A factorial growth and feed utilization model for barramundi, Lates calcarifer based on Australian production conditions

To optimize feeds and feed management for barramundi (Lates calcarifer), an improved factorial model is required. A growth function describing weight gain by barramundi as a function of fish weight and water temperature was derived from farm and laboratory data. The function was of the form: Gain (g fish(-1) day(-1)) = (K + xT + yT(2) + zT(3)) x (weight)(k). A maintenance energy demand function was also derived on a similar form and two functions combined to form the basis of a factorial model for this species. An assessment of protein and energy utilization efficiency was undertaken to examine the effect of fish size on the estimation of these parameters. Fish size had a significant effect on energy utilization efficiency on a linear basis, but no such difference was observed if the data were considered using non-linear methods. Protein utilization efficiency was also observed to be clearly non-linear, and although protein deposition capacity differed with fish size, the efficiencies of protein utilization were not affected. Using this factorial model, optimal iterative feed specifications were defined for a range of fish sizes and formulation constraints. A feed demand model was also developed based on the demand for digestible energy.