A factorial approach to deriving dietary specifications and daily feed intake for mulloway, Argyrosomus japonicus, based on the requirements for digestible protein and energy

This study applied a factorial approach to predicting the requirements for digestible protein (DP) and digestible energy (DE) for mulloway throughout the production range. Published data relating to protein and energy utilisation and protein and energy requirements for maintenance and growth of this species were consolidated with quantitative descriptions of proximate whole body composition and an assessment of growth potential undertaken over a range of temperature and fish sizes. Factorial modelling of the data provided estimations of the decreasing requirement of the ratio of DP:DE for mulloway with increasing body size up to 2 kg. Piecewise regression analyses identified significant changes in the requirement for DP:DE at key growth stages. From this information diet specifications and suggested daily feed intake were iteratively derived applicable for the different dietary requirements dependant on body size. Four growth stages with corresponding dietary requirement for DP:DE are suggested; 10–100 g = 31.3 g DP MJ DE− 1 , 100–500 g = 24.8 g DP MJ DE− 1, 500–1100 g = 20.8 g DP MJ DE− 1, 1100–2000 g = 19.1 g DP MJ DE− 1. Sensitivity analyses was used to test the response of the factorial model to small perturbations of individual parameter values on the predicted optimal ratio of DP:DE. Protein and energy utilisation coefficients and the whole body composition coefficients for protein and energy were identified to have the greatest influence on the predicted requirement for DP:DE while the growth model exponent value becomes increasingly influential for fish > 200 g.