The role of energy composition of diet affects muscle programming and fiber recruitment, body composition, and growth trajectory in rainbow trout

Authors: Overturf, Kenneth - Ken; Barrows, Frederic; HARDY, RONALD - University Of Idaho; BREZAS, ANDREAS - University Of Idaho; DUMAS, ANDRE - Coastal Zones Research Institute Inc

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2016
Publication Date: 4/20/2016
Citation: Overturf, K.E., Barrows, F., Hardy, R., Brezas, A., Dumas, A. 2016. The role of energy composition of diet affects muscle programming and fiber recruitment, body composition, and growth trajectory in rainbow trout. Aquaculture. 457:1-14.

Interpretive Summary: Aquaculture nutritionists have been testing and improving dietary feed formulations for decades. In evaluating new dietary components and feed formulations the most common parameters used to determine how well the feed performs are weight gain, feed conversion ratio, and specific growth rates. The information gained from these three measurements will tell us how the animal converted the formulated feed to weight, but does not provide any information specifically how the animal is processing the feed and its potential conversion to muscle. Muscle is the primary economic commodity of aquaculture, as most fish species are not only sold as whole fish but also as fillets, bullets, or eviscerated products. This research paper looks to utilize the expression of metabolic and developmental genes in the liver and muscle, enzymatic activity of protein turnover pathways, proximate composition, and muscle histology to evaluate fish metabolism when they are reared on diets comprised of differing levels of protein and lipid, the primary dietary energy sources. This information was then used to generate mathematical models for the prediction of body composition and nutrition deposition when fish are fed diets comprised of varying ratios of protein and lipid. Our results will aid in the development of more efficient feed formulations for rainbow trout.

Technical Abstract: Increasing production feed efficiency in aquaculture requires not only knowing the available energy for certain dietary components but understanding how they are interactively processed. For most aquaculture production muscle growth is of high priority. Nutrigenomics is a promising discipline to augment traditional research approaches in efforts to understand nutrient utilization and improve aquaculture performance. 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 11.2g). The growth trajectory of trout fed the 43P:20L and 50P:15L diets were identical and higher than trout fed the 62P:6L diet. Body composition differed between treatments early in the experiment and continued throughout. Analysis of gene expression data correlated with other measured parameters, providing significant information in evaluating metabolic processing of the different diets. Simple models were developed to predict body lipid content and feed intake of growing trout. This study shows that feed intake of juvenile trout is a function of dietary protein level, not energy, to sustain protein deposition. Our results demonstrate that an increased proportion of small muscle fibers were found to be associated with the highest relative expression of Pax7 over time and increased lysosomal activity in fish fed the 43P:20L dietary treatment. This is the first study in vivo using fish to show that induction of autophagy supports hyperplasia. Furthermore, these results demonstrate that macronutrients are potent regulators of hyperplasia and hypertrophy, and provide new opportunities for nutrition research designed to program performance and flesh quality of organisms.