Can Atlantic salmon (Salmo salar) grow on diets devoid of fish meal?

The present experiment tested whether Atlantic salmon accept, grow and utilise diets devoid of fish meal. Four diets were prepared, one reference diet in which 49% of the diet was fish meal and three diets not containing any fish meal. The amino acid composition in the test diets not containing fish meal was made similar to the reference diet by balancing with crystalline amino acids. All plant protein diets also contained 5% fish protein hydrolysate and, additionally, two diets were added with either stick water or squid hydrolysate in order to improve the palatability and thus feed acceptance. The experimental diets were fed to Atlantic salmon of 300 g body weight for a period of 3 months during which period no fish died. Fish fed the plant protein diets showed reduced feed intake as compared to fish fed the reference fish meal diet resulting in lower growth in the former. Feed conversion did not differ between treatments. Although the fish fed the fish meal diet showed higher growth than those fed the alternative three diets, protein accretion was not significantly different. In contrast, fat retention was significantly higher in the fishmeal treatment suggesting both a higher retention of dietary fat which was higher in the fish meal diet and a better utilisation of the dietary energy by salmon fed the vegetable diets due to a highly balanced dietary amino acid profile. The use of up to 10% crystalline amino acids in the diet increased the amino acid digestibility in the plant protein diets but utilisation of the dietary protein was not affected. The latter indicate that crystalline amino acids are utilised as well as protein bound amino acids at the level of 10% addition. Taking all together, particularly the diet containing squid hydrolysate might be an alternative to the fish meal diet in order to produce salmon.