Replacement of fish meal with corn gluten in diets for rainbow trout (Oncorhynchus mykiss): Effects on growth and other physiological parameters

Abstract

Background: Plant-origin meals have been proposed as an alternative to fishmeal as a source of protein in diets for rainbow trout (Oncorhynchus mykiss) and one suggested alternative is corn gluten. Goals: Determine the effects on the growth and other physiological parameters of rainbow trout juveniles fed diets made with corn gluten as substitute for fishmeal. Methods: Three diets that substituted corn gluten in ratios of 50, 75, and 100% (G50%, G75% and G100%, respectively) for fishmeal were fed during 90 days to juveniles initially weighing14.7 ± 0.2 g (mean ± standard error). We measured growth performance, oxygen consumption, P and N excretion, protein and lipid contents in muscle and liver, as well the number of lymphocytes and burst activity of the kidney macrophage. Results: Growth performance (weight gain and specific growth rate) decreased as corn gluten increased in the diet. The organisms fed with G75% and G100% diets had a significantly lower deposition of protein in the muscle with respect to the other groups, while lipid deposition increased in the same tissue. Increasing levels of the corn gluten in the diet caused increased oxygen consumption and N ammonium excretion but did not affect the number of lymphocyte and the macrophage activity. Conclusions: Corn gluten may be used at a substitution level up to 50% in diets for juvenile rainbow trout.