Hello, and welcome to this month's edition of the Stein Monogastric Nutrition Laboratory podcast. My name is Neil Jaworski, and I'm a PhD student with Dr. Stein. And I'd like to go over the effect of a 3-strain Bacillus-based direct fed microbial on growth performance, volatile fatty acid production, carcass characteristics, and gastrointestinal tract weights in growing-finishing pigs fed low and high fiber diets. The outline that I'll follow today is that I'll begin with some previous research that really was the foundation for why we investigated the current experiment. then, I will go into the materials and methods used in this experiment, and then the results and discussion based on the growth performance, cecum and fecal short chain fatty acid concentration, carcass characteristics, GI tract weights, and then I'll go into a conclusion, and I'll leave you with a take home message. Here's some previous research I presented at Midwest meeting last year. And what we looked at was the addition of different levels of two different proprietary direct fed microbials fed at two different levels: 250 or 500 grams per metric ton. The DFM were both Bacillus-based and specifically selected for their ability to secrete a large quantity and variety of fiber degrading enzymes. And we added these to a high fiber diet with approximately 25% neutral detergent fiber. We observed that adding the DFM increased total volatile fatty acid concentration in the feces of growing-finishing pigs, which you see in the left hand graph. And this corresponded with an increased gain:feed in the growing-finishing phase, shown on the right hand graph. And what this indicates is that the direct fed microbials added to a high fiber diet increased the fermentation of this diet, increasing the volatile fatty acid production, which the pig can utilize as an energy source, and therefore, gain:feed is increased. Based on that previous research, the objective of this current experiment was then to determine the effects of a 3-strain Bacillus-based direct fed microbial added to low or high fiber diets on cecum and fecal volatile fatty acid concentration, growth performance, carcass characteristics, and GI tract weights. We randomly allotted 160 pigs to a 2x2 factorial design with initial body weight of approximately 27 kg. And the two factors of the design were two different diet types, low or high fiber, and two levels of direct fed microbial, or DFM, fed at 0 or 60 grams of DFM per ton of feed. And there were three experimental phases: the grower, from day 0 to day 35; the early finisher, from day 35 to 70; and the late finisher, from day 70 to 94. On day 94, at the end of the experiment, all pigs were scanned using ultrasound at the time of pig weighing. And then one pig per pen was taken to the Meat Science Lab, where we harvested them and determined carcass characteristics, cecal and fecal volatile fatty acid concentrations, and GI tract weights. Here is an example of the early finisher diet. And the grower and late finisher diets follow the same trend, so I won't go over those. The low fiber diets contained corn and soybean meal, and no DDGS or wheat midds. And within the low fiber, we had a diet without and with direct fed microbial. And then our high fiber diets replaced some corn and soybean meal with 30% DDGS and 10% wheat middlings. And again, we had a diet without and with DFM. This is the energy and nutrient composition of the early finisher diets. And as you can see, for net energy, the low fiber diets contained more calculated net energy compared with the high fiber diets. Therefore, we did not formulate the diets to be isocaloric. Also, you can see that the crude protein was greater in high fiber diets than low fiber diets, and therefore, these diets were not isonitrogenous. However, SID lysine were the same between all the diets. And this is because we formulated the diets to be equal on SID indispensable amino acid basis. And then if we look at our fiber levels, our ADF and NDF are much greater in the high fiber diets, and then for soluble dietary fiber, it's only a slight increase when we move from the low to the high fiber diets, and then again our insoluble and total dietary fiber are about 10% greater in the high fiber diets compared with the low fiber diets. We utilized the Mixed procedure of SAS, and the model was a 2x2 factorial design, with the fixed effects of diet type, DFM, interaction of DFM and diet type. And then the random effect was group and replicate. Now, we'll move into the results and discussion. Here is the body weight of pigs at each experimental time point. First, let me take a moment to set up the graphs. The orange bars are the low fiber diets, and the green bars are the high fiber diets The bars with the checkered pattern are the diets with direct fed microbials added to the diet. And what we observed was that at every single time point, there was no difference between the pigs fed these experimental diets in body weight. And remarkably, at the end of the experiment on day 94, all pigs weighed 109 kg on average between the treatments. And this is quite remarkable, and indicates that pigs fed high fiber diets are capable of reaching the same body weight as pigs fed low fiber diets. So how did pigs maintain their body weight throughout the experiment, equal amongst the dietary treatments? Looking at average daily feed intake, we see the main reason why high fiber fed pigs were able to maintain their body weight equal to their low fiber contemporaries. From day 0 to day 35, high fiber fed pigs consumed more feed than the low fiber fed pigs. And this was true for days 35 to 70, as well as overall throughout the entire experimental period. And again, remember, these diets were not formulated to be isocaloric, so this was expected that the pigs fed the high fiber diets would need to consume more feed in order to maintain their growth similar to their low fiber counterparts. And indeed, these pigs were able to consume enough feed to maintain that performance. Now, looking at average daily gain, we observed that high fiber fed pigs had a greater average daily gain in the growing period compared with low fiber fed pigs. And this may be due to compensatory growth, because these pigs were fed these diets from weaning. And so at the end of the nursery phase, when they were moved into the grower, high fiber fed pigs were actually a little bit slower growing and lower body weight compared with their low fiber counterparts. And therefore, during the growing phase, they were finally able to consume enough feed in order to compensate for that low growth, and actually increase their growth above their low fiber counterparts. And finally, if we look at the overall period, in terms of average daily gain, there was no difference amongst low fiber or high fiber fed pigs, as well as there was no effect of direct fed microbial addition to either low or high fiber diets. Now, if we look at the gain:feed on a kg gain/kg feed intake basis, we observed that during the late finishing period and overall, high fiber fed pigs had a decreased gain:feed compared with low fiber fed pigs. However, we have to remember that these diets were not formulated to be isocaloric, and therefore this would be expected because the high fiber fed pigs would have to consume more feed in order to consume a similar amount of calories as their low fiber counterparts. So now, if we look at the gain:feed on a kg/Mcal net energy intake, we observed that during the growing period, high fiber fed pigs actually were more efficient than their low fiber fed counterparts. And also, during the late finishing phase, high fiber fed pigs were not quite as efficient as their low fiber counterparts. But, overall, from day 0 to 94, there was no difference due to the addition of high fiber diets fed to pigs on gain:feed when looked at on a kg/Mcal net energy basis. and this is quite remarkable, and indicates that high fiber fed pigs can be just as efficient as their low fiber fed counterparts during the growing-finishing phase. and again, there was no effect of direct fed microbial addition to low or high fiber diets on the gain:feed of pigs, which is in contrast to our previous research that indicated that gain:feed during the growing-finishing period increased due to the addition of direct fed microbials to a high fiber diet. Moving on to the concentration of short chain fatty acids presented in mcg/g of dry feces or cecal digesta. So we have the cecal digesta on the left of the graph, and the fecal matter on the right side of the graph. And again, our bars are similar to the previous graphs. And here, we observed that pigs fed low fiber or high fiber diets with the addition of direct fed microbials actually decreased the concentration of short chain fatty acids in cecal digesta compared with no direct fed microbial. And this is in contrast to our hypothesis and our previous research that indicated that the addition of direct fed microbials to high fiber diets increased the concentration of short chain fatty acids. It's also interesting to note that there was no effect of fiber on cecal digesta concentration of short chain fatty acids. Again, we expected that high fiber diets would need to be fermented more, and therefore you would have greater short chain fatty acids in cecal digesta, and also the feces of pigs. And again, here, in contrast to our hypothesis, the concentration of short chain fatty acids in the feces of low fiber fed pigs was actually greater compared with their high fiber counterparts. And what that indicates is that on a mcg/g of dry matter basis, fermentation is greater in low fiber or corn-soy diet compared with the high fiber diet containing 30% DDGS and 10% wheat middlings. But, we have to remember that high fiber diets are less digestible compared with low fiber diets, as well as the fact that pigs consuming the high fiber diet had increased feed intake and therefore would have increased substrate moving through their gastrointestinal tract. And because of this, we may need to correct our short chain fatty acid concentration data, and present it on a g/day dry matter basis. And so, in a subsequent study to this one, we determined the digestibility in similar low and high fiber diets with the addition of direct fed microbial. And using that digestibility of dry matter and the average daily feed intake determined in this experiment, I calculated the fecal excretion in kg/day of these pigs. And we observed that high fiber fed pigs excreted more feces compared with low fiber fed pigs. And therefore, if we correct our cecal and our fecal short chain fatty acid data and present it in g/day – taking into account the amount of feed that they're consuming, the digestibility of the diet, and then the feces excreted – we observe that high fiber fed pigs had increased cecal and fecal concentrations of short chain fatty acids in g/day. and therefore, this may be one reason why high fiber fed pigs are able to increase feed intake but still maintain their growth performance throughout the growing-finishing phase: because they're getting more energy though fermentation. Now, we'll move into the ultrasound measurements taken on day 94 of all 160 pigs. We observed that the backfat thickness was decreased in high fiber fed pigs compared with low fiber fed pigs, indicating that high fiber fed pigs had less energy available to be deposited as lipid, or backfat, compared with their low fiber counterparts. When we looked at the longissimus muscle depth, we observed no difference due to the addition of direct fed microbial or low or high fiber diets fed to pigs. And what this indicates is that protein deposition was not affected due to fiber level or the addition of direct fed microbials. Again, looking at the longissimus muscle area, and also the calculated carcass leanness, we observed no difference due to fiber level or the addition of direct fed microbials to the diets – again, indicating that these diets were adequate in their SID indispensable amino acid levels and protein deposition was unaffected by dietary treatment. However, when we look at the fat free lean percentage, we observed that the addition of direct fed microbials to low and high fiber diets decreased the fat free lean percentage of these pigs, indicating that somehow the addition of direct fed microbials is increasing the amount of energy obtained by the pig, and therefore there's more energy available for lipid deposition, which would decrease your fat free lean percentage. Now we'll move into measurements taken at the Meat Science Laboratory on one pig per pen, so a total of 60 pigs. First, we'll begin with the slaughter weight. And what we observed is that there was a tendency for direct fed microbials to increase the slaughter weight of pigs that were selected to go to the Meat Science Lab. And due to this, there was also a tendency for the addition of direct fed microbials to the diets to increase the hot carcass weight of these pigs. However, this is due to the selection criteria, because if you remember, the ending body weight of pigs was all at 109 kg and there was no effect of direct fed microbial. Our selection criteria was based first on sex within replicate. So we selected the same sex within replicate to make sure that sex was even across all dietary treatments. Our second selection criteria was the pig with the body weight nearest the pen average body weight. And due to these two selection criteria, in some cases, the mortality within a replicate and in a pen left us with only one pig to choose from that was within that sex within that pen. And therefore, that may have increased our slaughter weights compared with our end weight on day 94. And so we do not believe the direct fed microbial effect on slaughter weight and hot carcass weight to be true. And, if we move on to dressing percentage, we observed no effect of the addition of direct fed microbials to dressing percentage. And we believe that if direct fed microbial addition to the diets truly did increase slaughter weight and hot carcass weight, we would have picked up a difference due to direct fed microbial in the dressing percentage. However, we did observe that high fiber fed pigs had a decreased dressing percentage compared with their low fiber fed counterparts. So why was dressing percentage decreased in high fiber fed pigs? Well, if we look at the GI tract weights as a percentage of body weight, we observed that the large intestine was greater in high fiber fed pigs compared with low fiber fed pigs. And due to this, dressing percentage was reduced. Interestingly, mesenteric fat was increased in low fiber fed pigs compared with high fiber fed pigs, again indicating excess energy that was deposited as lipid in low fiber fed pigs compared with high fiber fed counterparts. And again, looking at the fat free lean percentage, this time in kg on the left and percentage on the right, and again taken at the Meat Science Laboratory and not calculated based on ultrasound measurements, we observed no difference in the fat free lean in kg – again, indicating adequate protein deposition and protein supply and that our SID indispensable amino acid formulation was correct. But, again we observed fat free lean percentage to be reduced in pigs fed diets containing direct fed microbials, again indicating that the direct fed microbials may be increasing the energy supply or decreasing the maintenance energy requirement of these pigs, making more energy available for lipid deposition. So in conclusion, we observed that high fiber diets increased overall average daily feed intake, which was expected because the diets were lower in net energy. But, there was no difference in gain:feed on a kg/Mcal net energy basis compared with their low fiber counterparts. We observed decreased concentration of VFAs per gram of feces, indicating that these high fiber diets containing 30% DDGS and 10% wheat middlings are less fermentable compared with low fiber diets, or just a typical corn-soybean meal diet. However, we observed increased concentrations of volatile fatty acids per gram of feces excreted per day in high fiber fed pigs, and this may explain a greater energy supplied by volatile fatty acids in pigs fed high fiber diets compared with low fiber diets. We also observed a decreased backfat thickness and mesenteric fat, which indicates a reduced amount of energy available for lipid deposition. And finally, we observed a decreased dressing percentage due to the increased weight of the large intestine of high fiber fed pigs. And to conclude, with the addition of a 3-strain Bacillus-based direct fed microbial to low or high fiber diets, we observed decreased concentration of short chain fatty acids per gram of cecal digesta. And we also observed decreased fat free lean percentage in these pigs, which indicates increased energy available for lipid deposition. And so the take home message is that pigs fed diets with a Bacillus-based direct fed microbial had decreased fat free lean percentage, indicating an increased amount of available energy, but this was not due to increased short chain fatty acid production or increased fermentation. We would like to acknowledge DuPont and Danisco Animal Nutrition for project funding. And this concludes this month's edition of the Stein Monogastric Nutrition Group podcast. thank you.