Slide 1 Good afternoon. I am Hans H. Stein, and I'm a professor in the Department of Animal Sciences at the University of Illinois. And I would like to talk a little bit today about different aspects of fiber nutrition in pigs. Slide 2 Our interest in studying fiber nutrition actually started with studying energy nutrition. Because, as you can tell from this slide, there is quite a bit of energy in many of the corn co-products that we feed to pigs. So we can see here that both distillers dried grains with solubles (or DDGS) in the yellow bar, and high protein distillers dried grains (or HP-DDG), in the blue bar, and corn germ in the orange bar here, they all contain considerably more energy than corn. Slide 3 However, when we feed these corn co-products to the pigs, we see that in particular DDGS and corn germ, they are not nearly as well digested in terms of energy utilization compared with corn. So where the apparent total tract digestibility of energy in corn is close to 90%, we only have a digestibility value for DDGS and corn germ that are down in the mid-70s. And HP-DDG has a digestibility of energy that is closer to corn. So, it's clear that although we have a lot of energy in DDGS and corn germ, the pigs don't utilize that energy very well. Slide 4 And the reason for that is that we have relatively high concentrations of neutral detergent fiber, or NDF, in these co-products. And we can see in particular here that in DDGS, the concentration of NDF is close to 25%, and in corn germ, it's close to 20%. And that is much greater than in corn, where we only have about 7% NDF. The relatively high concentration of fiber in DDGS and in corn germ is the reason why the digestibility of energy in these co-products is much less than it is in corn. Slide 5 The negative impact of fiber on the utilization of energy has also been illustrated in work with wheat DDGS. And in this work, the ATTD value (apparent total tract digestibility) of energy is predicted as 85.7 minus 1.6 times the concentration of ADF, and ADF illustrates the concentration of fiber in these products. Also called acid detergent fiber. And we can see here there is a negative value in front of ADF. That means the more ADF there is in the ingredient, the more negative is the impact on the total tract digestibility of energy. So that's the same as we saw before for corn DDGS. And these authors also provided a prediction equation for the total concentration of digestible energy, or DE, in wheat DDGS. And again, we see here there's a negative value in front of ADF, indicating that the more ADF, or the more fiber, we have in the ingredient, the lower is the value for digestible energy in this ingredient. So, once again, we see that the more fiber we have in an ingredient, the lower is the energy digestibility and the energy concentration. Slide 6 So let's look at some of the nutritional consequences of dietary fiber. Slide 7 The total tract digestibility of total dietary fiber, or TDF, in corn DDGS is illustrated in this chart here. We have determined the digestibility in three different experiments, and you see the average value for the digestibility of TDF is 47.3%, and the lowest value is 29.3, whereas the greatest value is 57%. So, what this shows us is that the fiber in DDGS is actually not very well utilized. On average, less than 50% of all the fiber is utilized by the pig. And that is the reason why the energy digestibility is reduced when we have more fiber in the diets. Slide 8 However, we can differentiate between the insoluble dietary fiber and the soluble dietary fiber. And you will see that the insoluble dietary fiber has a very low digestibility in pigs, less than 40%, whereas the soluble dietary fiber is actually quite well utilized by pigs, and we can see here the digestibility is more than 90%. So what that tells us is that not all fibers are the same. The soluble dietary fibers are well utilized by pigs, but the insoluble dietary fibers are not. So, that also indicates that if we can solubilize some of the insoluble dietary fibers, then we could possibly increase the utilization of energy from the fiber sources that are included in the diets. Slide 9 There is also an effect of fiber on the utilization of other nutrients. Slide 10 The effect of dietary fiber on the utilization of amino acids was illustrated in an experiment by Mosenthin et al. that was published in 1994. In this experiment, there were two diets. One diet contained only soybean meal as the only source of amino acids, and the other diet contained soybean meal, but also pectin. Pectin is a rich source of soluble dietary fiber. Both diets were fed to pigs, and the ileal digestibility of amino acids was determined in both diets. The red bars here illustrate soybean meal, and the blue bars soybean meal and pectin. And we can easily see here that the digestibility of all amino acids was significantly greater in the diet only containing soybean meal compared with the diet containing both soybean meal and pectin. So it's clear from this slide that pectin has a negative impact on the digestibility of amino acids in soybean meal. And that's a concern every time we include fiber in diets fed to pigs, that these fibers and in particular the soluble fibers, they will reduce the digestibility of other nutrients as we can see here. Slide 11 The negative effect of fiber on the ileal digestibility of crude protein was illustrated in a recent experiment that was conducted in our own laboratory. In this experiment, pigs were fed diets that contained 10% casein. And all the amino acids in the diets originated from casein. The diets also contained maltodextrins and 10% of different sources of fibers. The red bar here illustrates the data from the diet that only contained maltodextrin and casein, and the digestibility of crude protein was 90.7%. However, if 10% cellulose was added to this diet, the digestibility of crude protein was reduced to 82.4%. So we can see again here that addition of fiber to a diet reduces the digestibility of crude protein. If resistant starch in the form of RS-60 or RS-75 were added to the diet, there was no impact on protein digestibility, and the same was true if soluble corn fibers were added. However, if pullulan was added to the diet, the crude protein digestibility was reduced to 87.2%. So what this tells us is that some fiber sources, but not all fiber sources, have a negative impact on the digestibility of crude protein in casein. So, when we add more fibers to the diets, we need to make sure that we don't add fibers that negatively impact the digestibility of crude protein in the diets. Slide 12 Another impact of fiber on diets is that fiber will increase the endogenous losses of fat. That was illustrated in an experiment we conducted a few years ago. In this experiment, we had both extracted fat in the form of corn oil, and intact fat that was included in corn germ. The corn germ also contains significant concentrations of fiber, so the diet containing corn germ had much more fiber than the diet containing extracted corn oil. We determined the endogenous losses of fat at the end of the ileum and over the total tract. Ileal endogenous losses are in the blue bars, and the total tract endogenous losses are in the orange bars. And we can see here that both ileal and total tract endogenous loss of fat is much greater when we added the intact fat source, and the high concentration of fiber, to the diets compared with the extracted fat where there was less fiber. So, addition of fat to these diets in the form of corn germ increased the endogenous losses of fat which results in a reduced digestibility and absorption of fat. So fiber, in this case, had a negative impact on the absorption of fat. Slide 13 There are, however, differences among genetic lines of pigs in their ability to utilize energy and nutrients. And we will see that in this experiment where we fed DDGS to three different groups of pigs. The dark blue bars represent relatively young Yorkshire pigs, the orange bars represent heavier Yorkshire pigs, and the light blue bars represent Meishan pigs. And Meishan pigs, they have a better ability to digest dry matter, energy, and total dietary fiber compared with both the light and the heavy Yorkshire pigs. And we can see that in all cases, the Meishans had the greatest utilization of fiber and energy in DDGS. What this tells us is that there are differences among breeds of pigs, and it may be possible to select pigs that have a greater ability to utilize fiber in the diets. Slide 14 There are also other factors that influence the utilization of fiber in ingredients fed to pigs. Slide 15 In this slide, we have determined the digestibility of starch in field peas. And we had field peas that were not processed, call them raw field peas, they are in the red bars. We had field peas that were extruded at 75 degrees Celsius in the yellow bars. We had field peas that were extruded at 115 degrees Celsius in the blue bars, and we had field peas that were extruded at 155 degrees Celsius in the green bars. And we determined both the ileal and the total tract digestibility of starch in these field peas. And we can see here that as we extruded the field peas, we had an increase in the ileal digestibility of starch. And that increase went from 90% to approximately 96%. However, for all these four groups of pigs fed these different sources of peas, we had some starch that escaped digestion in the small intestine. However, when we looked at total tract digestibility, there were no differences, and we will see that basically all the starch -- regardless of the processing that has been done to the field peas -- all the starch was utilized by the end of the large intestine. So all the starch that escaped digestion in the small intestine was fermented in the large intestine and therefore the digestibility of starch over the total tract was close to 100%. And this is something we see for most feed ingredients, that starch may escape digestion in the small intestine, but that resistant starch is usually fermented in the large intestine, so no starch is excreted in the feces from pigs. Slide 16 We can also look at the different fiber sources that we have in our cereals. And that varies depending on the type of cereals we work with. You will see here we have maize, or corn, we have wheat, we have barley, and we have oats. And you'll see all of these cereals contain cellulose, but for maize and wheat, there's very little beta-glucans, whereas barley and oats have significant concentrations of beta-glucans. There are arabinoxylans present in all of the cereals and we can see the concentration increases from 52 g/kg in maize up to 98 g/kg in oats. There are also other fiber components, and there is lignin in all of our cereal grains. So the total dietary fiber concentration increases from about 108 g/kg up to 298 g/kg. So what we can see here is that there are differences among our cereal grains in the concentrations of total dietary fibers. Slide 17 The physical characteristics of feed ingredients may influence how well these fibers are utilized by pigs. And the physical characteristics that we usually look at are particle size, water binding capacity, swelling properties, and viscosity. And for particle size, it has been shown many times that the smaller the particle size is, the better is the feed utilized. And that is true for fiber as well. The water binding capacity may increase as we have more soluble fiber in the diets. And that may increase the swelling also in the small intestine so more water is bound and therefore the feed in the small intestine swells more, and therefore we get an increased viscosity. And the combination of these things may be responsible for the reduction in the digestibility of some of the nutrients that we have seen may take place if we add fiber to the diets. Slide 18 If we want to improve the utilization of fiber in diets fed to pigs, we basically have two options. We can try to increase the digestibility in the small intestine, and that means we have to increase the absorption of monosaccharides from fibers. And that can only be done if we get enzymes into the small intestine that can help break down the fibers and therefore liberate the monosaccharides. There are, however, a number of C-5 sugars in the fibers, and the utilization of these C-5 sugars is very low if they are absorbed into the pigs. So, just because we increase the digestibility of fiber in the small intestine, that does not necessarily increase the utilization of energy. However, if we can increase the fermentability of the non-fermentable fiber, then we will have increased absorption of volatile fatty acids and volatile fatty acids will always help increase the utilization of energy. And in particular, if we have C-5 sugars, then it may be more advisable that these sugars become fermented so that volatile fatty acids can be absorbed. Slide 19 The utilization of fiber may be improved by chemical treatments, physical treatments, and enzymatic treatments. And chemical treatments may include ammonia treatment or other form of chemical treatments. However, while it is well known that these chemical treatments can increase the utilization of fiber in ruminant animals, there is very little evidence of increased utilization by monogastric animals. So, we clearly need more research in that area. The physical treatment we can do include several aspects of feed processing, such as extrusion or expansion or conditioning, and there is also a lack of information on the effects of these physical treatments on the utilization of fiber in diets fed to pigs. And finally, it may be possible to add exogenous enzymes to the diets and thereby increase the utilization of nutrients in fiber. Or, it may also be possible to treat feed ingredients with enzymes before they are mixed into a diet, and by that increase the utilization of fiber. Slide 20 So in conclusion... Slide 21 We have seen that there are large amounts of fibers in many corn co-products that we feed to pigs, and these fibers are poorly utilized by pigs. But it may be possible to improve the utilization of fibers by chemical, physical, or enzymatic treatments. Slide 22 We have also seen that there are wide differences in the degree of utilization of fibers in pigs. And fiber is therefore a poor descriptor of the non-hydrolytic fraction of carbohydrates that we have in our diets. And it is advisable to at least distinguish between soluble and insoluble fiber in the diets, because as we saw, the soluble fibers have a much greater utilization than the insoluble fibers. It may also be advisable to define fibers according to physical characteristics, because some of these physical characteristics will influence the utilization not only of the fiber fraction in the diet, but also of some of the other nutrients in the diet. And then it's necessary that we investigate effects of treatments on specific fractions of fiber rather than on total fiber fractions, because as we saw from the cereal grains, not all cereals contain the same fiber fractions, so that it is possible to more specifically target specific fibers if we know the combination of fibers in the diets. Slide 23 With that, I would like to thank you for your attention. If you're interested in more information, then please visit our website at nutrition.ansci.illinois.edu.