Protease activities, plasma free amino acids and insulin at different agesof Atlantic salmon (Salmo salar L.) with genetically different trypsin isozymes

We show significant relationships between digestion rate of dietary protein , absorption/transport rate of amino acids, and plasma insulin concentratio n. Digestion rate of dietary protein was indicated by protease activity rat io of trypsin to chymotrypsin in the pyloric caeca. Plasma total free amino acids and/or the ratio of essential to non-essential free amino acids indi cated absorption/transport rate of amino acids. These relationships are ass ociated with and likely to be primarily affected by genetic variation in th e expression of different isozymes of trypsin, a key enzyme for feed utiliz ation and growth, affecting digestion, absorption/transport rate of amino a cids and plasma insulin levels in Atlantic salmon (Salmo salar L.).