Good afternoon. So today I'd like to talk about fiber and carbohydrases and pigs. And I hope I can leave you with some take-home messages. So the first take-home message I would like everybody to remember is that fiber is really complicated. When we compare understanding fiber to understanding other nutrients such as amino acids or lipids, fiber is much more complicated to understand. And that is one of the reasons that we understand so little about fiber in general. The second take-home message is that there are some natural barriers to fermentability of fibers by pigs. And we'll talk a little bit about those barriers that are inherent to the different feed ingredients that we use in our diets fed to pigs. The third take-home message is that if we are successful in using enzymes in increasing fermentation or hydrolysis of fiber, we most likely need to use mixtures of enzymes and not individual enzymes—or at least, it will most likely be more efficient to use mixtures of enzymes. And we'll talk a little bit about that also. And the fourth take-home message is that there may be a need for new technologies to generate a breakthrough in the way fibers are fermented and to increase the energy value that pigs get out of fiber. So these four take-home messages will be the main topics of this presentation. Now let me start by pointing out that fiber actually contributes a lot of gross energy in diets to pigs. And here's an example where we have the gross energy in corn in the yellow bars and in distillers dried grains with solubles or DDGS in the blue bars. And as appears from the left side of the slide, we have almost 1000 kilocalories more gross energy in DDGS than we have in corn. However, once we have fed that DDGS and the corn to the pigs and we have determined how much is excreted in the feces and how much is excreted in the urine, then we calculate what is called metabolizable energy. And as it appears from the right side of the slide, there's really no difference between corn and DDGS when it comes to metabolizable energy. So that means that the almost 1000 kcal advantage that DDGS had in terms of gross energy somehow disappeared when it came to metabolizable energy, which is the energy that the pig can utilize potentially for production. So in other words, the DDGS energy was much less efficiently utilized by the pig compared with the corn energy. And this can also be illustrated in a different way if we calculate the amount of energy that is not utilized by the pigs. And you'll see here that in corn there's 440 kilocalories that were not utilized but in DDGS there was 1345 kilocalories that were not utilized. The main reason we have this big difference in the utilization of energy between corn and DDGS is that we have a lot more fiber in DDGS compared with corn. Corn, the majority of the energy comes from starch which is easily digested by the pig, and therefore we have only a small amount that is not digested and absorbed by the pig. In contrast, in DDGS the majority of the carbohydrates are in the form of fiber and fiber is not nearly as efficiently utilized by pigs compared with starch, and therefore we have much more undigested energy when we feed DDGS. So this also indicates to us that if we are to improve energy utilization from our feed ingredients, the high fiber feed ingredients such as DDGS has a much greater potential for improvement than the lower fiber diets such as corn, because the lower fiber diets are highly utilized in the first place whereas the high fiber ingredients are not so well utilized. So there is an opportunity to increase the utilization of energy from our high fiber ingredients such as DDGS. Let us look at what is fiber. And to understand fiber we need to understand what is carbohydrates. And carbohydrates consists of monosaccharides; and we'll talk more about the monosaccharides here in a little bit, because the monosaccharides are the building blocks of all the carbohydrates we have in diets for pigs. From the monosaccharides we can have disaccharides, oligosaccharides, or polysaccharides synthesized. The disaccharides contain two monosaccharides as the name suggests. And we have six disaccharides that may be included in diets for pigs: sucrose, lactose, cellobiose, maltose, gentiobiose, and trehalose. All of these disaccharides, as I said, contain two monosaccharides and they are connected via glycosidic bonds. And we have different types of glycosidic bonds that have effects on how well or how poorly these disaccharides are digested by the pig. And the definition of oligosaccharides are that these are carbohydrates that have more than two monosaccharides and they are soluble in 80% ethanol. And we had four groups of oligosaccharides: the galacto-oligosaccharides, which consists of raffinose, stachyose, and verbascose; we have transgalacto-oligosaccharides; we have fructo-oligosaccharides that consists of inulin and levans; and we have mannan-oligosaccharides that also can be divided into several subgroups. And then we have the polysaccharides, and polysaccharides are large structures of carbohydrates. They are many monosaccharides bound together via glycosidic bonds. And we can broadly divide them into starch and glycogen as one group, and non-starch polysaccharides as the other group. Now, try to focus on fiber. We'll see that all the structures that are highlighted in yellow here, they are what we would consider part of the fiber fraction in the diets, whereas the white components, they are non fiber fractions. And non fiber fractions—sucrose, lactose, maltose, trehalose, starch, and glycogen, they all can be digested by enzymes that the pig is secreting. And the resulting monosaccharides can be absorbed and utilized by the pig. That's a very efficient process and the pig easily gets energy out of these structures. In contrast, the fiber components that are highlighted in yellow here, they are not as easily utilized by the pig because pigs do not have enzymes that can digest the glycosidic bonds in these structures. However, the cellobiose, the gentiobiose, and all the oligosaccharides, they are soluble fiber components and therefore they are relatively easily fermented in the hindgut of the pig. So usually there's a complete fermentation of these structures in the pig. The non-starch polysaccharides, they are different because a large proportion of those components are not soluble and therefore they are much harder to ferment. So the remainder of this presentation will focus on the non-starch polysaccharides that we have in our feed ingredients. The non-starch polysaccharides include a number of different monosaccharides. We have pentoses. There are three of them that we will find in our fiber fractions: arabinose, xylose, apiose, and they all have a common structure that's C5-H10-O5. We'll talk more about these different pentoses a little bit later. We also have hexoses in our non-starch polysaccharides and fibers and those hexoses include glucose, fructose, galactose, and mannose, and they also have a common structure which is C6-H12-O6. So we have three pentoses and four hexoses. However, we also have deoxyhexoses. And deoxyhexoses are characterized by having a CH3 group at the carbon-6 position. And if glucose is turned into a deoxyglucose we call it rhamnose, and we can also have a fucose, which is mannose that turned into a deoxyhexose. So rhamnose synthesized from glucose, fucose from mannose. And we will find both rhamnose and fucose in some of our fiber structures. The structure here is C6-H12-O5. And then we have a couple of other deoxy sugars. These are called DHA and KDO, and these are seven and eight carbon sugars that are also present in some of our most complex fiber structures, and we'll talk a little bit about those later also. So we have four deoxyhexoses in total that are included in our fibers. Then we have another group that we call uronic acids, and we have three uronic acids that are included in our fibers. And these uronic acids are characterized by having an acidic group at the carbon-6 position instead of a C-H2-OH group as we have in our hexoses. So from glucose we can have glucuronic acids synthesized, from galactose we can have galacturonic acids synthesized, and we can have from methanol synthesized a compound called aceric acid. And we will find all three of these compounds in our fibers as well. And in particular galacturonic acid is prevalent in all our pectic polysaccharides that we will talk about later also. So, to sum up we had three pentoses, we had four hexoses, we had four deoxy sugars and we have three uronic acids. So that gives us a total of 14 monosaccharides that are included in the fibers that we will include in diets for pigs. So if you go back to our overview over all our carbohydrates: we talked about all the yellow structures here are what we consider fiber, and we talked about the non-starch polysaccharides is a group that is typically the most difficult to ferment for the pigs. Therefore this is a group of nutrients where the pigs obtain the least energy, so this is where we potentially can increase utilization of energy. We'll talk a little bit more about the non-starch polysaccharides. The non-starch polysaccharides include cellulose and it also includes non-cellulosic non-starch polysaccharides. Sometimes we call the non- cellulosic non-starch polysaccharides hemicelluloses—same thing. The non-cellulosic non-starch polysaccharides can be further subdivided into pectic non-starch polysaccharides or non-pectic non-cellulosic non-starch polysaccharides. And the non-pectic non-cellulosic non-starch polysaccharides include arabinoxylan, we have mixed linked beta glucans, we have xyloglucans, and we have mannans. So this group of non-pectic non-cellulosic non-starch polysaccharides include these four components and we will talk about these later also. Then we have the pectic non-starch polysaccharides, and if we look at those components, we have homogalacturonans consisting mainly of galacturonic acids, we have rhamnogalacturonans and there are two rhamnogalacturonans, rhamnogalacturonan I and rhamnogalacturonan II in our fiber fractions. We have arabinans and arabinogalactans, and we have two of those also: arabinogalactan I and arabinogalactan II, and we have xylogalacturonans. So the pectic non-cellulosic non-starch polysaccharides consists of these four components and we will discuss those later. If we take a look at the fiber components we have in cereal grains and grain co-products, then we will see that there is cellulose in these components, there's arabinoxylans, there's mixed-linked beta glucans, there's xyloglucans, there's galactomannans, and we also have lignin which is not really a carbohydrate but it is associated with the fibers in our feed ingredients and it is included in the fraction we call total dietary fiber. So, these are the different fiber components we have in our cereal grains, and as you will see later this is different from what we have in the oilseeds but we have these components in cereal grains and in cereal grain co-products. Our cereal grains include corn, wheat, barley, oats, rye, sorghum, and rice, and in this case it's polished rice or broken rice. And as we can see there is quite a bit of difference in the total amount of total dietary fiber we have in our different cereal grains, with the greatest proportions included in barley, oats, and sorghum and much less in corn and polished rice. If we take a look at the composition of fiber in corn we have here both corn and corn DDGS: corn in the blue bar and DDGS in the orange bar. And as we can tell there's 25 to 30% cellulose, approximately, in these two feed ingredients and this is a percentage of the total fiber in these ingredients. Arabinoxylans, on the other hand is almost 50% in both ingredients—so almost half of all the fiber in corn and corn DDGS consists of arabinoxylans. And then we have some other components that make up 20-25% also. So what this tells us is that arabinoxylans is the biggest component of fiber in corn and in corn DDGS, and this is true in many other cereal grains as well. But what we also can see here is that there's very little difference in the composition of fiber between corn and corn DDGS; we have about the same percentage of each component within these ingredients. And what that suggests is that although DDGS is produced after fermentation in the ethanol plant, it appears that the fermentation process in the ethanol plant does not really change the fiber composition, maybe because fiber is not efficiently fermented in these ethanol plants. And therefore we end up with all the fiber in the DDGS fraction and therefore the composition of that fiber is not different from what we had originally in the corn grain. If we look at all our cereal grains here and we look at the arabinoxylans we have present here, that's in the orange bars. We also have mixed-linked beta glucans in some of the cereal grains and we will see that corn contains very little mixed-linked beta glucans but quite a bit of arabinoxylan. Wheat has a little bit of mixed-linked beta glucans but also primarily arabinoxylan in the fiber here. Barley has more mixed-linked beta glucans but also arabinoxylan. Oats has mixed-link beta glucans and even more arabinoxylan than the others. Rye has also quite a bit of arabinoxylan and a little bit of mixed-linked beta glucans. And then we have sorghum, that is more like corn with very little mixed-linked beta glucans but a little bit of arabinoxylan. And finally we have polished rice that only contains arabinoxylan. So what we can see here is that there is quite a bit of difference not only in the total amount of fibers we have in our cereal grains but also in the composition of those fibers, where some of the cereal grains contain mixed-linked beta glucans, others contain only arabinoxylans. We also have cellulose and lignin in our cereal grains as discussed before. And you'll see here that corn, wheat, rye, sorghum, and rice has the least cellulose, in the blue bars, whereas barley and oats have a lot more cellulose than the other cereal grains. When it comes to lignin, we have a small proportion in corn and in polished rice; we also have relatively low amounts in sorghum, rye, and wheat but greater amounts in barley and in oats. So again there are differences among our cereal grains in the amount of fiber we have in these cereal grains and also in the composition of fiber. And these differences among the cereal grains will be reflected also in the cereal co-products that we use in our diet such as distillers grains with solubles or wheat middlings or oat brans or other cereal grains. Take a closer look at these different components we have in our fiber fraction. We'll start with cellulose. Cellulose is what we call a homopolysaccharide because the only monosaccharide we have in cellulose is glucose. And glucose in cellulose is connected together in long linear chains in which each glucose unit is attached to the next glucose unit using what we call a beta-1-4 glycosidic bond. And we have some parts of the cellulose that is very tightly bound; we call that a crystalline region of cellulose. We can see here the different chains of glucose are very closely related to each other and they are bound together by hydrogen bonds and therefore, they are almost impenetrable for enzymes and therefore they are very difficult to digest and ferment. However we do have some portions of the cellulose that is called amorphous cellulose. And in these portions we have the linear chains of glucose less tightly packed. They are not bound by hydrogen bonds to other chains and therefore there's easier access for the enzymes to digest the glycosidic bonds between the glucose units and therefore liberate the glucose. Now, the pig itself does not synthesize the enzymes that are needed to digest these glycosidic bonds. However, some of the microbes in the hindgut of pigs can synthesize enzymes that can hydrolyze these beta-1-4 glycosidic bonds, therefore they can liberate the glucose in the hindgut of the pigs and that glucose will subsequently be fermented by the microbes but they will synthesize short chain fatty acids that can be absorbed by the pigs. The enzymes that are needed for this hydrolysis are endoglucanases and exoglucanases. And the endoglucanases will cleave kind of in the middle of the amorphous region of the cellulose whereas the exoglucanases will start from one end and cleave off two glucose units. And these two glucose units or a little bit longer oligomers of cellulose will then be attacked by a third enzyme that may be synthesized by the microbes and this enzyme is called beta-glucosidase. And that will give the final breakdown of the cellulose structure into individual glucose units and these glucose units as mentioned can be fermented and turned into short chain fatty acids that can be absorbed by the pig. However, because of the crystalline structure of most of the cellulose, fermentation of cellulose is not very efficient in pigs. So most of the cellulose we have in our feed ingredient will pass through the pigs and end up in the feces without being fermented. But there is some of the amorphous regions that will be fermented as indicated here because the microbial enzymes can digest these beta-1-4 bonds. But in general cellulose is poorly fermented by pigs. Now if you look at mixed-linked beta glucans that we had present in some of our feed ingredients you'll see mixed-link beta glucans, they also consist only of glucose as the only monosaccharides so they are also homopolysaccharides. However the structure is a little bit different here compared with cellulose, although both cellulose and mixed-linked beta glucans consists only of glucose. Some of the regions of mixed-linked beta glucans have glucose units bound together by beta-1-4 bonds exactly like in cellulose but approximately 30% of all the glycosidic bonds are beta-1-3 glycosidic bonds instead of beta-1-4 glycosidic bonds. And that beta-1-3 glycosidic linkage induces a kink in the chain, so we don't get these long linear chains of glucose bound together. And because we don't have long linear chains, we don't get all the hydrogen bonding between the chains and therefore there's much easier access for the microbial enzymes to hydrolyze these beta-1-4 and beta-1-3 bonds in mixed-linked beta glucans. And as a result of that, mixed-linked beta glucans are practically 100% fermented in the hindgut of pigs. However, it requires two enzymes: endo-beta-1-3-glucanase and endo-beta-1-4-glucanase. But these enzymes are expressed by the microbes in the hindgut and therefore we get the complete fermentation. So mixed-linked beta glucans are relatively easily fermented by pigs whereas cellulose, that also contains only glucose is very difficult to ferment. And the reason again is that we have these beta-1-3 linkages in the mixed-linked beta glucans that makes it much more accessible to the enzymes. The bad news of course is, as we saw in the previous slides, that there is much less mixed-link beta glucans compared with cellulose in our feed ingredients. In particular in corn, we don't really have any mixed-linked beta glucans so we don't get much energy out of that fraction in corn. Whereas in some of the other cereal grains and grain co-products such as barley and oats, we have quite a bit of mixed-linked beta glucans and therefore we can get more energy to the pig out of this fraction. Now moving on to the arabinoxylans. Now we go from homopolysaccharides that only consists of one monosaccharide into heteropolysaccharides that consists of a number of different polysaccharides. And for arabinoxylans we have xylose, arabinose, glucuronic acid, ferrulic acid, coumaric acid, galactose, and also some acetyl groups involved. The structures become much more complex, but as you'll see here we have a backbone of xylose—those are the red structures here in the middle. Those xyloses are connected together by glycosidic linkages. But then some of the xyloses have side chains of arabinose or two arabinoses or arabinoxylose and then a galactose or other structures. And that makes it more complex to ferment. We also note here we have ferrulic acid and coumaric acid associated with the arabinoxylans and these two acids are phenolic acids. And the significance of having ferrulic acid and coumaric acid involved is that that opens up the possibility that lignin can be attached to arabinoxylans so arabinoxylans can be lignified which makes it very difficult to ferment. Lignin is a major barrier for fermentation in any feed ingredient and every time we have ferrulic acid or coumaric acid involved we usually have lignification which reduces fermentability. However we can try to ferment these arabinoxylans. To do that we need enzymes. One of them is endoxylanase beta-1-4, which will hydrolyze the bonds between the xylose units in the backbones and then create smaller oligomers that may be fermented by the microbial enzymes. However to get complete hydrolysis of arabinoxylans we need a total of nine different enzymes, and they are all listed here. Beta-galactosidase is needed, arabinoxylan arabinofuranohydrolases, and a number of other enzymes. So only to add an endoxylanase to the diet most likely will not help us much in terms of increasing fermentability of arabinoxylans. We will probably need more enzymes; maybe not all nine are needed because the microbial enzymes will also help us ferment these structures, but at least endoxylanases, arabinofuranosidases, and the two esterases that are needed to liberate the ferrulic acid and the coumaric acid from the arabinoxylan will be needed also. These esterases are extremely important because, as mentioned before, as long as we have ferrulic acid or coumaric acid associated with the arabinoxylans we have lignification and lignification usually precludes fermentation. But if we could include esterases that can cleave the bond between the ferrulic acid and coumaric acid and the other structures in arabinoxylan, then we could delignify the arabinoxylans and therefore increase the chance of getting the rest of the molecule fermented by microbial enzymes. Another important enzyme is the arabinofuranosidase that will cleave between the two arabinose units in the side chain. And that enzyme is important because it is believed that if there's only one arabinose attached to the xylose then the microbial enzymes can usually ferment the rest of the molecule but as long as there are two arabinose units attached to the xylose the microbial enzymes cannot ferment this structure. So getting that first arabinose unit hydrolyzed off is very important and therefore some of the enzyme companies are now combining endoxylanases and arabinofuranosidases to get this extra effect, and that theoretically should help improve fermentability of the of the arabinoxylans. Bottom line is, we have a lot of arabinoxylans in our cereal grains and cereal grain co-products. It's by far the most prevalent fiber component and complete hydrolysis of this component is pretty complicated and we need nine different enzymes. Some of them can be synthesized by the microbes in the hindgut of the pig but we probably need to include some of these enzymes in the diets. As an example of the effectiveness of using xylanases I'm showing here data from an experiment we conducted a few years ago here. In this experiment we had brown rice, we had full fat rice bran, and we had defatted rice bran. And the blue bars here indicate these ingredients with no xylanases and the orange bars indicate these ingredients with 16,000 units of xylanase. As we can see here, there was no effect of xylanase for the brown rice, and that's not really surprising because brown rice primarily consists of starch and there's only minor components of arabinoxylans here. However, full fat rice bran and defatted rice bran are produced after most of the starch has been removed and therefore we have much higher concentrations of arabinoxylans in these two ingredients. And here we can see that inclusion of 16,000 units of xylanase actually increased the amount of metabolizable energy we could get out of these ingredients, and this increase was pretty substantial: it was about 10% of the total. So we got a nice increase in metabolizable energy by adding xylanase to these two ingredients. So this is just one example that indicates that it is possible to have xylanases added to diets to increase the energy. However, it is not always we get these responses and in particular, in corn based diets and corn co-product diets, we have often been disappointed in the responses we have gotten, primarily because the arabinoxylans in corn are more substituted with arabinose than in other ingredients and therefore they a re more resistant to hydrolysis. So if we conclude for cereal grains: To really increase energy value from cereal grains, we should focus on the arabinoxylans because arabinoxylans are present at 50 to 60% of all the fibers in these ingredients. So this is true for both our cereal grains and cereal co-products. The objective of adding enzymes to these ingredients is not to obtain complete hydrolysis in the small intestine because if we have complete hydrolysis of arabinoxylans in the small intestine we will liberate xylose and arabinose. They can be absorbed from the small intestine, but they are not easily utilized by the pig so most of them will be excreted in the urine which means that the pig will not utilize the energy from those components. So instead we want the enzymes to work in the hindgut, where they can contribute to breakdown of the arabinoxylans and then the microbes synthesize short chain fatty-acids from the units that have been generated by the enzymes. And we believe it's necessary to use multiple enzymes to get measurable results. We need to have at least three enzymes, we believe: the esterases, the xylanases, and the arabinofuranosidases. If we have those three enzymes together we believe it is possible to break most of the bonds in the arabinoxylans and therefore help the microbial enzymes complete the fermentation of these structures. So that's the conclusion for the cereal grains. If we now change a little bit and talk about our oilseed meals, then we'll see that we have some different fibers here. In this case we're showing soybean meal and canola meal: soybean meal in the blue bar, canola meal in the orange bar. And in particular in soybean meal we have oligosaccharides. And we'll see that, of the total fiber, we have more than 6% oligosaccharides in soybean meal whereas we have less than 2% in canola meal. These oligosaccharides are primarily the galacto-oligosaccharides—so that's raffinose, stachyose, verbascose. More in the soybean meal than in canola meal. We also have cellulose. And again we have more cellulose in soybean meal than we have in canola meal. But then we have another group of fibers in these oilseed meals and that's the pectins or the pectic polysaccharides. We didn't talk about the pectic polysaccharides in the cereal grains because they are not really present in the fiber fractions in cereal grains, but we do have them here in the oilseeds. And we can see we have more pectins in canola meal than we have in soybean meal. And then also we have lignin as we had in the cereal grains, and we have quite a bit more lignin in canola meal compared with soybean meal. One thing to note here is that we don't have arabinoxylans or mixed-linked beta glucans on this sheet and that's because the arabinoxylans that were prevalent in the cereal grains, we don't find those in our oilseed meals. So instead we have the pectic polysaccharides. If you look at these pectin polysaccharides again we saw earlier that we have homogalacturonans, we have rhamnogalacturonans, we have arabinans which includes arabinogalactans, and we have xylogalacturonans. So these are different structures and we have rhamnogalacturonan I and II and arabinogalactan I and II. As you'll see in a second, these are pretty complicated structures. The cellulose that we have in the oilseeds are similar to the cellulose in the cereal grains so we won't talk about those again. We will talk a little bit about these pectic polysaccharides. If you look at the homogalacturonan, which is the most simple form of these pectins, this is a structure where we have galacturonic acid in the backbone. And galacturonic acid was one of the three acidic monosaccharides that we talked about previously. And then we have this backbone of galacturonic acid, and we have some methyl groups and some acetyl groups, and the number of methyl groups and acetyl groups may vary. And that gives some of the functional structures that we get from pectins. There's a total of six enzymes needed for hydrolysis of these pectins, but all of these enzymes are expressed by the microbes in the hindgut of pigs and therefore homogalacturonans are easily fermented by pigs. However, we don't have much homogalacturonan in our typical feed ingredients. We may find some if we feed sugar beet pulp or citrus byproducts but other than that we don't find a lot of homogalacturonan in our feed ingredients. However, we do find rhamnogalacturonans. And here we have rhamnogalacturonan I. And we'll see in this case we have a backbone of galacturonic acid and also of rhamnose. And rhamnose was one of the deoxyhexoses we talked about before. So we have this combination of galacturonic acid and rhamnose in the backbone and then we have some very long side chains attached to the backbone. And these side chains contain primarily arabinose and galactose, but there are also other structures included here. These can be very long and the side chains can be further substitute with side chains to the side chains, so these structures become very complicated. They are very difficult to ferment for the microbial enzymes. There is a total of eight enzymes needed for this fermentation but the microbial enzymes are relatively poor in fermenting these structures and therefore we don't get a lot of these rhamnogalacturonan I fermented in the hindgut. We also have rhamnogalacturonan II, and that is even more complicated than rhamnogalacturonan I. In this case the backbone is only with galacturonic acids. And then we have some very long and very complicated side chains that includes a number of different monosaccharides and we can have up to 14 different monosaccharides involved in rhamnogalacturonan II. We find quite a bit of rhamnogalacturonan II in our canola meals and some of the other oilseed meals and these structures are very unfermentable—we don't see a lot of fermentation even if we have all the microbial enzymes present in the hindgut. These are very resistant to fermentation. So the more rhamnogalacturonans we have in the diets, the lower fiber fermentation usually will be, and the lower is the utilization of energy from fiber in the ingredient. And that's why we always see a lower digestibility of energy in canola meal compared with soybean meal, as an example, simply because we have these rhamnogalacturonans that are unfermentable in the canola meal fiber. We also have arabinogalactins. We don't have a lot of those in our feed ingredients, but they may be included in the oilseed meals. These are divided into arabinogalactan I and arabinogalactan II. And as you'll see here, arabinogalactan I is a structure where we have beta-galactose in the backbone and then we may have a few arabinoses side chains. These structures are not difficult to ferment, they're relatively simple, and there's four enzymes needed and the microbes in the hindgut will express these enzymes and therefore they will ferment these structures. Arabinogalactan II is more complicated but again, we have the galactose backbone but here we also have some galactose side chains and then we have substitution of the side chains with arabinoses. And therefore the structure becomes more complicated. But again we need four enzymes, and in general the microbial population in the hindgut usually will express these enzymes and therefore there's at least partial fermentation of the arabinogalactans in the hindgut of the pigs. So, you've seen here that oilseed fiber is different from the fiber we find in cereal grains and these are different structures some of them are very complicated and very unfermentable whereas others are more fermentable. Conclusions we can make from this is that we have pectic non-starch polysaccharides in the oilseed fiber—in fact, those are the major components in most of our oilseeds. And some of these pectic non-starch polysaccharides such as the rhamnogalacturonans, they are very unfermentable and difficult to degrade. The structures of these pectic polysaccharides are very complicated and therefore multiple enzymes are needed for us to increase fermentability of these complicated fibers if we were to do that. However, at this point, the pectic polysaccharides are not really the focus of commercial enzyme companies so we don't have a lot of commercial enzymes that are targeting these pectic polysaccharides and therefore we don't really focus on these structures when we talk enzyme supplementation of diets. However in the diets we usually feed to pigs, we almost always have oilseed meals included. That means we almost always have these pectic polysaccharides and other complicated fiber structures from oilseed meals included in the diets. So maybe to increase energy utilization from these ingredients, we will need some of these enzymes to help us in the future. So that's the conclusion from the presentation and I hope this has given a small overview over the complicated structures that we have in some of the feed ingredients we use in our diets fed to pigs, and some of the requirements that have to be met if we expect exogenous enzymes to work in our feed ingredients. I want to acknowledge all the students and technicians and postdocs in my group who have been helping me with these studies and who have also helped put together these slides. And with that, hank you for listening.