Calibration and validation of a carbon oxidation system and determination of the bicarbonate retention factor and the dietary phenylalanine requirement, in the presence of excess tyrosine, of adult, female, mixed-breed dogs

摘要: Carbon oxidation methods have been used as rapid and sensitive to determine whole-body AA requirements in multiple species. The objectives of the current studies were validate complete CO recovery, bicarbonate retention factor, estimate Phe requirement, presence excess Tyr, adult dogs using direct technique. In this series studies, 2 chambers constructed calibrated ensure accurate collection breath CO. First, 104.6 ± 7.1% was recovered from suggests that appropriately designed for efficient recovery. Second, we determined 5 repeated oral dosing a tracer (NaHCO) with small meals. At isotopic physiological steady state, 102.5 2.6% delivered NaHCO breath. Third, when Tyr supplied excess, by rate appearance (CO). Dogs ( = 5) fed test diets different concentrations ranging deficient excessive d prior conducting studies. mean requirement (when excess) 0.535% diet (upper 95% confidence interval 0.645% diet) on an as-fed basis or 0.575% 0.694% DM based calculated (modified Atwater calculation) dietary ME density 3.73 Mcal/kg DM. These data support use carbon isotope measure indispensable suggest recommendations may be low.