Effects of soybean and sunflower meals on the growth, feed utilization, and gene expression in two Canadian strains of juvenile Arctic charr (Salvelinus alpinus)

The effects of graded levels (0-20% total dietary inclusion) of commercial, solvent-extracted soybean meal (SBM) and expeller sunflower meal (SFM) were investigated on growth, nutrient utilization, and pro-inflammatory gene expression in the distal intestine and spleen of two commercial Canadian strains (Strain 1 and Strain 2) of Arctic charr. Five experimental diets with increasing inclusion of SBM or SFM were fed for 84 days to two Canadian strains of Arctic charr (initial body weight = 9 g/fish). Feeding these diets resulted in no differences in growth rate (measured as final weight or thermal-unit growth coefficient, TGC) in the two strains. Increased inclusion level of plant proteins negatively affected FE (P < 0.0001) with effects most commonly observed in groups fed SBM-based diets. The effect of the ingredient was significant (P < 0.05) on PXR gene expression in the distal intestine; PXR expression was higher with SBM than with SFM. The effect of the inclusion level of plant ingredients was significant (P < 0.05) on IL-Iβ gene expression in the spleen. Feed intake, FE, NRE, ERE, whole body crude protein, lipid, gross energy, and organo-somatic indices were significantly (P < 0.05) affected by genetic strain examined. Strain 2 exhibited higher FE and carcass crude protein content and lower carcass lipid content. The difference in FE, protein and lipid content for the 2 genetic strains of charr may indicate variations in efficiency for protein and lipid utilization, with a potential protein-sparing effect of dietary lipid noted in Strain 2.