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

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.