How much does it cost? Teaching physiology of energy metabolism in mice using an indirect calorimetry system in a practical course for veterinary students

Abstract

In endothermic mammals total energy expenditure (EE) is composed of basal metabolic rate (BMR), energy spent for muscle activity,thermoregulation, any kind of production (such as milk, meat, or egg production), and the thermic effect of feeding. TheBMR is predominantly determined by body mass and the surface-to-volume ratio of the body. The EE can be quantified by eitherdirect or indirect calorimetry. Direct calorimetry measures the rate of heat loss from the body, whereas indirect calorimetry measuresoxygen consumption and carbon dioxide production and calculates heat production from oxidative nutrient combustion. Adeep and sustainable understanding of EE in animals is crucial for veterinarians to properly calculate and evaluate feed rationsduring special circumstances such as anesthesia or in situations with increased energy demands as commonly seen in highyieldinglivestock. The practical class described in this article provides an experimental approach to understanding how EE canbe measured and calculated by indirect calorimetry. Two important factors that affect the EE of animals (the thermic effect offeeding and the effect of ambient temperature) are measured. A profound knowledge about the energy requirements of animallife and its measurement is also relevant for education in general biology, animal and human physiology, and nutrition.Therefore, this teaching unit can equally well be implemented in other areas of life sciences