The influence of various starch and non-starch polysaccharides on the digestibility of diets fed to rainbow trout (Oncorhynchus mykiss)

Abstract This study examined the effect of increasing inclusion levels of various polysaccharides on the dry matter, protein and energy digestibility of diets fed to rainbow trout ( Oncorhynchus mykiss ). The different polysaccharides included pregelatinised starch, cellulose, lignosulphonate, pectin and mannan. There were significant differences among the digestibility parameters of the diets with the different inclusion levels of each of the different polysaccharide types. Using a MANOVA analysis effects were noted for polysaccharide type, inclusion level and interaction terms on the digestibilities of dry matter, protein and energy. Cellulose addition resulted in a reduction in both dry matter and energy that was largely commensurate with its inclusion level, but its effect on protein digestibility was marginal. Starch had the least effect on any of the digestibility parameters of all the polysaccharide types examined. At low inclusion levels lignosulphonate was observed to have the greatest impact on all digestibility parameters, particularly on protein digestibility. These results show that different polysaccharide classes can have distinctly different effects on diet digestibility parameters. The results also show that some classes of polysaccharide have greater effects than others.