Metabolic availability (MA) of an amino acid (AA) is the fraction of a dietary AA that is digestible and available for protein synthesis. Chicken meal (ChM) and peas are commonly used protein sources in extruded dog foods, with peas containing more fiber. Moreover, the essential AA methionine (Met) is first limiting in peas. Typical MA studies use a 2-d diet adaptation, but high dietary fiber may impact MA, requiring longer adaptation periods. The objective of this study was to determine the MA of Met in peas and ChM compared to a semi-synthetic crystalline AA reference diet (BAS) limiting in Met and assumed to be 100% MA, using the indicator amino acid oxidation (IAAO) technique after 2 (D2) and 6 (D6) d diet adaptation. As protein synthesis is inversely proportional to oxidation, the reference protein is expected to have a lower oxidation response than the ingredient of interest. Overall, the BAS diet had no oxidation response, suggesting a different limiting AA. ChM had the lowest oxidation response, and the MA of peas was 66% and 51% of ChM on D2 and D6, respectively. Length of adaptation had no effect on MA of Met, indicating the standard 2-d diet adaptation is sufficient.

Read the full article in the Journal of Animal Science.