The influence of dietary protein and fat levels on tissue free amino acid levels of fingerling rainbow ž / trout Oncorhynchus mykiss

The influence of six semi-purified diets having different nutrient composition on the tissue free Ž . amino acid FAA levels of fingerling rainbow trout was examined. Four balanced amino acid Ž . Ž Ž . Ž .. diets casein:gelatins6:1 with combinations of two protein levels 35% LP and 50% HP and Ž Ž . Ž .. Ž . Ž two fat levels 10% LF and 20% HF , and two imbalanced high-protein 50% diets IMB-HP, . Ž . Ž casein:gelatins1:1 with two fat levels LF and HF , were each fed to duplicate groups 30 . fishrgroup, 10 grfish for 6 weeks at 158C. FAA in plasma, liver, dorsal white muscle and brain at 12 h after the last feeding were compared. Percentage weight gain of the HPHF diet group was Ž . the highest, but was not different P)0.05 from the others except for the IMB-HPLF diet group Ž . P-0.05 . Levels of individual amino acids in the whole body protein were not markedly Ž . different among the treatments. Most of the free essential amino acid EAA levels in the tissues of the HP diet fed fish were higher than in those of the LP diet group. The levels of free phenylalanine and tyrosine of the HF group tended to be higher, and those of taurine lower, than the LF group. Most of the free EAA levels of the IMB diet group were lower even than the LP group. Correlations in EAA patterns between a given diet and tissue were high in plasma, but very ) Corresponding author. Tel.: q81-596-58-6411; fax: q81-596-58-6413; e-mail: [email protected] 0044-8486r00r$ see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0044-8486 99 00277-X ( ) T. Yamamoto et al.rAquaculture 182 2000 353–372 354 low in muscle and brain. These findings suggest that not only dietary protein level and amino acid profile, but also dietary fat level affects the levels of certain FAA of rainbow trout tissues. q 2000 Elsevier Science B.V. All rights reserved.