Effects of dietary protein and lipid levels on growth performance, feed utilization and body composition of juvenile hybrid grouper, Epinephelus fuscoguttatus x E-lanceolatus

An 8-week feeding trial was conducted to evaluate the effects of varying dietary protein and lipid levels on growth, feed utilization, and body composition of brown-marbled grouper (Epinephelus fuscoguttatus) and giant grouper (Epinephelus lanceolatus) hybrid. Eight diets were formulated to contain four protein levels (40, 45, 50 and 55% crude protein) and two lipid levels (7 and 14% crude lipid). Seven hundred and twenty juvenile grouper averaging 2.55 +/- 0.10 g were randomly allotted to 24 cages (8 treatments in triplicate groups) and fed the test diets to apparent satiation three times a day. The results showed significant (P < 0.05) enhancement of weight gain and specific growth rate with increasing dietary protein from 40 to 50%, and a reduced growth was obtained by further increase of dietary protein to 55%. Increasing dietary lipid level from 7 to 14% did not significantly affect growth performance (P > 0.05). Feed efficiency was significantly improved by increasing dietary protein and lipid levels. Also, the results revealed the significant increase of protein efficiency ratio by increasing dietary lipid. Significant reduction in daily feed intake was observed by increment of dietary protein and lipid levels. Whole-body lipid content increased with increasing dietary lipid and inversely correlated with whole-body moisture content. Dietary protein, lipid, and their interaction had a significant effect on liver protein content. Significant changes in dorsal muscle and liver fatty acid compositions were observed by variation of dietary protein and lipid levels. According to these results, a diet containing 50% protein and 14% lipid with protein to energy ratio of 23.9 mg kJ(-1) is recommended for efficient growth of juvenile hybrid grouper. Statement of relevance This research work provides useful information for formulation of cost-effective and environment friendly feeds for hybrid grouper which is considered as a promising candidate for aquaculture. (C) 2015 Elsevier B.V. All rights reserved.