Salmon hydrolysate as a protein source for Atlantic salmon; prion content and effects on growth, digestibility and gut health

Abstract

Feeding unhydrolyzed protein to the same species from which it came from have caused prion disease in some mammals, but this has not been observed in fish. In this study, we characterized a salmon protein hydrolysate (FPH) for prion content and investigated how partially replacing fish meal with salmon hydrolysate, affected growth, digestibility and gut health of Atlantic salmon (Salmo salar). The salmon hydrolysate was analysed for prion content by shotgun and targeted proteomics, but no prions were found. Atlantic salmon post smolts were fed one of the following: a control diet containing 30% fish meal (FM), a 20% FM with 9% salmon hydrolysate diet (FPH-09) or a 10% FM with 18% salmon hydrolysate diet (FPH-18). Salmon fed the hydrolysate diets had higher specific growth rate over the first 25 days. The FPH-18 diet contained more digestible proteins and amino acids than the FM diet, and the ash digestibility increased linearly with the FPH content, indicating increased mineral uptake. Histological analysis of midgut and hindgut did not reveal any significant differences between the FM and FPH-18 diets, and the intestines were assessed to be normal and healthy. These results imply that salmon hydrolysate is a promising novel feed ingredient for Atlantic salmon, due to its excellent amino acid profile and high digestibility.