Hi, everyone. My name is Su A Lee from the Stein Monogastric Nutrition Laboratory at the University of Illinois. 
I will be discussing the effects of pelleting and reducing particle size of corn on net energy in diets fed to pigs that were group-housed. 
This work was presented in 2023 ASAS Midwest Meeting.
Pelleting is a process of compacting and shaping feed ingredients into small pellets or granules.
This thus helps in the ease of handling, transport, storage, and consumption of animals.
Pelleting can potentially increase the digestibility of nutrients in pigs as well. 
The pelleting process involves heat and pressure, which can improve the digestibility of starch and amino acids in feed ingredients by breaking down protein structures, reducing anti-nutritional factors, and gelatinizing starch.
Because pelleting also increases palatability of pigs and digestibility of nutrients, the growth performance of pigs is improved as well. 
However, because the process, again, involves heat and pressure, this may induce the heat damage of amino acids. Lastly, the diets cost more because this is an extra process.
Reducing particle sizes of grains increases the surface area available for enzymatic activity, and thus leads to increased digestibility of nutrients and also growth performance of pigs.
However, because finely ground diets can generate dust and have negative impact on gut health, reducing particle size can cause health problem. Like pelleting, reducing particle size increases the overall cost of feed production because this requires additional grinding or processing steps.
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 maximize the growth performance of pigs. 
Equipment to determine net energy values of feed ingredients is available only at few universities in the world – but the University of Illinois recently constructed such a facility. 
This facility is installed with indirect calorimeter chambers that are airtight and have a capacity to hold the multiple numbers of pigs depending on size of pigs. 
It is possible that net energy in diets fed to group-housed pigs is different from what has been determined in individually housed pigs. 
Energy is the most expensive component when formulating diets for pigs.
Therefore, this experiment was conducted to test the hypothesis that particle size reduction and pelleting, separately or in combination, increase N balance, apparent total tract digestibility, ATTD, of fiber and fat, and concentration of net energy in corn-soybean meal diets fed to group-housed pigs
In this experiment, diets were arranged with 2 by 3 factorial and all diets contained corn and soybean meal.
the first factor was the diet form, meal or pelleted
And the second factor was particle size of corn. One batch of yellow dent corn was prepared and ground into 3 different particle sizes from 700, 500, to 300 microns.
Pigs were fed ad libitum and had free access to water throughout the experiment. 
Because multiple number of pigs were hounded in one chamber, pigs shared one feeder and water nipple.
we utilized 24 pigs with an initial body weight of approximately 30 kg.
There were 6 indirect calorimeter chambers and thus 4 pigs were housed in each chamber.
The 6 chambers were allotted to a 6 x 6 Latin Square design using 6 trts and 6 periods to have a total of 6 reps per diet.
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, nitrogen, acid hydrolyzed ether extract, and total dietary fiber and urine samples were analyzed for gross energy and nitrogen.
The ATTD of nutrients 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, 1985  and we used 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.
Contrast coefficients were used to compare the two diet forms, linear effects of reducing particle size, and the interaction between diet form and particle size.
Moving on to the results, let me set up the slides first.
All data are presented per one pig by simply dividing data by the number of pigs in one chamber.
The yellow represents diets in meal form and orange represents diets in pelleted form. 
Within each diet form, there are 3 different particle sizes of corn that are 700 all the way down to 300 microns.
The weight of orts from pigs fed meal diets was linearly increased by reducing particle sizes of corn, but this was not observed in pelleted diets. 
Regardless of particle size of corn, the weight of orts was greater in meal form than in pelleted form.
In a couple of slides, we will look at nitrogen balance.
The ATTD of N was linearly increased by reducing particle size of corn in meal diets, but the effect was less in pelleted diets. 
The ATTD of N was greater in pelleted diets compared with meal diets.
There were no interactions between diet form and particle size of corn and the effects of pelleting or reducing particle size were not observed for retention of N that is % of intake.
The average digestibility of total dietary fiber was about 63% in diets.
Like the nitrogen retention, there were no interactions between diet form and particle size of corn and no main effects were found.
We are looking at the ATTD of acid hydrolyzed ether extract in diets.
The ATTD of fat was linearly increased by reducing particle size of corn in meal diets, but the effect was less in pelleted diets. 
The ATTD of fat was greater in pelleted diets compared with meal diets.
For the ATTD of energy, 
The ATTD of energy was linearly increased by reducing particle size of corn in meal diets, but the effect was subtle in pelleted diets 
The ATTD of energy was greater in pelleted diets than in meal diets. 
Basically the same thing was observed for digestible energy and metabolizable energy that the particle size effects were grater in meal diets than in pelleted diets.
Concentration of metabolizable energy was greater in pelleted diets than in meal diets. 
The increases in the ATTD of energy and concentrations of energy by pelleting is explained by the fact that the heat generated during pelleting helps in gelatinizing starch, which is one of the energy source in feed ingredients, and thus making them more digestible for pigs. 
For net energy, there was a linear increase when particle size was reduced from 700 to 300 microns in both diet forms, but the effect was greater in meal form than in pelleted form.
Regardless of particle size, pelleting increased the concentration of net energy in diets fed to group-housed pigs.
Interactions were found in this experiment indicating that the effects of reducing particle size were grater in meal diets than in pelleted diets. 
This is because pelleting also reduces particle size of grains and thus the effects of reducing particle size in pelleted diets may not be as efficient as it was in meal diets.
Regardless of particle size, pelleting increased nutrient digestibility and energy concentrations in diets fed to group-housed pigs and similar was observed when the particle size of corn was reduced. 
I would like to acknowledge everyone from Dr. Stein’s lab. And if you want to learn about the research we are conducting in the Stein Monogastric Nutrition Laboratory, please visit our website at nutrition.ansci.illinois.edu, or search “Stein” and “pig” on google. Thank you for listening.