Impact of dietary phosphorus on turbot bone mineral density and content

Fish are largely dependent on dietary phosphorus for skeletal development and mineralization. In aquaculture, commercial diets commonly have higher phosphorus concentration than the basal requirements in most fish species to ensure growth and prevent bone mineral disorders. Excessive phosphorus in feeds is harmful for metabolism and results in an increase of wastes in farm effluents, which impact aquatic ecosystems. Previous studies have shown that depletion/excess of dietary phosphorus cause skeletal malformations and reduced/enhanced mineralization in fish. There is scarce information on dietary phosphorus requirements for optimal bone mineralization in species with different types of bone (cellular vs. acellular bone), which is particularly relevant for sustainable aquaculture. Thus, the aim of our study was to analyse the effect of dietary phosphorus concentrations on bone mineralization of turbot, a demersal acellular-boned fish and valuable aquaculture species. Our results show that the dietary phosphorus concentration did not cause changes to the bone mineral density and the phosphate/calcium concentrations. No apparent skeletal malformations were detected. Additionally, we did not find an altered expression of genes involved in bone mineral metabolism. Taken together, our data show that the phosphorus requirements for optimum growth and bone mineralization in turbot are below those currently used commercially at least for the time period examined: 55–195 days postfertilization (dpf).