Good morning, good afternoon, and good evening, everyone. 
My name is Su A Lee. 
Today, we’ll be discussing Effects of high fiber on gas production and net energy in diets fed to group-housed pigs.
This work was presented in 2024 EAAP annual meeting.
Energy is the most expensive component when formulating diets for pigs.
Therefore, it is important to determine concentrations of energy in feed ingredients to reduce feed costs by maximizing the growth performance of pigs. 
Equipment to determine net energy values of feed ingredients is available only at a few universities in the world – but the University of Illinois recently constructed such a facility. 
This facility has a capacity to hold the multiple number of pigs depending on the size of pigs and is installed with indirect calorimeter chambers that are airtight, which enables us to measure the gas consumptions and productions of pigs.
The demand for calculating carbon footprint is increasing so everyone would ask what the values are in the future.
To cut down on the cost of pork production, high-fiber ingredients are often used for formulating pig diets. However, an increase in the amount of dietary fiber in pig diets may have a negative impact on the digestibility of nutrients and energy. Carbon footprint from pork production is related to emissions of greenhouse gases including carbon dioxide, nitrous oxide, and methane from pigs. Emission of gases may be correlated with the composition of feeds, and it is thus possible that feeding pigs with diets containing high-fibrous feed ingredients affects the gas exchange, which also impacts concentration of net energy in diets. 
Therefore, the objective of this experiment was to test the null hypothesis that feeding pigs with a high-fiber diet does not affect the apparent total tract digestibility of energy and nitrogen, retention of nitrogen, and net energy as well as gas consumption and production by pigs.
For this experiment two diets were used. The first diet was formulated based on corn and soybean meal with normal fiber contents. The second diet contained corn and soybean meal and also contained 35% wheat middlings to have a diet with an elevated level of fiber. In this presentation, the normal-fiber diet will be referred to as the low-fiber diet. 
We utilized 24 pigs with an initial body weight of approximately 41 kg.
Because there were 6 indirect calorimeter chambers, 4 pigs were housed in each chamber.
The 6 chambers were allotted to 2 dietary treatment using a triplicated 2 by 2 Latin square design with 2 periods to have a total of 6 replicate chambers per treatment. 
Feces and urine samples were collected for 6 days after 7 d of adaptation using the time-to-time procedure.
Consumption of oxygen and productions of carbon dioxide and methane were also measured to determine the total heat production.
Urine samples were collected during the fasting period and fasting heat production was also determined.
Dried fecal samples were analyzed for dry mater, gross energy, and nitrogen 
and urine samples were analyzed for gross energy and nitrogen.
The apparent total tract digestibility and concentrations of digestible, metabolizable, and net energy were calculated and retention of N was also calculated. 
Total heat production and fasting heat production were calculated using an equation suggested by Brouwer, 1965 and we used the analyzed gas data and N in urine for calculating them.
Net energy was calculated by subtracting energy in feces and urine and total heat production and then by adding the fasting heat production.
The statistical model included diet as the fixed variable and period and chamber as random variables.
Moving on to the results, let me set up the slides first.
The blue bars represent data for the low-fiber diet and orange bars represent data for the high-fiber diet. 
Results indicated that the apparent total tract digestibility of dry matter and gross energy was greater in the low-fiber diet compared with the high-fiber diet.
Basically the same was observed that the apparent total tract digestibility of nitrogen and retention of nitrogen in percentage intake were greater in the low-fiber diet compared with the high-fiber diet.
Looking at the net energy, the net energy in the low-fiber diet was greater than in the high-fiber diet. 
The energy and nitrogen data were concepts we had learned from previous experiments for a long time, so they were not new to us.
Now let’s look at the gas data.
All gas data will be presented per one pig by simply dividing data by the number of pigs in one chamber.
This slide shows gas consumption and productions.
The consumption of oxygen and production of carbon dioxide were greater by pigs fed the low-fiber diet compared with the high-fiber diet. 
It may seem that I did not include data for methane, but in reality, the methane production is very low compared with the scales of oxygen and carbon dioxide. 
Therefore, I have prepared a separate slide for methane production.
Even though the bars appear to show a difference, the statistical analysis demonstrated that there was no difference in methane production between pigs fed the two diets. 
The greater amount of gas exchanges can be explained by greater energy content in the low-fiber diets, as indicated by the greater average daily gain and average daily feed intake of pigs fed the low-fiber diet compared with pigs fed the high-fiber diet. 
Because the gas data presented in the previous slides did not account for feed intake, the oxygen consumption and gas productions were adjusted based on the feed intake of pigs to ensure a fair comparison between diets with different feed intakes.
When adjusted with feed intake, oxygen consumption and methane production were greater in pigs fed the high-fiber diet than in pigs fed the normal-fiber diet, but there was no difference in carbon dioxide production. 
The higher oxygen consumption and methane production in pigs fed the high-fiber diet could be explained by the increased metabolic effort required to digest and ferment fiber. High-fiber diets increase microbial fermentation in the hindgut, which also increases methane production as a byproduct. Additionally, fiber digestion requires more energy and prolonged digestive activity and thus increases oxygen consumption. We expected the carbon dioxide production to be greater in pigs fed the high-fiber diet because of the higher fiber content; however, this was not observed in this experiment. 
To reflect metabolic efficiency, the gas data were also adjusted with weight gain of pigs. 
The results indicated that no differences in oxygen consumption and carbon dioxide production between the two diets. However, methane production was greater in pigs fed the high-fiber diet. 
In conclusion, feeding pigs with the wheat middlings diet reduced digestibility of energy, retention of nitrogen, and concentration of net energy in diet compared with feeding a corn-SBM diet. 
Because of the increased feed intake, O2 consumption and CO2 production were greater in pigs fed the low-fiber diet than in pigs fed the high-fiber diet
However, if gases were corrected for daily feed intake, O2 consumption and methane production were greater in the high-fiber diet and methane production was greater in the high-fiber diet when we take account of weight gain of pigs.
Thank you for listening to my presentation and I would like to acknowledge everyone from Dr. Stein’s lab. 
If you want to learn more about our research that we are conducting in the Stein Monogastric Nutrition Laboratory, please visit our website. Thank you.