A  digestibility study  conducted by  São Paulo State University  scientists determined the nutritional value of various ingredients for dog foods. Eight adult dogs were housed in metabolic cages, and distributed into 8 × 8 Latin square experimental design, with eight diets and eight replicates per diet. The difference, or substitution method was used to estimate ingredient digestibility. A reference diet was formulated based on nutritional requirements of dogs. For each test diet, 300 g/kg of the reference diet was replaced with the ingredient evaluated. All the diets were extruded.

Total tract apparent nutrient digestibility

Chart courtesy of  All About Feed