It is necessary to apply more sensitive techniques to improve our limited understanding of amino acid (AA) requirements of adult cats. The non-invasive indicator amino acid oxidation (IAAO) technique is highly sensitive in mature animals. However, while it has been widely applied in different species, this technique has yet to be used in cats. We used six healthy adult cats to evaluate whether the IAAO method could be successfully applied in this species. A similar continuous small meals regimen as reported in IAAO studies in dogs was used. An oral primed-constant isotope infusion protocol was applied where L-13C-Phenylalanine (L-[1-13C]-Phe) was used as the tracer and the oxidation of L-[1-13C]-Phe as the response of interest. Breath samples were collected to determine enrichment of 13CO₂ in breath and calculate oxidation of L-[1-13C]-Phe. While we were able to collect breath samples using calorimetry chambers and capture enrichment of 13CO₂ in breath, cats did not achieve steady state, which is necessary to calculate oxidation of L-[1-13C]-Phe. Modifications in the isotope protocol should be made to achieve steady state of 13CO₂ in breath, and thus, to successfully apply the IAAO technique to determine requirement of AA in adult cats.

Read the full article in the Journal of Animal Science.