Proposal of a dynamic model as a tool to simulate growth performance and nitrogen release in rainbow trout Oncorhynchus mykiss farming

In order to verify the possibility to apply of European unio‎n methodology of calculating N balance in rainbow trout farms, a dynamic model was developed using StellaTM for the simulation of growth performance and nitrogen release (GPNR model). GPNR applied the thermal-unit growth coefficient to estimate biomass weight. Actual N release (ANR) was calculated as the difference between actual N allotted and N retained in biomass. Minimal N release (MinNR) and maximal N release (MaxNR) were estimated when actual N allotted was unknown. Datasets obtained by eight experiments of different feeding conditions and one field production were used to verify the suitability of the model on rainbow trout production. The results showed that GPNR can be used to simulate growth performance and N release at any time during the production cycle. ANR was within the range of MinNR and MaxNR when the ratio of digestible protein and digestible energy of the diet was less than 24.81 g/MJ. Daily maximal feed intake provides a yardstick for farmers in fish farming practice. GPNR model offers farmers and water authorities an useful and simple tool to maintain sustainable development of fish farming production and control N pollution in water.