Dog owners pay lot of attention on providing proper nutrition to their dog that will support longevity and good health. Great effort is therefore made by feed producers concerning information about nutritional quality of dog food ingredients and at to what extent they cover the nutritional requirement of dogs at different life stages. Protein and amino acid content and utilization is of great importance in the evaluation of pet food ingredients. A key factor in protein utilization is digestibility. In dogs digestion and absorption in the small intestine will be the main site for evaluating digestibility since 90 % of digestion take place in this part of the digestive tract. Ileal digestibility values will therefore be more correct than apparent total tract digestibility values that are influenced by degradation of protein in the colon. Degraded and metabolized protein from fermentation processes in the colon is not absorbed and utilized as amino acids in the small intestine. Microbial degradation produces volatile N compounds that will not be accounted for and therefore total tract digestibility values will overestimate protein digestibility.