Interview with Dr. Walter Gerrits: Calorimetry Systems

Dr. Edgar Oviedo collaborator and co corresponding author for nutriNews International had the opportunity to speak with Dr. Walter Gerritts Professor of Animal Nutrition at Wageningen University about calorimetry systems and their applications in animal nutrition.  His research focuses on digestive physiology and macronutrient metabolism in various species, mostly pigs and calves. Professor Gerrits has focused on interactions between animal nutrition, health and welfare. This interview took place during the 7^th EAAP International Symposium on Energy and Protein Metabolism and Nutrition (ISEP 2022) held in Granada (Spain) from September 12-15, 2022. Dr. Edgar Oviedo: We are here at ISEP 2022 with Dr. Walter Gerrits. Dr. Gerritts you will be conducting a colorimetry course in this event, after the main program has finished. Could you tell us what you will be discussing in this course, and what are the main applications for these calorimetry systems? Dr. Walter Gerrits: Thank you Dr. Oviedo. Indirect calorimetry is  a way to measure heat production by the measurement of oxygen consumption and the production of carbon dioxide (CO2). It is one of the standardized methods that is used by lots of people attending this conference to measure the energy balance of animals. It has been used quite a lot to measure the energy values of feed ingredients, but increasingly people have started to use these types of techniques to measure environmental conditions, interactions between the immune system and nutrition. So, it is a technique that you can use to quantify the production of heat, but at the same time people use it to measure nitrogen (N) balance which allows you to get an estimate of protein deposition and fat deposition. It can be used for a wide range of animals. However, this kind of technique requires a certain degree of expertise in order to be conducted. That is why we started dictating this course every three years since 2013, in conjunction with ISEP and Davis. It is mainly intended for technicians and PhD students, although it is also available for other people that want to implement these types of techniques within their research. Dr. Oviedo: With indirect calorimetry you can also probably measure the impacts of animal activity, whether they are moving or staying still. How can you quantify locomotion through these systems, is it possible to include this within a model that calculates maintenance requirements? Dr. Gerrits: Well that is a lot of questions in one, but yes you can measure locomotion, and quantify it. Therefore, you can separate the heat production that is related to physical activity from what is unrelated to this type of activity. The problem with this is that most respiration chambers are too small for animals to be moving around freely, but there are facilities available where you can have group housed pigs or poultry, and even free ranging cows. If you for example have a surface of 6x3m, you could have 2 to 3 cows in there but that is the maximum space that you have available. If you want to measure heat production during grazing conditions or out in the field for example, you need to have estimates that are calibrated in this kind of calorimeters. So you can do that too, but measurements in respiration chambers are with limited movement. Read full interview here