A comparison of the digestibility of diets and ingredients fed to rainbow trout (Oncorhynchus mykiss) or barramundi (Lates calcarifer) - the potential for inference of digestibility values among species

This study aimed to determine if the diet and ingredient digestibilities from one carnivorous species of fish could be applied to another carnivorous species of fish. To do this, the digestibility of a series of diets and grain and poultry waste ingredients were compared when fed to either rainbow trout or barramundi. The same batches of diets were fed to either species prior to faecal collection using stripping techniques. There were strong correlations between the digestibilities of the diets and ingredients between the two species for each of the dry matter, protein and energy digestibility parameters. Both diet and ingredient digestibility values were similar for both species, although protein and dry matter digestibilities were generally higher for trout. The correlations were generally stronger for diet digestibilities than the ingredient digestibilities with the diet energy digestibility the strongest of the correlations (R2 =0.925, P = 0.0001). Ingredient digestibilities were weakest for the protein digestibility (R2 = 0.552, P = 0.0218), and this relationship is heavily dependent on one or two outlier values. The strong correlation between both diet and ingredient digestibilities between the two fish species indicates that there is considerable potential for the application of digestibility data for one carnivorous species to another.