A study of the discrete and interactive effects of different polysaccharides on the digestibility of diets fed to barramundi (Lates calcarifer)

This study examined the single, paired and combined inclusion effect of a range of different polysaccharide types on the dry matter, protein and energy digestibility of diets fed to barramundi (Lates calcarifer). The different polysaccharides included pregelled starch, cellulose, lignin and pectin. 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. Pectin had the largest effect on drymatter, while lignin had the greatest impact on diet protein and energy digestion. In the diets with paired combinations of polysaccharides, lignin and pectin were responsible for negatively synergistic interactions in all digestibility parameters. These results show that different polysaccharide classes can have distinctly different effects on diet digestibility parameters.