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Terrestrial plants as alternative protein source for juvenile turbot diet

Alternative feeds using proteins from terrestrial plants or animals can partially replace fishmeal in juvenile turbot in RAS but concessions may be needed.

In an experiment on juvenile turbot, all diets showed similar growth performance. Two experimental diets had fishmeal contained in control replaced with either 20 percent terrestrial plant proteins (PLANT) and processed animal proteins (PAP). Feed performance was significantly reduced in the PAP group.

“The present results of growth performance indicate that alternative feed formulations can be used in commercial aquaculture for juvenile turbot,” Christina Hoerterer et al. said in the study, “Sustainable fish feeds: potential of emerging protein sources in diets for juvenile turbot (Scophthalmus maximus) in RAS,” published on Aquaculture International.

When combining all feed performance indicators, the fish from the control group had the best performance followed by the PLANT group and the PAP group where fish showed the lowest performance,” they said.

The experimental feed formulations did not significantly affect the growth of the juvenile turbots, and there was zero mortality.

Together with nutritional value of feed formulation, the study also factored in the production costs. “Since feed costs are the largest cost factor in the production, small differences in the feed conversion ratio (FCR) can balance feed costs and could make more cost efficient formulations attractive,” they said.

The 16-week feed trial at the Alfred Wegener Institute Helmholtz Center for Polar and Marine Research in Germany, was conducted to find sustainable suitable replacement for commercial fishmeal in the diet of 20-gram juvenile turbot. The animal is known to have low tolerance to fishmeal replacements.

The study highlighted the suitability of alternative feed formulation of farmed fish. Included in PAP formulation were poultry meal and porcine hemoglobin. PLANT formulation had microalgae meals containing Arthrospisa platensis, Chlorella vulgaris and Tetraselmis chuii.

Putting the study’s FCRs into the equation showed that feed costs incurred to produce one ton of turbot is still lower in PAP formulation compared to the control and PLANT formulations. “Feeding juvenile turbot with the PAP formulation could lead to a cost reduction of 10 per cent compared to the control, whereas feeding the PLANT formulation would increase the costs by 12 per cent,” they cited.

The authors said that the alternative diet formulations may produce leaner fish. “Further studies on turbot in the grow-out phase will investigate how a higher fishmeal replacement will affect the performance.”