Energy composition of diet affects muscle fiber recruitment, body composition, and growth trajectory in rainbow trout (Oncorhynchus mykiss)

Abstract Increasing feed efficiency and muscle growth in aquaculture are of high priority and require understanding how dietary components are interactively processed and trigger molecular, tissue and whole-body responses. A 67-day trial was conducted to describe the effects of three feeds with varying dietary protein (P) to lipid (L) ratios (43P:20L, 50P:15L, 62P:6L) on growth trajectory, body composition, nutrient deposition, muscle histology, gene expression and protein degradation pathways of juvenile rainbow trout (initial weight 11.2 g). The growth trajectories of trout fed the 43P:20L and 50P:15L diets were identical and higher than trout fed the 62P:6L diet. The overall TGC was 0.261 for trout fed the 43P:20L and 50P:15L diets. Feed intake was associated with dietary protein level, not energy. Body composition differed among treatments early (at day 14) in the experiment and continued throughout. Body lipid and body protein contents varied significantly (P  − 1 ) compared to the 62P:6L (13.26 ± 0.66 mg (°C-d) − 1 ), but there was no significant difference with trout fed the 43P:20L diet (15.05 ± 0.69 mg (°C-d) − 1 ). This study demonstrates that macronutrients are potent regulators of muscle development and growth, and provides new opportunities in nutrigenomics to program performance and flesh quality of organisms. Statement of relevance Nutrigenomics can foster sustainable aquaculture.