Minimizing phosphorus (P) wastes is a key factor for environmental sustainability of freshwater aquaculture operations. A dynamic model was constructed to simulate P utilization in salmonid fish through digestion, body deposition and excretion into urine and faeces. Dietary P was classified into pools of bone P, phytate P, organic P, Ca monobasic/Na/K phosphate and Ca dibasic phosphate. Hydrolysis of P from Ca monobasic/Na/K phosphate and Ca dibasic phosphate pools was represented by linear equations, whereas hydrolysis of P from bone P, phytate P and organic P pools was simulated by Michaelis-Menten equations. The available P pool was the sink for these hydrolysed portions. Absorption from the available P pool was simulated by passive and active uptake of P into the blood pool. Indigestible and unabsorbed P was excreted through faeces. Clearance of blood P was simulated by deposition into bone and soft tissues, excretion through urine as well as endogenous secretion into faeces. Bone deposition and soft tissue deposition in relation to blood P concentration were represented by Michaelis-Menten equations. Urinary excretion was the difference between glomerular filtration and saturable tubular reabsorption and was regulated by blood P concentration. The model was made dynamic by incorporating a body weight (BW) growth function. Response analysis was performed for fish weighing between 50 and 500 g, and the model responded appropriately to dietary P sources and levels. Retention of P ranged from 25% to 28% of intake for a prototypical commercial feed containing 1.15% dietary P. The model was also tested for parameter sensitivity. The most sensitive parameters were those related to body deposition and urinary excretion. This model can be used to simulate the effects of different dietary P sources and levels on P digestibility, retention, solid waste output (faecal excretion) and soluble waste output (urinary excretion). It could be useful for formulating strategies to improve production efficiency and reduce waste output.
|Title of host publication||Nutrient digestion and utilization in farm animals: modelling approaches.|
|Editors||E. Kebreab, J. Dijkstra, A. Bannink, W.J.J. Gerrits, J. France|
|Number of pages||12|
|Publication status||Published - 2006|
Hua, K., Cant, J. P., & Bureau, D. P. (2006). Dynamic simulation of phosphorus utilization in salmonid fish. In E. Kebreab, J. Dijkstra, A. Bannink, W. J. J. Gerrits, & J. France (Eds.), Nutrient digestion and utilization in farm animals: modelling approaches. (pp. 180-191). CABI. https://doi.org/10.1079/9781845930059.0180