My name is Jessica Acosta. I am a Ph.D. student in the monogastric nutrition laboratory of Dr. Hans Stein at the University of Illinois and today I will share with you the results of one of my experiments where we observed that xylanase or a stimbiotic increased growth performance and total tract digestibility of nutrients by pigs weaned from sows fed a lactation diet without or with xylanase. This work was presented at the 38 Spanish feed industry FEDNA congress, on December 13, 2023.   
Arabinoxylans are the main type of polysaccharide found in the fiber portion of cereal grains and cereal grains coproducts. For example, in corn and wheat, arabinoxylans are reported as 58 and 64% of the dietary fiber content, whereas other dietary fiber contents, such as cellulose or Beta glucans, are present in less concentration. In co-products such as Distillers dried grains with solubles and wheat bran, obtained after processing of the cereals grains, the concentration of total dietary fiber increases to 25 and 35 percent, respectively, but still, the arabinoxylans represent most of the fiber portion. 
But, what are arabinoxylans? Arabinoxylans are a polysaccharide made up of a chain of xylose units with sidechains of arabinose, galactose, acetyl groups, or phenolic acids that make this molecule a complex carbohydrate that may interact with lignin and other polysaccharides. Increased amounts of arabinoxylans from cereal grains and co-products in diets for pigs have been associated with negative effects, such as reduced digestibility of nutrients, less energy available for the animals, and, therefore, less growth performance. Pigs lack fiber-digesting enzymes; they rely on microbial fermentation when consuming great amounts of dietary fiber. However, arabinoxylans are not fully fermented and therefore do not contribute too much to the energy requirement of the animals.
Therefore, exogenous enzymes such as xylanase, have been proposed to improve the fermentability of dietary fiber. Xylanase is a carbohydrase that breaks down the xylose chain of the arabinoxylan. This results in the release of Xylose units, and Xylo-oligosaccharides. Xylo-oligosaccharides are sugar oligomers that are composed of 2 to 10 monomeric units, that can be easily fermented by the microorganisms in the hindgut.
A stimbiotic, known as a promoter of fiber fermentation, combines the xylanase activity with the xylo-oligosaccharides, which may result in changes in the intestinal microbiome to favor fiber fermentation, but it is not known if the effect of stimbiotic is similar to that of xylanase. There is also a lack of data on how dietary xylanase fed to lactating sows potentially may impact growth performance or digestibility of nutrients by pigs weaned from sows fed xylanase.
Therefore, we conducted an experiment to test the hypothesis that xylanase or a stimbiotic improves growth performance and the apparent total tract digestibility of dry matter, gross energy, and total dietary fiber, and the concentration of digestible energy of diets for weanling pigs. The second hypothesis was that the effect of using xylanase in post-weaning diets is greater in offspring of sows fed xylanase in lactation than in offspring of sows that were fed a diet without xylanase during lactation.
Moving on to the materials and methods. A control diet containing corn, soybean meal, and wheat middlings, and two additional diets with the addition of 100 g / ton of xylanase or stimbiotic were formulated. Diets contained sixteen thousand units of xylanase. Diets included 0.4% of titanium dioxide as an indigestible marker and nine experimental diets were used, three in each phase.
A 3-phase feeding program was used. Day 1 to 14 was phase 1, day 15 to 28 was phase 2, and day 29 to 42 was phase 3. Animals were in the experiment immediately after weaning. Pigs were weighed at the beginning of the experiment and at the end of each phase. Also, the amount of feed left in the feeders was weighted at the end of each phase. From d 26 to d 28 and day 40 to d 42, fecal samples were collected from all pigs in each pen via anal stimulation. 
120 pigs from sows fed a control diet during lactation and 120 pigs from sows fed a diet with xylanase during lactation were used. Animals were allotted to 4 blocks, in a 2 by 3 factorial design, with 8 replicates per treatment. There were 5 pigs per pen and 6 treatments. 
Data were analyzed using PROC mixed of SAS with the pen as the experimental unit, diet, sow group and the interaction between diet and sow group as the fixed effects, and block as random effects. However, there were no interactions and significant differences between the sow group. Therefore, I will show you the results of the diet as main effect. 
Moving on to the results, Pigs fed the diet with stimbiotic (in green bars) had greater apparent total tract digestibility or ATTD of dry matter in phase 2 than pigs fed the diet with xylanase (in orange bars) or the control diet (in dark blue bars). Also, Pigs fed the diet with stimbiotic had greater ATTD of gross energy in phase 2 than pigs fed the diet with xylanase or the control diet, but pigs fed xylanase had greater ATTD of gross energy than pigs fed the control diet. When we look at the ATTD of total dietary fiber, pigs fed the stimbiotic had greater digestibility of fiber at phase 2.
However, at phase 3, Pigs fed the diet with xylanase or stimbiotic had greater ATTD of dry matter, gross energy, and total dietary fiber than pigs fed the control diet. Xylanase hydrolyzes the xylose backbone of arabinoxylans, which may result in greater fermentability of insoluble dietary fiber. Xylanase may also release trapped nutrients present in the fiber matrix, making them available for absorption and increasing the digestibility of dry matter. The xylo-oligosaccharides released by the xylanase activity may act as prebiotics that modify the composition and activity of intestinal microbiota, resulting in greater activity of beneficial bacteria and greater production of short-chain fatty acids. Greater fermentation also results in lower pH in the intestine, which reduces the concentration of intestinal pathogens.  In this experiment, the stimbiotic is increasing fermentation, and we speculate that it combines the mechanism of action of xylanase and xylo-oligosaccharides.
Resulting in greater digestible energy in pigs fed the diet with the stimbiotic, both in phase 2 and 3, and also with xylanase in phase 3. 
When we look at the results of growth performance, there were no differences among groups in phase 1, but in phase 2, pigs fed the stimbiotic had greater average dairy gain followed by pigs fed xylanase, without differences in feed intake.
This results in greater gain to feed ratio in pigs fed the stimbiotic, followed by pigs fed xylanase compared to the control, and a tendency for greater body weight at the end of phase 2 in pigs fed the stimbiotic compared with the control.
In phase 3, pigs fed xylanase or the stimbiotic had greater average dairy gain, and pigs fed xylanase tended to consume more feed than pigs fed the control. Therefore, there was a tendency for greater gain to feed ratio in pigs fed the stimbiotic in phase 3.
Overall, Xylanase and the stimbiotic increased the average dairy gain, without differences in the feed intake, which results in greater feed efficiency and greater body weight at day 42. This indicates that the greater digestible energy in pigs fed xylanase and stimbiotic due to greater fermentation of fiber results in greater growth performance. 
In conclusion, pigs fed xylanase or the stimbiotic had greater ATTD of dry matter, gross energy and dietary fiber, mostly insoluble dietary fiber, resulting in greater digestible energy and greater growth performance post weaning. However, feeding sows xylanase in lactation did not influence pig growth performance after weaning.
With that, I would like to thank the monogastric nutrition laboratory and AB vista for the financial support for this experiment. Thank you for listening to this podcast and if you are interested to learn more about other topics in swine nutrition, feel free to visit our website at nutrition.ansci.illinois.edu.