Hello, everyone. My name is Cristhiam Munoz, and today I'm going to give you an update about the calorimetric unit for group-housed pigs. I want to start giving you the energy partitioning, which starts with the gross energy value, which is the total amount of energy that is contained in the feed. But if we subtract the energy that is present in the feces, we can actually calculate the digestible energy value. If we also calculate the energy that is lost in the urine, we can calculate the metabolizable energy value. These two values have been the most commonly used in the U.S. for diet formulations. However, if we can also calculate the amount of energy that is being lost in the form of heat, we can calculate the net energy value, which is believed to be more accurate than the other two values because we account for the total amount of energy losses in the system. This total amount of energy, or total heat production or fasting heat production, could be calculated using the oxygen consumption and CO2 and methane production of the animals. These two forms of heat can be determined using indirect calorimetry. The only difference between total heat production and fasting heat production is that total heat production is calculated in the fed state, whereas the fasting heat production is calculated during the fasting period. Then, those values of oxygen and CO2 and methane are corrected by urinary nitrogen. And at the end, those values are subtracted from the metabolizable energy value to obtain net energy. Therefore, the swine calorimetric unit was designed to calculate total heat production and fasting heat production to determine net energy. The objective of the swine calorimetric unit is to determine net energy in complete diets and feed ingredients used in commercial farms and using also commercial conditions such as group housing allocation and ad libitum access to feed. In the 3D plan of the SCU, we can see the distribution of the unit. We have eight feed storage rooms where the feed is kept under controlled conditions to avoid feed spoilage. We have six calorimetric chambers where the animals will be placed for measurement, and we have three equipment rooms where the equipment to control two chambers at a time are placed. There is also a computer room where all the equipment in the unit is controlled, and there is also an alarm system which monitors all the equipment in the unit at all times. There is also a mechanical room where the utility entrance is located. In this plan also, we can find a door in the west side which is used for animal and personnel entrance, which gives us access to the corridor which connects the rooms inside of the unit. This is an overview of the complex between the equipment room and one of the chambers. In the chamber, we can find two main sections: one for animal allocation and the secondary section for collection of feces and urine to calculate digestible energy and metabolizable energy. In the equipment room, we can find three main systems: the first one is the fresh air supply system, the second one is the temperature and humidity control system, and the third one is the gas analyzer system. If we take a look at the chamber features, we can see in the picture to the left that both the main and the secondary sections are airtight by the use of a seal in the frame of the two doors. The main section is equipped with a feeder and drinker similar to the ones used in commercial conditions. The capacity of the main section is up to ten pigs, depending on the size. And we can also find the air diffuser in the ceiling, which is responsible for the mixing of the air inside of the chamber and where the fresh air is being supplied. In the secondary section, we can find two columns composed by two rows of feces screens and one row of urine pans. This design has the purpose of assuring the collection of the total amount of feces when the upper feces screen is out for collection. Therefore, the lower feces screen can capture the feces that could be excreted in that moment. Each urine pan has the capacity of 100 liters to assure also the total collection of urine. In the equipment room, the first system that can be described is this fresh air supply system. We need to control the amount of air that is being supplied to the chamber with a high precision because we need to avoid animal suffocation but also avoid the dilution of the gases inside of the chamber. This system is composed for one centrifugal inlet fan which brings the air from the equipment room to the chamber, and the air stream is controlled by the electronic valve called Accuvalve. Each of the chambers is set with a slight positive pressure because we need to avoid external air to get inside of the chamber without being controlled. And this positive pressure is achieved by the use of a rotatory valve in the exhaust pipe. And this positive pressure could be monitored using a wall manometer that is placed next to the system. The second equipment that could be described is the temperature and humidity control system. This system controls these two environmental conditions with a high accuracy because it’s needed to avoid the animals using energy for thermal regulation. This equipment could be controlled locally by the use of this pad or also remotely using the master computer in the computer room. This system is important because in the future we will simulate different environmental conditions that can be found also in commercial farms, such as high or low relative humidity and temperature, and see what will be the impact on net energy. The system operates using the dewpoint control, which controls the temperature of the air and also the temperature of the water that is being sprayed to control humidity. The last system is the gas analyzer system. This system measures the concentration of oxygen, CO2, and methane inside and outside of the chamber. This system is composed for one multiplexer which selects one out of three sources of air to be analyzed. It also contains a sub sampler and three gas analyzers: one for carbon dioxide, one for methane, and one for oxygen. To explain this system in a greater detail, I brought this chart as an example of the equipment room number one and chambers one and two. The multiplexer received a sample of air from one of the chambers and also for the fresh air supply, which is going to be the baseline. This multiplexer selects one of the sources at a time and sends the air stream to the sub sampler. This sub sampler takes 250 milliliters of air to be sent to the analyzers for analysis of CO2, CH4, and O2. In a period of 24 hours, the first hour is used for feeding and sample collection, and the second hour is used for stabilization of the conditions. The other 22 hours will be the period for collection. And if we take for example hour 12, we can see that we measure 10 minutes per line, and this process is repeated within the hour. So at the end, we will have two sets of 10 minutes per line per hour and we average this value per gas per line per hour. And at the end we sum the values of the three gases in the 22 hours, and we are able to estimate the variation of these gases in a 24-hour period. The calculations needed to calculate total heat production includes the transformation into standard temperature, pressure, and dry units for the inlet air flow to take into account variations of temperature, atmospheric pressure, and also humidity. Then, a correction factor needs to be applied to determine the gas volume in the chambers, and those values are then used to determine total heat production. Two experiments have been designed to test the swine calorimetric unit. The first one has the hypothesis that there are no differences among chambers. And for this experiment, a common diet has been designed. A corn-soybean meal diet will be used for this experiment, which is the most commonly used in commercial conditions. We will place five pigs per chamber with an average body weight of 38 kilograms and the experiment would last 14 days for a single period. In this experiment, we will measure digestible energy, metabolizable energy, total heat production, and net energy. During these 14 days, the first five days are considered the adaptation period. And the following six days, feces, urine, and gas exchange will be collected and measured to calculate total heat production. Then a fasting period of 36 hours, where the first 24 hours the animals will consume the remaining feed in the intestinal tract, but in the last 12 hours it is believed that the animals use the endogenous reserves of energy. And during this time, gas exchange and urine will be collected and measured to calculate fasting heat production. And the morning of day 14, the animals will return to the SRC facilities. The second experiment has the hypothesis that there are differences in total heat production between low protein and high protein diets. It is believed that the animals that are fed with a high concentration of protein will spend more energy in metabolism of the excess amino acids, and therefore the net energy will be lower. For this experiment, two diets containing 21% and 14% of crude protein will be formulated. For the diet containing 14% of crude protein, the diet will be supplemented with crystalline amino acids to meet the requirements of all indispensable amino acids. We will use five pigs of an average of body weight of 50 kilograms per chamber. And this experiment will have two periods of 14 days each. We will calculate digestible energy, metabolizable energy, total heat production, and net energy. And each of the periods will have the same distribution that I explained before. For future research, the swine calorimetric unit will compare the net energy values obtained for individual and group-housed allocation, and we will focus on the determination of net energy in feed ingredients and diets fed to pigs in commercial conditions. I want to thank you all for your kind attention. And if you want to learn more about this topic or other topics, please visit our website, which is nutrition.ansci.illinois.edu.