Energy expenditure of adult and agind dogs by food consumption, indirect calorimetry and doubly labeled water methods

• Grant number: 25/06881-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2025
• End date: November 30, 2025
• Field of knowledge: Agronomical Sciences - Veterinary Medicine
• Principal Investigator: Camila Goloni
• Grantee: Clara Uemoto Aufieri
• Host Institution: Faculdade de Medicina Veterinária (FMVA). Universidade Estadual Paulista (UNESP). Campus de Araçatuba. Araçatuba , SP, Brazil

Abstract

Determining the energy requirements of animals under different physiological conditions allows for precise nutrient intake, aligned with the animal's energy metabolism. Feed formulation must balance the concentrations of nutrients and energy in the diet to meet the known energy demands of individuals, ensuring adequate nutrient utilization without excess or deficiency under maintenance conditions. With aging, dogs experience alterations in energy requirements, and diets formulated for this life stage differ from those for young adult animals. Estimation of daily energy expenditure can be performed using different methods, which vary in practicality, cost, and accuracy. This study aims to compare three methods for estimating daily energy expenditure in adult and senior dogs: food intake-based estimation, indirect calorimetry, and the doubly labeled water (DLW) method. The experimental period lasted 60 days and included: a 30-day adaptation phase for the control of extruded commercial food intake and body weight maintenance; 20 days for indirect calorimetry using a respirometry chamber in previously adapted animals; and 10 days for the DLW method. Blood samples were collected 10 minutes before isotope administration and at 2 hours, and on days 4, 7, and 10 post-administration. Based on daily food intake (g/day) and chemical analysis of the diet, energy intake (kcal/day) will be calculated. For the indirect calorimetry method, oxygen consumption (O¿) and carbon dioxide production (CO¿) will be used to determine daily energy expenditure. For the DLW method, the difference in isotope elimination rates (²H and ¹¿O) in plasma will be used to estimate CO¿ production and, consequently, energy expenditure. The study will follow a completely randomized design, with two age groups (young adults and seniors) and three methods of estimating energy expenditure (intake, indirect calorimetry, and isotopic method), as well as the interaction between age and method. When significant effects are observed via ANOVA (F-test), means will be compared using Tukey's test. Method agreement will be assessed using Bland-Altman analysis, concordance coefficients, and linear regression. A significance level of P<0.05 will be adopted.