Slide 1 Hi, everybody. My name is Oscar Rojas, and today I have the pleasure to talk about the effects of reducing the particle size of corn on growth performance and carcass characteristics of growing and finishing pigs. Slide 2 This is the outline of the presentation. I will start with a brief introduction, talking about the importance of grinding. And then, we're also going to review the recommended particle size of corn. And then we'll see, really quick, the results of two digestibility experiments, and then we'll move on to the growth performance experiment. And I will finish this presentation with some overall conclusions and the implications of this research. Slide 3 So, why do we grind feed ingredients? Grinding of feed ingredients is used to decrease the particle size and increase the energy and nutrient digestibility and thereby reduce the impact of feed costs on the total cost of the production. The recommended particle size of corn is between 600 and 650 microns. And this can be accomplished by using either roller mills or hammer mills. Slide 4 However, now the industry is moving forward to use a combination of those two systems – roller mills and hammer mills. And it is believed that this new system is more efficient of grinding. Slide 5 However, we need to be aware that there are some problems when we want to reduce the particle size of corn. We need to be aware that possibly the energy costs at the feed mill could increase, because the machines that we use to decrease the particle size will need more electricity. Also, at the farm level, flowability can be affected as we reduce the particle size of corn. And also, there are some arguments that when we reduce the particle size of corn, there is a tendency to increase the incidence of ulcers in the stomachs of the pigs. Slide 6 So as I explained before, reduction of particle size can be done using either roller mills or hammer mills. So in this slide, I'm going to explain how we obtained the four particle sizes for this experiment. We start with an initial batch of corn. Slide 7 And then this corn was first rolled, using a roller mill, Slide 8 and then, all this batch was hammered, using hammer mills, Slide 9 to obtain the final particle size of 865 microns, 677 microns, and 485 microns, and the last treatment, 339 microns. Slide 10 In this slide, we can see the AID of starch. We have in the y-axis the percentage, and we have in the x-axis each of the four particle sizes of corn. And we observe here clearly, that as we decrease the particle size of corn, there is a linear increase in the digestibility of starch. We have in 865 microns 89%, and as we decrease the particle size of corn to 339 microns, digestibility of starch increase until 96.6%. Slide 11 When we look at the metabolizable energy on a dry matter basis, we observe the same pattern as we observed in the previous slide. We observe that the energy increase as we decrease the particle size of corn. Slide 12 So the objective for this experiment was to test the hypothesis that the addition of dietary lipids can be reduced as corn particle size is reduced without affecting growth performance or carcass characteristics. Slide 13 For this experiment, we used 72 pigs with initial body weight of 32 kg. 36 gilts and 36 barrows. And we have 18 pigs per treatment. And those pigs were fed in a 3-phase feeding program. The first phase was from 32 kg to 62 kg. Second phase, from 62 kg to 94 kg. And the last phase from 94 kg to 129 kg. Slide 14 Pig body weight was recorded at day 0, day 29, day 58, and the last day of the experiment, day 93. At the conclusion of the experiment, growth performance data was calculated. We calculated average daily gain, average daily feed intake, and gain:feed ratio. And we also calculated some carcass characteristics such as dressing percentage, back fat, and hot carcass weight. And we also calculated some stomach characteristics, and we looked at the esophageal region of the stomach. Slide 15 In this slide, we can see the stomach of the pig. We observe that the stomach contains four regions. The first one, on the left, is the esophageal region, then we have the cardiac region. On the bottom right, fundic region. And the last region, the pyloric region. Slide 16 Here we can see the same stomach, but from the inside. And we observe the four different regions of the stomach, and those regions have different types of mucus. And as we observe, the esophageal region is the one that doesn't contain mucus. And this mucus is used for the stomach, as a protecting function for the acids that are produced in the stomach. Slide 17 In this slide, we can see how the lesions of the esophageal region were scored. It is important to mention than under this condition of this experiment, we did not observe any ulcers. However, we observed some lesions at the esophageal region. And this is how we scored them. We considered a normal stomach on the left. And if we move to our right, we observe a minor lesion, and then if we keep moving to our right, we observe a medium lesion, and we also observed major lesions. Those lesions were scored from 0 to 10. 0 means no evidence of lesions, and 10 means that the tissue is damaged. Slide 18 Here, we can see how diets for this experiment were formulated. And diets within each phase were formulated to have the same concentration of ME, and addition of soybean oil was adjusted to compensate for the reduction of ME that was assumed as particle size of corn increased. So if we observe, for example, in phase 1, as we decreased the particle size of corn from 865 microns to 339 microns, the concentration of oil decreased as we decreased the particle size of corn. Slide 19 The data for this experiment were analyzed using the Proc Mixed of SAS as a 2x4 factorial. The fixed effects were particle size, sex, and the interaction between particle size and sex. The random effect was the replicate. And when we looked at interactions, they were not significant except for average daily feed intake from day 0 to 29, and gain:feed ratio from day 0 to day 93. Slide 20 So now, let's move on into the results for this experiment. Slide 21 Here, we are looking at the overall growth performance from day 0 to day 93. We observe in our left the initial body weight of the animals, and on our right, the final body weight. We observed that there were no difference in the final weight of the animals among treatments. Slide 22 When we look at the average daily gain, average daily feed intake, and gain:feed ratio, we observe that for average daily gain and average daily feed intake, there were no difference among treatments. However, when we observe the gain:feed ratio, we observe that there is a linear decrease as we decrease the particle size of corn. And I explain later on why is that. Slide 23 In this slide, we can see the frequency of lesions in the esophageal region. We observe in the y-axis the percentage, and in the x-axis the four particle sizes. We observe, in orange, normal esophageal regions, blue represents some level of lesions considered minor, green represents medium lesions, and red represents major lesions in the esophageal region. So for example, if we look at the 865 microns, we observe that 50% of those stomachs were considered normal. And when we start decreasing the particle size, we observe that normal esophageal regions start decreasing, and we observe that minor, medium, and even major lesions – the incidence of the lesions starts increasing in the esophageal region. So, for example, at 339 microns, we observe that almost 30% of those stomachs had major lesions, and almost 50% of those stomachs have some minor lesions. Slide 24 When we decide to give a score to those lesions, we observe that there is a linear increase in the score as we decrease the particle size from 865 microns to 339 microns. Slide 25 Now, let's look some of carcass characteristics. Here, we are looking at the dressing percentage. As particle size decreased, we observe that there is an increase in the dressing percentage. Slide 26 And when we look at the hot carcass weight, we observe that there are no difference among treatments. Slide 27 In this slide, we can see the gain:feed ratio calculated based in hot carcass weight. And if you remember, I mentioned before that gain:feed ratio was decreased as we decreased the particle size of corn. However, when we calculate this gain:feed based on hot carcass weight, we observe that there are no difference among treatments. And the reason of this is because, if you remember, dressing percentage of pigs were increasing as we decreased the particle size. And this indicates that the GI tract of the animals were heavier in pigs fed corn ground to 865 microns compared with pigs fed 339 microns. Slide 28 Now, when we look at the back fat, no difference among treatments. Slide 29 So for the conclusions of this experiment, we observe that the increased concentration of ME in finely ground corn that has previously been reported make it possible to reduce the inclusion of added lipids in diets containing finely ground corn without negatively impacting growth performance or carcass characteristics. No negative effect, as I mentioned, on growth performance and carcass characteristics. And we need to be aware that the reduction in particle size can increase the lesions in the stomachs, but it is important to remember that under the condition of this experiment, no ulcers were detected. Slide 30 And because of the increase of ME in corn ground to a smaller particle size, it is possible to reduce fat addition in diets if corn is ground to a smaller particle size, which will result in reduced diet costs and improved profits. But remember, this reduction in particle size could generate some lesions and also, there could be some reduction in diet flowability in our feeders. Slide 31 And with this, I would like to thank you for your attention. And I also would like to invite you to go to our website to see more podcasts. Thank you.