Comparison of 13C-labeled bicarbonate and Double-Labeled Water methods for energy expenditure study in young and old adult dogs

Abstract

The energy requirement is a fundamental aspect of animal nutrition. It can be estimated by prediction equations or determined by diet history, respirometry techniques or using stable isotopes. Several factors such as age, sex, breed, body composition, physiological status, physical activity and environment can induce important variations in energy expenditure, variables that are not integrated by the prediction equations, making their estimates inaccurate. The different methods for studying energy expenditure have advantages and disadvantages, with greater or lower precision, accuracy and convenience of use. The method of diet history, although accurate in laboratory conditions, is difficult to perform in domiciliated animals, when the use of stable isotopes is advantageous. This study aims to compare the methods of double-labeled water (ADM), labeled bicarbonate (B-13C) and diet history in determining the maintenance energy expenditure of mature adult and old dogs. The study will follow a completely randomized design, with 10 mature (2.7 ± 1.19 years) and 10 old dogs (12.7 ± 2.63 years). These will be fed to maintain constant weight for 30 days, food consumption will be recorded and the metabolizable energy of the food will be determined by the total collection of feces and urine method. Their energy expenditure will be further evaluated by the B-13C and ADM method with isotopes of deuterium (2H) and oxygen 18 (18O). Bicarbonate-13C will be administered orally and 13C concentration will be measured in samples of expired air collected before the administration and 5, 10, 20, 30, 40, 60, 90, 120, 180, 360, 540 and 720 minutes after. The animals will receive 2H and 18O subcutaneously and their concentration will be measured in the plasma at baseline, after 2h (enrichment) and at 7, 10 and 14 days (decay). The volume of CO2 produced obtained by the B-13C and ADM will be compared by analysis of variance. The results of energy expenditure obtained by the three methods will be compared by analysis of variance, if differences were verified on the mean F test, means will be compared by the Tukey test. Results will also be evaluated with limits of agreements established according to Bland and Altman (1986). Values of P<0.05 will be considered significant.