Effects of dietary amino acid patterns on growth, feed utilization and hepatic IGF-I, TOR gene expression levels of hybrid grouper (Epinephelus fuscoguttatus ♀ x Epinephelus lanceolatus ♂) juveniles

A 7-week growth trial was conducted to evaluate effects of dietary amino acid patterns on growth, feed utilization and hepatic IGF-I, TOR genes expression levels of hybrid grouper (Epinephelus fuscoguttatus female x Epinephelus lanceolatus male) juveniles. Four isoenergetic (350 kcal per 100 g dry matter), isoproteic (53.5% of dry matter) and isolipidic (7% of dry matter) experimental diets were formulated with crystalline-amino acids (AAs) replacing approximately 42% fishmeal protein-bound nitrogen to,keep dietary AA patterns in line with the overall AA patterns of whole-egg protein (WEPAA), whole-body protein (WBPAA), muscle protein (MCPAA) of hybrid grouper and fishmeal (anchovy) protein (FMPAA), respectively. Each experimental diet was fed to triplicate groups of 15 hybrid grouper juveniles (average initial weight of 10.8 g/fish) which were stocked into small floating cages (L 120 cm x W 70 cm x H 50 cm). Experimental cages were labeled and located in four connective 6-m(3) indoor concrete tanks (L 3m x W2 mx H1 m) with 3 cages occurring in each tank. Weight gain (WG) of fish fed the FMPAA diet was significantly (P < 0.05) higher than that of fish fed the WEPAA diet or the WBPAA diet but did not significantly differ (P >= 0.05) from that of fish fed the MCPAA diet. Values of daily feed intake (NI) of fish fed the WEPAA diet or the WBPAA diet was significantly higher than that of fish fed the MCPAA diet or the FMPAA diet. Fish fed the FMPAA diet had significantly lower feed conversion ratios (FCRs), higher protein efficiency ratio (PER) and higher protein productive value (PPV) compared to fish fed other experimental diets. Whole-body protein content of fish fed the FMPAA diet was significantly higher than that of fish fed the WEPAA diet or the WBPAA diet. Muscle amino acid compositions were influenced by dietary amino acid pattern. Plasma total protein (TP) concentration of fish fed the FMPAA diet was significantly higher than that of fish fed the WEPAA diet or the WBPAA diet. The relative mRNA expression levels of insulin like growth factor-I (IGF-I) gene in liver of fish fed the FMPAA diet and the MCPAA diet were significantly higher than those of fish fed the WEPAA diet and the WBPAA diet. Fish fed the FMPAA diet showed significantly higher hepatic target of rapamycin (TOR) gene expression level than fish fed other experimental diets. Results of this study indicated that the amino acid pattern of fishmeal (anchovy) protein was more suitable as a reference amino acid pattern in diets of juvenile hybrid grouper compared to the amino acid pattern of whole-egg protein, whole-body protein or muscle protein of this fish species. (C) 2016 Elsevier B.V. All rights reserved.