In vitro protein digestion, and growth of Atlantic salmon with different trypsin isozymes

Growth and in vitro digestion was examined in three iso-trypsin phenotypes (patterns 1, 2 and 2') of Atlantic salmon, Salmo salar. Fish grew equally well during the 128 day experiment irrespective of phenotype. At day 64 and 91, weight-specific growth rate of 2' phenotype animals were significantly lower (p < 0.05). At the end of the experiment, significant differences (p < 0.05) were noted between groups with respect to size. An in vitro method was used to examine protein digestion by the different trypsin phenotypes. Three fish meals (FM I > FM II > FM III) of high, medium and low quality, as defined by chemical analyses, were used. Phenotype 1 was able to differentiate between three fish meals ranking FM > FM II > FM III. In contrast, phenotypes 2 and 2' were not able to separate between meals. In vitro digestion efficiency was dependent upon the three salmon types, ranking phenotype 2 > 1 = 2'.