ARS | Publication request: The effect of feeding level on growth performance and indices of protein degradation in rainbow trout (Oncorhychus mykiss)

Submitted to: Aquaculture America Conference
Publication Type: Abstract Only
Publication Acceptance Date: December 1, 2010
Publication Date: March 3, 2011
Citation: Cleveland, B.M. 2011. The effect of feeding level on growth performance and indices of protein degradation in rainbow trout (Oncorhychus mykiss). Aquaculture America Conference. 51.

Technical Abstract: In rainbow trout the relationship between feed intake and feed efficiency is often determined as quadratic, with optimal feed efficiency (FE) occurring at moderate levels of feed restriction. However, it is not clear how levels of feed intake approaching satiation reduce FE through the regulation of mechanisms that affect nutrient utilization. Of particular interest are mechanisms that regulate proteolysis, since previous studies suggest that optimal FE is largely achieved by decreased protein degradation, rather than increased protein synthesis. Better understanding the correlations between FE and protein metabolism will provide insight into how FE is affected by feeding strategies via effects on protein degradation. In the present study rainbow trout were fed for 10 weeks at various levels of feed intake and indices of growth performance and protein degradation were determined. While the correlation between weight gain and feed intake was linear (P<0.001), the correlation between feed efficiency (FE) and feed intake was quadratic (P<0.003), with maximal FE calculated to occur at 76% of satiation. A quadratic relationship between feed intake and plasma insulin-like growth factor-I (IGF-I) (p<0.001) suggests that reduced concentrations of IGF-I during maximum feed intake may contribute to reduced FE. Similar effects on proteolytic gene expression in muscle implies that increases in protein degradation, mediated by reductions in IGF-I concentrations, may be a mechanism contributing to reduced FE during satiation feeding. Negative correlations between individual plasma IGF-I concentrations and atrogin-1 (P<0.001) and MuRF-1 (P<0.002) expression in muscle support this concept.