Assessing the bioavailability of l-lysine sulfate compared to l-lysine HCl in rainbow trout (Oncorhynchus mykiss)

Abstract A growth trial was conducted to determine relative bioavailability between two commercially available sources of supplemental lysine in rainbow trout. A basal diet, which was formulated to be deficient in lysine while meeting all other known nutritional requirements for rainbow trout was supplemented with increasing levels (0.1, 0.2, 0.4 & 0.6%) of l -lysine on an equimolar basis from one of two supplemental lysine sources; l -lysine sulfate (Bio-lys) or l -lysine HCl. Diets were fed in triplicate to groups of rainbow trout (IBW = 25 ± 0.6 g) for 12 weeks using a pair-feeding protocol. Fish which received diets containing supplemental lysine from either source exhibited improved weight gain (p   0.05) in bioavailability were observed between these two sources. Therefore, based on equimolar levels of l -lysine supplementation these two sources of supplemental lysine are equally available to rainbow trout. Statement of relevance The authors of this manuscript believe that there is a gap in the literature concerning the relative bioavailability between two prevalent sources of lysine to commercially relevant aquaculture species. Common plant protein ingredients, in particular cereal grain by-products, contain low levels of lysine. In order to formulate economical feeds, feed formulators supplement these primarily plant protein diets with supplemental sources of lysine in order to create economical diets while meeting all nutritional requirements of the animal. As the sources of lysine tested in this study, l -lysine HCl and l -lysine sulfate, are both used in the formulation of aqua feeds the relative ability of these two sources to meet the lysine requirement of rainbow trout (a major species cultured in Canada) will allow for feed formulators to use economic feed ingredients, while being confident the source of supplemental lysine they are using (either l -lysine HCl or l -lysine sulfate) will be used equally well to meet the fishes' lysine requirement.