DYNAMICS OF PLASMA-FREE AMINO-ACIDS IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) UNDER VARIETY OF DIETARY CONDITIONS

Plasma amino acid profiles in the systemic circulation of rainbow trou t acclimated to diets containing different protein sources, with and w ithout supplementation with free amino acids, were monitored for up to 120 hours after consumption of the diets. Plasma concentrations of ly sine, methionine, and isoleucine increased more rapidly after feeding a diet supplemented with these amino acids in free form and, depending upon the increase in plasma concentration, remained at concentrations above those in fish fed the basal diet for at least 24h after feeding . Dietary supplementation with isoleucine increased plasma concentrati ons of leucine and valine as well as of isoleucine. Maximum plasma con centrations for most amino acids were attained between 12 and 24h post prandial. Dietary inclusion of gelatin caused more rapid elevations in plasma glycine and serine than did free glycine. Feeding at three hou r intervals resulted in stable plasma concentrations of individual ami no acids in contrast to the fluctuations occurring when fish were fed once daily. Frequent feeding favoured a higher proportion of protein t o lipid in body composition.