ABSORPTION AND INCORPORATION OF DIETARY FREE AND PROTEIN-BOUND ((UC)-C-14)-LYSINE IN ATLANTIC COD (GADUS-MORHUA)

Atlantic cod (Gadus morhua) were fed (U-C-14) lysine in an amino acid diet and (U-C-14) lysine bound into an intact protein to study the retention and metabolism of lysine. Fish fed the amino acid diet showed both earlier and higher maximum isotope activity in plasma as compared with fish fed the intact protein diet. Despite the lower values in plasma, the fish fed the intact protein diet showed the greatest retention of lysine in muscle tissue. Fish fed intact protein diet showed a maximum incorporation of 38.4% of the fed isotope into muscle at 24-48 hr postprandially. Those fed the amino acid diet reached a maximum level rat 24 hr postprandially with isotope incorporation of 30.4%. Incorporation into the myosin heavy chain was higher in cod fed the intact protein diet as compared with those fed the amino acid diet. The metabolism of lysine into fat was low.