Well, greetings. Today I'm going to talk to you about a system that I think is absolutely essential, and that is the interaction of the immune system in the gut. My name is Doctor Chris Chase and I'm in at the Department of Veterinary and Biomedical Sciences at South Dakota State University.
First, I just wanna give a little credit to those people whose slides are gonna use today and, and also particularly, you're you're gonna see one animation that came from the Immunobiology, the 8th edition. And the outline of my talk today is, is I'm going to begin with first defining for you kind of our, our latest understanding really of what the immune system is, and that's really what regards homeostasis, and we'll talk about the importance of stress and its interaction with the immune response, and then really talk about this mucosa regulation that's really essential for immune function and, and for health. And then what are the things that we can actually use to help regulate the the system so that we can actually maintain homeostasis in health.
So first of all, let's talk about homeostasis. So that's the, the process in which an animal maintains a very stable, healthy internal environment and really the, the take home here is that the main job of the immune system is to maintain health. And again, the immune system is part of that process and as you'll see, it's also involves the microbiome.
And we know that when that system is under attack by pathogens, part of the job of the immune system then is to be able then to, to fend off by using innate immunity and adaptive immunity as well. So, as I said, homeostasis is this is the idea then that the immune system job is to maintain health of the animal. And it's a partnership between the immune cells, particularly the immune cells that we'll describe in just a moment, that line the gut, and the respiratory tract, and actually the microbiome, and, and the microbiome.
The courses are the, the microorganisms that are in our respiratory tract, in our gastrointestinal tract, on our skin, we're talking about the mammary gland in the mammary gland, the reproductive tract, but it's that interaction in between those microbes that are, are the commensal organisms of this part of our system and their interaction with these mucosal cells. Typically, when we have thought about disease, we thought about disease really in the idea that the immune system's main job is to be on the defensive, rather than being proactive maintain maintain health. And as you can see, In this, in this slide, this is what I call sort of the, the classic version of, of what occurs in terms of of the immune system and its and it's, and its interactions, and that is, we think about, well, disease was a result of something that happens to the immune response.
So we had some kind of stress like the animals weaned. The, the, the cow calves or whatever it is, and so there's a dip in the immune response, and at the same time, there's, there's an increase that occurs in terms of, of the challenge. So we added new animals, we put them into an environment where their environment's not particularly clean, and all those things and of course lend themselves into increasing that load.
But one of the things that we've learned, particularly about COVID. And and and the way that that disease process works, that is in fact really was wasn't that that the SARS virus was actually the main culprit, but in fact, yes, it caused disease, but it was it turned out that things like obesity and other stressors or other, other things that resulted in inflammatory responses resulted actually in disease. And that's what I'm showing you in this graph here, the idea then that in fact, a lot of the time, in fact, probably most of the time.
What happens is that the immune system overresponds to that pathogen and we end up getting too much of a good thing. So, so not much, not as not as much of a good thing as we talked about sort of the original concept. Oftentimes disease is a result then of too much of a good thing.
And so what we wanna do then is do our very best. To maintain homeostasis and so that when we do get that immune response, which we need an inflammatory response, we need that to occur, but indeed trying to modulate that so that it's just not too much of a good thing we can maintain stay at homeostasis and the steady state. Now, a key player in this whole process is the mucosa.
So the mucosa actually, these are the cells in that line, the gastrointestinal tract, and they're particularly the respiratory tract, are actually represent the largest immune organ in the body. So it's not. Lymph nodes, it's not the spleen, it's actually these cells that line the mucosa.
And so besides being there for absorption and those kind of, of, and secretion that we normally think of what's in the GI tract or if it's a respiratory tract, being able to clear pathogens and those things with the mucciary apparatus, I think, I want you really to think about this actually being as a very active and and robust part of the immune system. So as we look at at this diagram, what you'll see there's really 4 components I want to talk about. The first component is something that's sort of very simple and one thing that we probably don't think very much, and that's just mucus.
So, mucus is, is produced by goblet cells, and then mucins are produced by these epithelial cells as well. So they both contribute to the, the formation of mucus and it varies in the intestinal tract, and it varies in the respiratory tract in terms of the thickness and the characteristics of it. So the thing about mucus is one is obviously it provides a physical barrier, but the second thing is it provides a matrix, both for microorganisms to hang out in, but also in terms of other components of the immune system that we're gonna talk about here in a second, that are produced and regulated by the, these mucosal cells.
So the second thing I want to talk about are, are these are called AMPs or antimicrobial peptides, and these are sort of the body's natural antibiotics. And they are produced by these cells, and these, again, they, and they're regulated, as is the mucus, by the presence of commensal organisms and also by signals that they'll actually get from the immune system as well. And so these antimicrobial peptides are against bacteria.
There's some that are actually against viruses, but again, they help in terms of of keeping the right balance in terms of commensal organisms, the good guys, and pathogens. So that's the second component. The third component then is our secretory immunoglobins and here we're showing you secretory IGA, but if we were in the upper respiratory tract, it would be predominantly secretory IgG, the reproductive tract, it would be IgG as well.
And so although these cells do not produce immunoglobulin, they help transport it, and as you'll you'll see in a moment, they also help regulate that because they actually will help send signals to B cells to actually increase the amount of antibody being produced so again that we have more antibody, and now again we have antibody that's specific. For different pathogens, it's again embedded in that in that matrix in the in the mucus, and it's out there again to help protect against those pathogens that are out there. So that's the third component.
We, I think of those three things, the mucus and the antimicrobial peptides and and the endoglobulin as being the kill zone. The fourth component then are these what we call tight junctions. And these tight junctions then are literally finger like projections that are regulated by calcium and by the immune system that knit cells together very tightly, so they only allow small micromolecules through, they don't allow bacteria through and they don't allow bigger macromolecules through, and they too are regulated by the immune system.
So it turns out when we have an inflammatory response, these tight junctions begin to break down. And we end up with something that we call leaky gut in the respiratory tract that can also occur, obviously it's not leaky gut there, but, but these tight junctions are essential. So those four components, the mucus, the antimicrobial peptides, and the immu globulin, together with the tight junctions and form this barrier that's very dynamic and as you can see involves innate and the acquired immune system as well as, as, as just as besides mucus and the tight junctions.
I'm gonna show you in this little movie. That in that in fact the back how how this system works. And this what I'm gonna show you in this movie is actually based on Crohn's on a type of Crohn's disease in people.
So what we see here again is we see the mucosa, we see, at the top of the of the frame, you see the, the commensal organisms, that's a lumin of the of the of the gut, and then what you're gonna see then as they're showing you there, there's the epithelial cells, and then there's the laminopropria, that's where the regulations is gonna come, we'll talk about in a little bit there you see there's tight junctions. And then you'll see that the goblet cells begin to produce a little bit of mucus here in a moment. So again, that's that first component that we that we talked about, so we'll see the production here of a of nice green mucus.
And then what we'll see is the next thing is production in of antimicrobial peptides. Now, in this particular animation, they're showing you that, you know, produced by a specific type of cell called pan cell, but it turns out that in domestic animals, basically all the epithelial cells can produce these antimicrobial peptides. So it's not just a specialised cell.
So here they're showing you again the mucus, the antimicrobial peptides. Tight junctions, and now we're we'll begin to show you how immunoglobin comes in, because again, remember, immunoglobin is not produced by these cells. But it is regulated by it.
So now you're gonna see a cell that we call a dendritic cell which will come in to the frame that you see and it'll actually sample, the, the bacteria that are actually on the surface and it's gonna bring, come in and it's gonna help regulate and tell the immune system don't overs respond to this. And it does that by sending some signals and you'll see that here, it's something called TGF beta, and these epithelial cells can do that as well and that causes that T cell to come call regulatory T cell. And what that does is that regulates the immune system so you don't have too strong of an inflammatory response.
At the same time, as you can see with that B cell, it actually causes that B cell then to increase production of immunoglobulin. So now the immunglobulin can be exported and now enhance that kill zone. Now you're gonna, we're gonna see another dendritic cell pop up in here, and it's also going to again interact and bring in some of the, of, of the material.
And now it's gonna send signals to another cell of innate immune system called the natural killer cell, which will also send signals and that too will turn on that production of antimicrobial peptides. So now you'll see the enhanced production of antimicrobial peptides. So that's so again anti-coal peptides can be turned down by the immune system and they can be turned down by conventional organisms, and we're gonna see that in just a moment.
So as I told you, this particular animation is actually based on a type of Crohn's disease. So it it turns out that some people, that, well, everybody has receptors in their epithelial cells that actually recognise different bacterial products. That's what you're seeing here, you're seeing the receptor, it's going to recognise a part of actually in this case, salmonella called myomyodipetide, and that when it recognises that, then it's gonna turn on genes and it produce more antimicrobial peptides.
And enhance the kill zone. OK, so you see that, so now that that the the epithelial cells will produce more antimicrobial peptides, enhance the kill zone, and you can help maintain the homeostasis and help of that animal. But there are some people.
They have a genetic defect in that receptor that we just saw. So when they, they're gonna zoom in on this again and what you'll you'll see this time when they zoom in, is that instead of that receptor having a kind of an open see to it, it's got a little bit of a kink in it. So we'll we'll we'll zoom on in on that, yeah, in just a moment.
So you'll see here's that receptor. Now you see there's a little kink in it. So now it can't recognise that neurbieptide.
Therefore, it can't send a signal then that will then that will then turn on the antimicrobial peptide. And so then what happens is we don't produce antimicrobial peptides. And therefore that kill zone becomes depleted and you'll see what happens then is the immune system does what it's supposed to do, it responds to the infection in this case because the kill zones depleted, so we have macromolecules and bacteria that come over and now the innate immune system kicks into gear.
One of the main things that the innate immune system does is it turns on inflammation, OK? And again, because it's job is to, to sort of stop infections in the tract, but in doing that, It creates an environment then that actually enhances, actually the, the gut becoming leaky, and oftentimes not resulting much in terms of disease, but it results in energy being directed away from the growth of the animal or the milk production of the animal and going into the immune system, because the immune system needs a lot of energy to do what you're seeing here. So again, it's responding with an inflammatory response and again we wanna try to minimise that as much as we can.
So all that is occurring actually in the in the laminarrous, so right below the mucose. All right, so let's look at the next slide. And this side, we'll we'll see, again, let's turn out the pen back on.
So here's the kill zone that we just talked about. So here's that those epithelial cells, the the mucus, antimicrobial peptides being produced in IGA along with the commensal organisms. And here then is the lamin appropriate.
So this is the regulatory part of this. This is the part then that is gonna regulate that, that key regulatory cell to help. Block any kind of strong inflammatory response and at the same time increase production of IGA.
So this, so there's really two essential things there that we need to see for homeostasis. One is enhance the kill zone, and two, is turn on this anti-inflammatory response which then blocks having too much of an inflammatory response and at the same. Time increases in secretory IGA.
So we help keep the tight junctions intact. We, increase production of antimicrolic peptides, increase that so we can take care of the pills on at the same time, we prevent the immune system from overresponding so that we don't have that inflammatory response, so we don't lose a lot of energy to turning on, that particular response. So let me just show you then that we or summarise this with this particular slide.
So on the left hand panel, what you see then. Is an animal who's who has a healthy gut and a healthy microbiome. So here what you see is you see, here's that kill zone, the antimicrobial peptides, you see IG you see lots of commensals, and again you can see the monocommensals also regulates how much mucus that we have.
And so you can see either here's some of the bad guys out here, the pathogens, but most of them are kept out, and prevented them from actually coming in. So again that we we we maintain homeostasis and health of that animal. Now that's a contrast to what we see on the right, where we have this depleted microbiome.
So it could be a cat that's been weaned. It could be an animal that's been hauled longer distances. It could be times during heat stress.
And what you can see then is that disrupts the amount of commensal organisms that we have. So now that that mucus and and . Kill zone are very depleted.
It makes it that much easier than for pathogens to come through and then us to have these inflammatory cells and therefore, we're gonna see more innate immune response and again more inflammation and again energy that's going to be taken up and, and again, it certainly can result in in overt disease as well. And we, and we call that depleted microbiome, we call that when that occurs, we call that this biosis. So again, that means then that the the microbiome then has been depleted and therefore if it's affecting the overall health of the gut, but then it also affects the overall health of the animal.
So if we think about that what's going on in the with the immune system and it's it's interaction that what it needs to do then to maintain homeostasis then is it needs to, first of all, obviously we're gonna prevent and control disease because we want to maintain health. And if there's too much of a good thing, we have immune pathology, and if there's too little of it of of a immune response, the pathogen wins. And again, the fact that we have an immune response which we learned from COVID itself is not always a good thing.
And again, we want to try to maintain this balancing act. Now the other thing that we need to be aware of is that when we have this, this, these kind of situations occur in terms of a leaky gut and this inflammatory response, it's not just a localised response. Yeah, so it may occur in the, in the GI tract, but the bottom line is that that inflammatory response and those inflammatory mediators get in through the lymph, then head to the lung, and the thing is it can go in both directions.
In other words, you could have sort of a lung infection. And that some that that inflammation is gonna go systemic and then that in turn is gonna affect the gut or it could affect the mammary gland or could affect the reproductive tract as well. And of course, those systems that they were under that had infection and inflammation, they too are gonna con contribute to this systemic effect that we can see, and, and so again, just because, you know, we have something occur locally, we need to be well aware that there's a fact often a systemic response as well.
And that really then leads to this, this syndrome that we call leaky gut again, and, and what really tips it off is this is again the idea that we have this the production and by these macrophages of the innate immune system producing this inflammatory response, which again we want them to do, but unfortunately that also results in the production of a chinase that breaks down tight junctions, and now we have a vicious circle. So again, so because now we break down the tight junctions, we have more material come across, more bacteria come across, how the immune system responds even more aggressively. So again, that's why the regulatory part is so important because again, if we can regulate these T cells and have regulatory T cells here, then that's going to help again block this too much of the inflammatory response and at the same time, you know, turning on IL 10 and some other things that can enhance the production of in lima.
And so what are the things that we can associate with leaky gut then? And again, it, it explains lots of negative consequences and not just in terms of heat stress, but any kind of off feed events, OK? So again, we have feed restriction, you have the transition period in, in, in, in, in, in cattle.
We have heat stress, we have, again, feed restriction could be because of the animals are transported hadn't eaten for some time. And then we have issues that occur in the, in the hindgut as well. They all contribute then again, so even though these are sys systemic stressors, don't contribute to leaky gut, and that in turn results in In the immune system, Responding and again that that response ends up turning on and and consuming energy that's gonna ultimately affect production.
And again, you know, so being able to get to, to help prevent that, again, and you can see that response is also in terms of metabolic response and an endocrine response as well, all again having a probably a negative effect on the productivity of that animal. And this is, you know, shows you the idea then that, if we can regulate that, and again what we're showing here is actually one of the things that the the animals are doing normally. I mean, if we have a healthy microbiome, the commensal bacteria there between either the products that they produce by breaking down things like, cellulose, another fibre, or just by the components that they produce, like we saw at the mealdieptide, they can regulate the immune system.
What we're showing here, the example is short chain fatty acids, of course, one of the short chain fatty acids, of course, is butyrate. But here what you see is a short chain fatty acids. This is a direct effect where they directly affect those epithelial cells.
The epithelial cells produce this anti-inflammatory cytokine called TGF beta, which then has the effect then of of turning down regulatory cells, so it suppresses the excessive immune response at the same time improving the production of of IGA or IgG. You can also see here that these short chain fatty acids and butyrate in particular can have a direct effect. So here you see them butyrate is readily absorbed across the intestinal tract, and here you can actually see it having a direct effect then in terms of turning on these regulatory cells again, trying to help in terms of having homeostasis and suppressing the excessive inflammatory response.
And again, suppressing that is really key to help to helping mucosa and homeostasis. So what we see then when we have too much in terms of the, of these inflammatory cytokines, and again the idea that it starts out local, but then we see a systemic response is in this list now. So the first three things that we see here, so increased sickness behaviour, so that's things like listlessness, a droopy ear, a decreased feed intake, so you have an appetence, increased body temperatures and sweats, those are things.
Commonly that we might see, for example, after we vaccinated animals, especially the first time that we vaccinated. So some of the animals may show us some of these kind of behaviours, but what that tells us is that we've turned on the innate immune system. And we, and we activate it.
So that's not a bad thing. And again, we can all probably think about when we've gotten a, a vaccination, you know, and our arm is sore and we feel a little droopy the next day. It just tells us again, that, that same kind of sickness behaviour, these first three things that we talked about, we have, you know, we have a fever or we have chills.
So again, that's, that's all tells us again that the immune system has been activated. Again, in this case, the effect that these cytokines are having are actually on the central nervous system. But, you know, as far as we look at productivity in animals and their health, we also look at these other issues.
For example, we have decreased feed conversion, decreased gain, cause again we're using a lot of energy up when we turn on the immune system, it's gonna decrease milk production. We see increased mastitis, increased metritis, increased bovine respiratory disease begin because even So, inflammation may be local, it can have a very large systemic effect as well. OK, let's talk about stress and immunity because the immune system is very susceptible to stress.
So what is stress? I get some, as you can see, it's a very broad definition. It's anything that reduces immune response capability.
And we know that as we have gone to more intensive production schemes, that indeed that that that that in itself is more stressful cause we have animals and In more dense situations, we're feeding them fairly complicated and complex diets, and we know that again that you're gonna see much more stress in an intensive operation than you will say an extensive operation where C or say I'm not a pastor. And this is just a, a list of some things again that will give us like obviously caught that stressors, and so things like, you know, weaning, movement into the into the auctions and sale yards, commingling of animals, transportation. But I wanna, you know, I'll, I'll talk specifically about dehydration a little bit later, in the importance of it and then, and then time off feed cause we, we've talked about the mic.
Microbiome, we, you know, we talk about the nutrition of the animal, but realise we're also feeding that microbiome. So that time off feed is a, is a, is a big issue. And obviously, if there's an injury, that's gonna affect the ability of the, of the animal, in terms of the feeding and watering and, and, and competition with other animals.
So we look at different factors that are that are that are involved, and, and these are all stressors from a paper actually that by Jim Wall's group at the University of Illinois, that just lists a number of things that that could be associated then with affecting the microbiome. And so we're looking at at things like And the epigenetics, the maternal microbiome, the environment, effectively heat stress, and the housing that the animals are in, the age, weaning, dietary changes, and transportation, how many animals, you know, we have together, how we commingle them, and then obviously antibiotics and vaccination, and of course the disease and pathogen exposure. Now the interesting thing is, those are the same factors that when I talk about what affect the immune response are these same kinds of things that we know that, so those two back in the microbiome and the immune system working together, the stressors, guess what, are the are are are in common because again they, they have an effect on both systems.
So again, that causes us a major issue in terms of how can we minimise these stressors so that we can help maintain homeostasis and health in that animal. Now, the example that I want to use is bovine respiratory disease. So we'll talk about that in, in this particular little slide.
So, you know, normally, we think about sort of three groups of pathogens that are associated with bovine respiratory disease, and they, they, of course, are viruses, mycoplasma, which again is a type of bacteria, but then, and then bacteria like Manhy and And again, we're thinking about in terms of from the bovine side. And typically, if we look at viruses, viruses by themselves typically result in relatively uncomplicated disease. So if the animal's not stressed, it'll be pretty uncomplicated.
We know that the viruses can interact though, and, and by causing damage and that damage that makes it easier for mycoplasma and bacteria to take advantage of that and we'll get bacterial pneumonia. And again, those, those, you know, they, and they interact and oftentimes we'll have both bacteria and mycoplasma interacting together and particularly as the disease becomes even more chronic. And then you add on to that, then what can you do to the immune system?
So these are the stressors and so now the immune system job is to protect against these, but now if I, if I have the animal under a series of stressors, so this could be, in this case, you know, physical stress, so in terms of, How far the animals have to walk, the, the footing that they're on, and then environmental stressors in this case being the, the cold, the dampness, those things that are, that are in the heat in, in the, in there, those things are all gonna have a negative effect on the immune system. So the immune system is not gonna operate at the level that it needs. And we know the other thing is, we're talking about these stresses, but we also know that these pathogens too have abilities to actually have a negative effect on the immune system as well.
So, the immune system has lots of things sort of working against it. And then, the other thing that we, you know, we need to be aware of then is that not just in terms of the physical stress, but then psychological stress. In this case, these are things where we often we're talking about temperament.
So we have animals, that, that are, particularly have a lot of flight in them, you know, they're, they're fearful. Those animals, turns out the product, production of norepinephrine. Ends up being a major negative influence on the immune system.
And the other interesting thing about norepinephrine is that norepinephrine actually will make bacteria, and certainly gram-negative bacteria actually grow better. So not only does it have a negative effect on the immune system, it has a positive effect on the bacteria. So again, just helping, you know, abrogate and make the opportunity for bacterial pneumonia to be even, even stronger.
And then the other thing that we need to think about, and again, you know, oftentimes, and again, I'm a person who does a lot of work with vaccines, and vaccines are important, but vaccines can also contribute as a stressor on the immune system. So given at the wrong time, where we've already got, say, transportation stress or when animals are off feed or off water, and now vaccine at that time is just not a good time or or or a transition period. It's just not a good time to vaccinate animals and that vaccine may add to the stress as well.
Now, one of the key things that's involved in in this whole pathway, in terms of this of of stressors and stressors are particularly have an effect, particularly on macrophages, and they affect a pathway called and and again I apologise for for throwing an acronym out here, but it's called NF k Kappa Beta. And NF kappa beta is an important regulator in, it's in all cells, but in particularly in macrophages that first of all, it enhances the inflammatory response and that's what we're seeing here. So now we have more inflammatory cytokines, and here you see that TNF again, the one that we associate with leaky gut being produced.
Another thing that happens is that it Causes these macroli to become even more activated, OK. So, first of all, they produce it and then what happens when they produce these cytokines, it makes them even more what I call angry. And then, and then, and then what they end up doing is they end up recruiting more neutrophils.
And the other thing that happens is that neutrophils, which normally, and I'll show you that in the movie here in just a second, that these neutrophils nor what they should do is take up bacteria, and shrink up and disappear. And what happens in this scenario though, when they, when there's inflammatory status is going on is that they undergo what we call anti apoptosis which means instead of shrinking up and just kind of going away and not causing inflammation, they actually will explode and release their contents. And they will also recruit more neutros.
Now, it turns out that, you know, that's, that's probably a, a good in most organs of the body with the exception of the one. So if you recruit neutrophils into the intestinal lumen, they have an escape pattern. You escape route, you recruit them into the mammary gland, they have an escape route.
If you recruit them into the reproductive tract, there's an escape route. You recruit them into the lung and, and these cells only have a half-life of 6 hours. There's no place for them to go.
And so one of the things that will happen again if they are under this inflammatory environment, is that they will, they release their contents which will kill the bacteria, but will also cause collateral damage. So let me show you that with this little movie. And so I've seen here, these are all neutrophils, and what we have here, this is an aspergilous filament, so it's a fungal filament.
And what we'll just see then is we keep if you keep your eye on on this cell right here, you see it start to get to shrink up. And then because it can't do what it needs to do against this aspergillu it actually goes in the opposite direction. Now you see get very large, and what you'll see is it looks like a little atomic bomb here, and it releases its contents, and it blows up, and it releases those contents.
And those contents will kill the aspergillus, but unfortunately, they're also gonna cause an inflammatory response and they're going to cause collateral damage. So it's not unusual then, to see. Eamel whose lung had that occurred to it.
So here's this is a lung enamel with fibrinous pneumonia, which probably the night before was normal. And what you see here is again, these are all acute phase proteins that have been activated because of the liver was activated with the inflammatory cytokines going on, and we end up with this very severe fatality that occurs again because really of too much collateral damage and too much activation of the immune system again, too much of a good thing. Now, let me just talk a little bit more kind of in a stepwise process how that could happen.
So again, this is looking at the respiratory tract and again this idea that we're gonna have, you know, we have this stress and then along with this biosis and how that can contribute then to, you know, to what, to what we, what we can see. So here you, we begin with, if you look in the upper respiratory tract of this, of this animal, what you see is what we call a microbiome and equilibrium. So you see there's green dots and red dots and yellow dots and so, so there's a good equilibrium there.
But if you now put this animal under stress, so you wean it, you dehorn it, you castrate it, you run it through transportation, mixing with other cow in the auction market, you can mix it with other cows, because there's stress, there's steroids being produced, and of course the opportunity for that viral infection, which normally is on its own, it's not particularly, you know, if there's not any other stresses going on, isn't, isn't particularly caused much morbidity. In this case, what happens, we begin to see what this biosis. So we have displacement then of the, of, of the good commensal organisms, and now we have the colonisation and overgrowth of the pathogens.
They're the red guys. OK. And then on top of that, again with more stressors, so we have dehydration, vitamin mineral deficiency.
We have a heat stress, there's dust, so any of these things, they're gonna impair the ability of the trachea to clear those bacteria, so that makes the bacteria easier to get down into the lung. And what do we end up with? We end up then with bacterial pneumonia.
So again, now you can see how stress along with that, this biosis, in this case, the effect on the microbiome of the respiratory tract then can result in in disease. So let's talk a little bit more specifically in using BRD as an example. On respiratory disease of of four particular conditions that can that are stressors that and, and what they can do.
So we'll talk about dehydration, heat stress, vaccination, and then over conditioned animals. So this is a paper that from back in 2013 by John Richard's group, who's John's not at at West Texas A&M, and what they looked at here was, was cattle, that were would be around a couple 100 kilogrammes, then transported a long way so what we call high stress animals, or high risk animals. And when the animals arrived, what they did was They pulled, and these are 4 different studies that they pulled together, and a day after arrival, they took a single blood sample, the CBC, so they looked at all the red blood cell and white blood cell differentials.
They also then vaccinated the day after arrival, and also treated them for anti-hemetics, and then they also gave them the metaphylaxis antibiotics. And if they were a bull, they also did castration. So you see half of them were bulls, and half were steers.
And then they follow those animals through to see whether or not they develop boma respiratory disease. And so what they've been so let's say get the single blood sample and then they look to see whether or not they got BRD. And so one of the things that they, they certainly showed that was a, you know, had was a big factor was the source of the animals, OK?
And then they obviously they looked at castration status, so you not surprisingly the fact that the animals were castrated and after arrival, that would be result in more respiratory disease and you can see it, they're about 3.3 times more likely to develop bovine respiratory disease that they were castrated. Then the other thing that they looked at, because remember I told you the differential, they found out that if these animals had higher yosinophils, and we know that yosinophils actually indicate if they're higher, in this case higher is only like 3 or 4%.
It's not like 10%, that would be a parasitammia, but if there's, if they're higher, that indicates that the animal has is in a better position to actually deal with a with a with an inflammatory response. And what they found was, is that if they had had a higher sins. Actually 2.6 times less likely to develop bovine respiratory disease.
So in this case, telling us how important an anti-inflammatory response can be. And then the last thing that they, that they looked at that they, they noted was the effect then of dehydration. OK.
In this case, if the animals are dehydrated, it was actually the odds of them developing bovine respiratory disease is actually 3.6 times higher. So it's even higher if the animals were dehydrated.
Than if they were castrated. OK. So again, just showing you the importance of hydration in animals again, so that, in this case, it was actually the biggest risk factor that they found in this study was whether or not the animals are dehydrated.
And again, you can think about the mucus, you can think about the fact that immune cells have to move. So dehydration is a big issue in terms of the ability of, of both of the barrier to be maintained and for the immune system to respond. All right, here's another study.
This is done in young calves, and all they did in this study was to to look at the difference of whether or not these calves got watered the day they were born or 17 days after. This is from Iowa State, and what they found in this study was that If they got water at at day 0 versus at day 17, that actually their milk intake was higher, OK? And, and they actually, and, you know, and, and as you follow them across, it actually was smoother in terms of their intake, than enamels they got water at day 17.
So that was one of the things they noted. Another thing that they noted then, again, if you see the other One thing that happened because they started right at the beginning that, one of the things that happened was because, again, on day 17, this is total water intake. This includes in, in the milk.
And all of a sudden that these guys, you know, had a, had a, had an increase, which was, you know, was basically significant as well. And in spite of that, I mean, these animals didn't have more diarrhoea. They actually, they had, these animals actually had higher faecal scores than the animals that, that got the water right from the start.
And then when they looked at, and again, and here you see the, again the intake. So again, the, the, the calves they got from day 0 can see sort of a steady intake that occurred with it. And actually you look at at growth in these animals, the animals again that had the got the water, day 0 had had had better growth than the animals that got at day 17.
So again, in this case, just getting water earlier. Made a difference. And the other interesting thing, and this is actually from this person's, OK, so here's the summary.
So the AIDS first offered did not have an effect on intake, severity of duration of disease, but it, but what it did do is that it, it improved growth performance, both pre and post weaning, again, possibly through a positive effect on lumen development and thus on, on the nutrineization. So one of the things that they, they found, and this was in, on this person's dissertation. Is from this particular table, and that what they found was that actually it it actually affected the microbiome development in terms of the quality of the type of organisms are actually were higher and with bacteroids, which is one of the quote unquote good guys in terms of commensal organisms, and those animals that got lost.
OK so again earlier. So again, in this case, it's not just about growth, you know, directly speaking for the animals needs, but also in terms of what it could do for microbiome development as well. All right, the second thing I'm gonna talk to you real briefly is heat stress.
So heat stress, this is a study that we did at at my contract research organisation where we do vaccine studies, because we've always had a difficult time getting animals to, Respond to a, a BSB challenge. And so we did, so we had noted, in an earlier study that we had done that we really had a good response when the, the temperature was over 30, about 35 °C. And so what we did then is we went ahead.
And did this little study where we took calves, either loaded them up on a truck, and hauled them, not for a long period of time, about 3 hours, or we hauled them and then put them heat stress and heat stress was basically after we challenged them, putting them in in. A little tent that we made at 85 °F for for one hour and commingle with with other calves at the same time. And what we found from that consistently was that the winner was all we needed to do is put the heat stress on them.
We gave them heat stress. And we have lungs that look like this. We had just tremendous BRSV and so again, telling you again the importance of having a stressor like heat stress.
So a virus that normally BRSV doesn't cause a lot of disease, but you add a stressor like heat stress on it and you end up getting very severe disease. OK, the third thing I want to talk about then is, is the effect of vaccination and bovine respiratory disease. So one of the things again in in the US we use a lot of modified live BVD vaccines, and two of the predominant strains we use in the US are called Singer and NADL, that's the strain types.
This is a paper published back by Jim Roth at Iowa State back in the 1970s, and what he showed was that with either of these common vaccine strains that the ability of neutrophils to kill was inhibited for about 10 to 14 days. And the thing is that in young dairy calves, Or young calves in general, their neutrophils don't work that great to begin with. They actually have more of them.
But now, if you add on top of that, I vaccinated, it's going to, you know, you know, just make those, those neutrophils be less, that much less active in terms of being able to kill and that's a big deal. So what we made the recommendation then over the years, at least in dairy calves, is try to avoid giving these vaccines in the 1st 2 to 4 months of age because again, it allows that calf to his immune system to get. Needs to be.
Now, the interesting thing is that, and, and beef calves in the US because they're on the, nursing the cow, so they have their, their mama there and plenty of, of TLC tender loving care. So typically, then we, and young calves will talk about that are nursing yet, that, you know, at least give them a month of age before we do it. But again, the point there is to allow those animals again to, to be able to, to have a good homeostasis before we do that, put a stressor like in this case, BBD vaccine to have an effect on that.
We've also seen, you know, work in terms of delayed vaccination. I'll talk about that in just a moment, and then also gramme negative. So let's talk about delayed vaccination.
This is a little bit more sort of a I don't know, maybe controversial is not the right word, but you can certainly find studies that sort of go in both directions in terms of animals on arrival. But I would say in general we've, that we've seen that if you wait 14 days, so again allow these animals to have good intake in terms of feed and water, before you vaccinate by delaying it, so you can see in this study it didn't affect body weight gain or morbidity and high risk. Labs, administered vaccine on, on, day zero, so the ones that got initially, they had a little bit better, titers, and told what white blood count was greatest, when they were delayed.
OK. So again, I want, I don't, I don't wanna, particularly I know that for example, BBD is one of those viruses that actually can depress white blood cell count. So again, they did, they did better when they were delayed in terms of again the white blood cell counts as well.
And this is a bigger study that was done. By Del Miles and his group in Colorado, and they delayed vaccination with the viral component only 30 days, and there was no effect on morbidity. So again, all the calves, you know, they saw the same level of sickness, but it decreased the repulse.
So animals they had to retreat or decrease significantly in the animals that they delayed vaccination with with the modified live viral vaccines for 30 days. All right, the 3rd, the 4th point I want to talk about, 3rd point I want to talk about real quick and is then other things about vaccines. So we just talked about use of modified life.
Here's another issue we have, and that's a gramme negative. So endotoxin that's in gram-negative bacteria is, is very immunostimulatory. In fact, there's even some vaccines that carry a small part of that.
They use that as an adjuvant. But we need to be aware that when we're using gram-negative vaccines that we need to make sure that we don't use too many of them, and we talk, we use more than one, we call that stacking. And what I did, I've listed here, here in kind of in the order.
Of the amount of endotoxin that they have, and what you can see is that the, often the mastitis vaccines that we use for coliform mastitis probably are some of the most reactive, and then things like more axellobobus for pink eye and hisophy somus also can be very reactive. And then here's salmonella. I think to be Aware of this, particularly things like scar vaccines that are that are that are subunit.
They only contain say the finbra or the manhymia vaccines that only contain the leuotoxin. They're not gonna have those properties. The only things that are whole cell one again, what we try to do is try to avoid getting too many of these at the same time.
The other thing that that I want just to point out to you is that leptose spiral, although it's a gramme negative, does not contribute to endotoxin sacking. And then the reality is, is that, you know, sooner or later, you, you know, because of, of labour or an opportunity to work the animals, you're gonna have have to get multiple vaccines. If you have to do that, you need to use more than one and this you're one on one side of the neck and one on the other.
That's because all the action, when you give a vaccine, it really occurs in the drain lymph nodes. So if we can actually give the vaccine to draining lymph nodes, there's an advantage to that. And again, the, the, you know, the, the big thing that, you know, is, is this, as you said right from the start, is avoiding stress and whatever we can do to, to keep that from happening, you know, the better off that we're gonna be.
The last thing I wanna talk about then. With in this area in terms of, of vaccines and, and things to be aware of, and that is inflammation and body condition. So again, one of the things that we've learned from COVID is that again that, you know, people that were obese, had a tendency had a much bigger risk factor to develop disease.
And part of that is because with obesity. And so again, if we're looking at, you know, fat calves or, finishing animals or even transition cows that have fatty liver, they're gonna have more macrophages that are more reacting, one of those angry ones. So again, there's gonna be more increase in in terms of the ability to producing these pro-inflammatory cytokines.
And if you look at that, so you've got that going on, so you've got this more opportunity for inflammation, and then let's say you do things like, again, you're weaning a calf, you're changing the diet in, in a, in fat calorie, and changing the diet in transition cal, you change that diet, so there's a feed change, it could be, you know, restricted feed intake. And so what you end up then is you change that microbiome. So between this inflammatory meat eaters we have here and then the change in the microbiome, we can actually get an overgrowth of gramme negative back.
Bacteria, they can re-release their LPS and then we can have the LPS released that way. So not just from vaccines, but also from actually what's going on in the, in the, in the gut of the animal, when we have diet changes and again, those things together are gonna result in in more of an inflammatory response. And one of the things that we see in a, a lot of the feed yards in the US is what we call late dead.
So these are, are morbidity events that occur very late in the, in the feeding process, often involving . Issues of the respiratory and cardiac system that would again appear to be due to chronic inflammation. Like there are things that we don't see people that have heart disease.
And again, the idea that this adipose tissue, along with the the other changes that occur affect homeostasis, and now we see that, you know, inflammation and this is a, a diagram from, a presentation that you got. Grafts are put together, and just showing again this idea of, of, you know, this heart disease and then pulmonary hypertension, you know, resulting in that in terms of again, and if we think that that could be again related to what we're seeing in terms of certain genetic lines of animals in terms of a lot of marbling of having more issues with this kind of, of issues, you know, we need to be aware of that. And again, it's a, there does seem to be a, a genetic component to this, so there's a negative impact of production and carcass traits, and, and again, it's these macrophages again get back the idea that they're angry, and then they in turn produce more of these inflammatory cytokines.
It gives, leads to pulmonary hypertension and chronic, heart failure. All right, so we've talked then, you know, about these issues with the immune system. So what can we do to help modulate that?
And, and, in these last few slides and I wanna talk about that. And so, one of the things that we certainly are aware of is that we're trying to use less antimicrobials. And again, here what we've been talking about today really is about homeostasis and the importance of the microbiome.
So I really want to spend the, you know, the last few moments of this talk they were talking about some of these some of these products and what we understand. So first of all, you know, there's a wide variety of products out there, and, you know, you know, and just because, for example, they say it's a beta glucan, depending on the source, it makes a big difference. So, you know, beta glucan is in the beta glucan.
So you need to understand what's the research that might be done. And one of the problems we just don't have a lot of research and that's my second point here is we've been trying to figure out how they work and, and, and that's how do we Measure that, so I can tell you the mechanism and give you the idea that, you know, probably, you know, there's certain mixtures that we should use at certain times. And do we need them all the time, but, you know, probably at times of stress, and you could come back to me and say, when aren't they under stress under some of the things that you've talked about today, and that would be a fair argument.
So, this is slide that shows you the idea then that you can have, you know, many different contributors in terms of some of these probiotics or prebiotics. So what you see here, for example, is the production by certain types of filamentous bacteria. their products actually result in again, an amyloid that actually again helps in terms of regulating immune system.
Here you see the Congestion. So in this case, that'd be metabolite produced by breaking down fibres, so the short chain fatty acids that we talked about. And other metabolites that you see here again affecting the production of antimicrobial peptides.
And, and again, you can see again we turn, you know, like that regulatory cell, we've talked about this pathway at length, but again, these are all contribute to, you know, to different pathways that in the end, we're all gonna increase the regulatory, Aspect of the, of the, of the immune system at the same time enhancing the barrier. Another thing that's been used, are the use of, of non-glovine antibodies, and these have been, been often used orally. So there's another thing to sort of modulate that.
And again, they have some probably direct effect on pathogens, not gonna have very much effect on this regulatory effect that we just talked about. So, so, basically, they're gonna, you know, their presence is gonna be there as long as they're there, they may have some effect, but they're not gonna have the effect in terms of, of the, of that regulatory component that we probably see with other classes of prebiotics and probiotics. So, if we, you know, look at, you know, some of the fundamental management things that we need to be aware of when you're, you're gonna see the, the word dehydration here a few more times.
We know, as I just told you that dynamic barrier, consists of mucus, and cells have to be able to get there. And so dehydration is dramatically affected by that. Innate immune response, which includes things like the TNF, the pro-inflammatory cytokines, and neutrophils and other phagocytic cells.
Again, that's gonna be affected by, by dehydration. Again, that the cells can't get out there, but again, we mentioned the importance of eosinophils. So again, so Eosinophils, their presence is going to, Typically be a good effect in terms of being able to tell us that we've got a good anti-inflammatory response going on.
So really dehydration is about the barrier and the overall immune response. And then finally, again, the adaptive immune system is gonna be affected by dehydration too. So, again, if I can't leave you one other one message, just make sure that when it comes to water and water sourcing of our animals, the sooner the better and obviously the quality makes a big, big difference as well.
All right, so to summarise, and we've talked then about multiple stressors. So basically, physical, physiological, and environmental stresses, they all have a negative effect on the immune system. You talked about then avoid turning those those being bomb because they turn on pro-inflammatory responses and so things particularly like vaccination and surgery along with weaning and those kind of things are really going to have a, have a negative effect.
One thing that we didn't talk about, let just mentioned here is the use of non-steroidal anti-inflammatory drugs. They have had been used successfully, even as metaphylaxis, but the key with them in terms of helping us with this this inflammatory response is getting those in prior to the inflammatory events. So if there's a lot of stress going on and then you give it to them, it's probably too late.
So again, we need to You know, get that done early before that pro-inflammatory response occurs. And I think the future, you're gonna see more immunomodulators. So some of those things are prebiotics and probiotics, but you're gonna see some other modulators as well, that will come on the market.
I think that they're gonna help us in that regard. So again, so that, you know, the, the, the sort of the key takeaways here is really understanding that this microbiome and the importance of it as it interacts in terms of homeostasis. And now what we can do in terms of diet, dehydration, and intakes really is gonna have a big Effect on that.
So it comes again back to man we're talking about health. And again, to my last parting thought in terms of pre and probiotics is we're gonna see continued use of them because we're gonna see the decreased use of antimicrobials, but again, we need to understand how to use them and again think it will be in combinations and not by themselves. And with that, I thank you.