title: Pattern of carbon dioxide production and retention is similar in adult pigs when fed hourly, but not when fed a single meal.
abstract: BACKGROUND
  The understanding of bicarbonate kinetics and CO2 retention in the body is necessary to conduct amino acid tracer oxidation studies in both humans and laboratory animals. Significant metabolic activity is associated with eating which can affect bicarbonate steady state kinetics. A study was conducted to assess the impact of feeding regimen on the recovery of labelled bicarbonate and energy expenditure in adult female pigs (sows). Five catheterized sows (235 +/- 5 kg) were fed semi-synthetic diets as: a single meal 2 h into the infusion after an overnight fast, or in eight hourly meals starting 2 h before the infusion. Oxygen consumption, CO2 production and 14CO2 recovery (ie fraction not retained) were determined during primed, constant intravenous infusions of NaH14CO3.
  
  
  RESULTS
  The 14CO2 recovery (%) after fasting (58.1 +/- 4.8) was lower than that after single meal feeding (78.8 +/- 5.9) or hourly meal feeding (81.0 +/- 2.6, P = 0.03). CO2 production correlated with 14CO2 recovery during hourly feeding (r = 0.40, P = 0.01); this relationship was not significant after single meal feeding (P = 0.30), probably due to physical activity-associated CO2 production.
  
  
  CONCLUSIONS
  The correlation of CO2 retention factors with CO2 production during hourly feeding suggests that this regimen should be preferred for future amino acid kinetics studies.
authors.affiliation: Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, T6G 2P5 Canada. smoehn@ualberta.ca
authors.forename: Soenke
authors.initials: S
authors.lastname: Moehn
authors.forename: Robert F P
authors.initials: RF
authors.lastname: Bertolo
authors.forename: Paul B
authors.initials: PB
authors.lastname: Pencharz
authors.forename: Ronald O
authors.initials: RO
authors.lastname: Ball
mesh_terms: D000596:Amino Acids / Q000493:pharmacokinetics*; D000821:Animal Feed; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D002153:Calorimetry, Indirect / Q000295:instrumentation; D002245:Carbon Dioxide / Q000378:metabolism*; D002250:Carbon Radioisotopes / Q000032:analysis; D018592:Cross-Over Studies; D004044:Dietary Proteins / Q000493:pharmacokinetics*; D004734:Energy Metabolism; D005215:Fasting / Q000378:metabolism; D005248:Feeding Methods; D005260:Female; D007408:Intestinal Absorption; D007700:Kinetics; D010101:Oxygen Consumption; D019518:Postprandial Period; D011897:Random Allocation; D034421:Sus scrofa / Q000502:physiology*; D013997:Time Factors
chemical_list: D000596:Amino Acids; D001639:Bicarbonates; D002250:Carbon Radioisotopes; D004044:Dietary Proteins; D002245:Carbon Dioxide