Influence of a flooding dose of valine on key indicators of metabolic status in the growing pig

Summary A key concern with the flooding dose technique for measuring protein synthesis is that a large dose of amino acid (AA) can potentially change the animals’ hormonal and nutritional status, which in turn can influence protein synthesis. Among stable isotope tracers, 1‐[ 13 C]‐valine is the preferred AA for measuring protein synthesis in gut tissue and mucins. A study was conducted to determine the impact of a flooding dose of valine on the metabolic status of pigs. Six barrows [16.5 kg body weight (BW)] were randomly assigned to intravenous infusions of either 150 m m valine (1.5 mmol/kg BW) or physiological saline, following a crossover design. Blood samples were taken 10 min prior to infusion, at the end of infusion, at 10‐min intervals for 60 min post‐infusion, and at 90 and 120 min post‐infusion. Plasma concentrations of insulin, glucose, AA, urea nitrogen and packed cell volume (PCV) were measured. Infusion of valine increased plasma valine concentrations (4129 vs. 582  μ m ; P  <   0.05) but had no influence on PCV (26.4% vs. 27.2%) and plasma concentrations of glucose (6.0 vs. 5.8 m m ) and insulin (8.2 vs. 8.5  μ U/ml; P  >   0.10). Plasma urea nitrogen concentration was reduced with valine infusion (8.5 vs. 7.8 mg/dl; P  <   0.05). A flooding dose of valine had no impact on plasma concentrations of AA, and specifically branched‐chain AA such as leucine (240 vs. 231  μ m ) and isoleucine (310 vs. 331  μ m ; P  >   0.10). There was, however, a slight increase in the plasma concentrations of threonine (224 vs. 263  μ m ; P  <   0.05) and a tendency towards reduced glycine (1387 vs. 1313  μ m ; P  <   0.10). The results indicate that a flooding dose of valine does not cause a substantial change in the metabolic status of growing pigs and is therefore suitable for measuring protein synthesis rates.