%) than MSP (66.5%), MCP (72.6%) and MDCP (66.3%). When dietary phosphorus leaching and apparent phosphorus digestibility were take into account, MDCP seems to be the most promising inorganic phosphorus source for inclusion in abalone diets. Further research should concentrate on minimizing dietary phosphorus leaching through feed preparation techniques.