Utilization of H2SO4-hydrolysed phosphorous from herring bone by-products in feed for Atlantic salmon (Salmo salar) 0+ postsmolt

Summary

The utilization efficiency of phosphorus (P) hydrolysed from herring by-products in feed for Atlantic salmon 0+ postsmolt was studied. Seven diets were produced with a low P level (D1): 5 g soluble P/kg, with P hydrolysed from herring by-products (D2, D3, D4): 7, 9 and 11 g soluble P/kg, or blue whiting fish bone meal (D5): 9 g soluble P/kg, and with P from NaH2PO4 (D6, D7): 9 g soluble P/kg diet. Diet D7 was also added (NH4)2SO4. Fish fed D1 had significantly lower growth compared to D3, D5 and D7, morphological changes in bone consistent with low mineral contents, significantly reduced scale macromineral contents and changes in P markers, that is bone ALP and NaPi in pyloric caeca. The average P retention was 3.6 and 3.2 g P/kg weight gain, respectively, in D2–D7 and in D1. Fish fed D3, D5 and D6 showed similar growth, P digestibility, tissue mineralization, P retention and P excretion. The dietary P requirement in salmon was met between 5.1 and 7.4 g/kg soluble P (DM). This study shows that P hydrolysed from fish bones can be recycled and used as an efficient P source in feed for Atlantic salmon.