Hi. My name's Simon Daniels. I'm an associate of coin science.
Probably one of the few niche people, in the world who gets really quite excited about horse guts. A And that sort of comes into the health, the disease diet and is becoming more linked to, gut function and how that can also link into horse behaviour. So this webinar, is thinking about you are what you eat, the effect of diet on the guts on the brain and on horse function.
So what are we gonna do? What's the webinar plan? So the idea is to look at the role of the diet in gut health and in horse behaviour as a bit of a a start up overview.
Then think a little bit about the gut microbiome and its role in horse function. And we've seen a lot of studies over the last decade looking at the the gut microbiome and trying to really see what we've learned from those and where it's taken us. And then I'm gonna go on to think a bit about this idea of the gut brain link and and what do we know about the gut brain link in the horse.
How can we look at it? and And what's that telling us and then to try and bring this, in to be a little bit more practical at the end, actually, having a think about what might all this information that we've gained over the last 10 and and even beyond years, what would it all mean for horse management? On a practical level, how might it be useful?
So I want to start by thinking a little bit, about our suppose to what I would call traditional ways of feeding. And actually, it probably is only 20 years ago, but it doesn't feel that long ago that we were talking about cereals and in some ways where we discuss things about being heating and non heating, and we had these ideas or there were ideas that were truly out there where, oats, oats are heating. When When it comes to cereal.
But barley is non heating. And when you look at this from a nutritional and chemical perspective, it's nonsense because they're all packed with starch. In actual fact, oats has the the lowest energy level.
And it has, an easily to get to, starch from a a horse's small intestinal perspective. So it comes down to how the cereal is digested. It also comes down a little bit.
I i in how it's prepared. But they will all have a heating effect, depending on how well they digest it and how you prepare them for the horse. So, some of the, earlier work looking at this, So I've got here, some work from Rody can still from 2007, and this is just looking at the 10 common horse feeds.
And I've just picked 11 particular graph from this paper, and looking at the glycemic response, of these feeds. So along the bottom here, you've got ALF Alpha so that in this example, they've got one fibrous feed in here. And you feed it, or this is Pref feeding.
And then you feed and a after a while, you get a very, very slight, increase in blood glucose concentration. But it actually and then it drops back down to feeding level again. Whereas all of these cereals and we've got in here.
Oats, barley, corn or maize? Jockey oats. And then this This cob, which is AAA.
Well, it's sweet feed in American terms or a, or or a AAA mix. We probably think of it as, and the mix actually has the highest, glycemic response. But all of them show the same pattern.
You get glycemic response because there's plenty of starch in there and as that gets digested, and you get, the that high pink growth ischemic response And if you compare, to to fibre sources, fibre sources tend to stay pretty low and steady as you'd expect, because they don't have that at starch, and and a much lower sugar content in in that same respect Or that's releasable in the small intestine because it comes down to thinking about how the horse would actually access this. So we know that when we feed horses cereal, we can get a blood glucose response which might link to behaviour and also potentially has effects on health. But I mentioned that we also have thinking a little bit about we have to think a little bit about how it's prepared.
So some work here from Veronique Julian's group, from 2006, sort of taking a two proned approach here, actually looking at how cereals are prepared. So if we fed them whole, we crush them. We ground them or pelleted or in this here, it's got popped.
But also the amount. So at the bottom here, we've got the amount of starch in grammes per kilogramme of body weight of the animal, and then the starch digestibility. And what you can see is actually, it differs a little bit for all the different types of cereal.
So for our maize here, we we get really quite good digestion when it's been popped. It's actually OK when it's been crushed. This is at the, a lower concentration.
But what we do see is as you move over and the amount of starch increases, the overall digestibility starts to to decrease. Barley behaves slightly differently. And so with the the barley, we can see here that actually, rolling it, is pretty good.
And grinding. It really helps to be able to digest it. But again, if you go up in the amount fed per grammes of kilogramme of body weight per animal, then the digestive bee facility is not quite as good as it could be.
Oats. Actually, oats are really pretty good. And they're great pelleted.
They're great rolls, and and I mean, theoretically horses with good teeth should be OK, but what this paper then goes on to look at a little bit further is what doesn't get digested pre secretly. What is making it to the hind gut? And we know with the horse that the their ability to digest starch in the small intestine isn't great.
And they were They never evolved to eat a high starch diet. They evolved to eat a fibre based diet. So the fact that they don't have great pre sequel starch digestion shouldn't be a huge surprise.
But when horses are fed lots of starch, there is a greater risk of that, making it the hind gut. And and we are we are aware of the problems that causes, and we're gonna I want to think about that briefly in a bit. So what?
This study quite nicely shows is when you have low amounts of starch, then there's very little that is undigested. Whereas at the higher the amount of starch, it doesn't matter how you pretreat it before feeding. Then, it there's a good chance it's gonna make it to the high go because it's undigested pre.
And that's really important, because we know when we get starch in the hind gut, then it alters the bacterial community profile. It alters the microbiome. We increase the A melodic, bacteria.
We increase the amount of of lactate, and that starts to drop the PH. And we get a best case at slightly loose droppings at worst case potentially, a a colic. So, thinking about diet is really important, and I think horse owners and horse managers are much better at thinking about diet.
I think we've done a great job over the last 20 years at thinking about reducing starch. But I don't think people will fully look at how maybe the diet and starch links to into behaviour. And so I mean, one of my questions or one of my things here is Is it the type of stuff you feed or is it the quantity?
And this work here starts to suggest that quantity is a part of that. Now, moving forward. This, work from, Ingrid Verts Group in 2009 suggest, actually that Yes, definitely.
When we first used to think about safe levels of starch for feeding horses and then it it seemed at the time it was acceptable. And this is some work. From the states from from Potter's group from the nineties that you could feed up to four grammes of starch per kilogramme of body weight.
A A and that would be OK, but as you see, you get this huge blood glucose response. Whereas now we well, less than 1 1.5 grammes.
I mean, most of the one gramme of starch tends to be bounded around just the the ideal amount. But when you have a much smaller starch intake, then, you don't see that same, blood glucose response. And, it falls back down to a baseline level within 300 minutes of feeding.
So, we we have started to think about the way that we that we feed starch and horse owners and horse managers are coming around to this, and I think they're seeing the positive effects of feeding less starch. And I wanted before I even went on to think about starch and behaviour to just draw some starch related some conclusions. So where we have higher starch concentrations, we get a greater glycemic response, and that's fairly obvious.
And also higher starch concentrations means more starch getting into the hind gut. And and again, we're all aware that that is a problem with regards to changing the bacterial community profile and potentially leading to CIC, for example, but also the type of processing and the concentration will lead to that low glycemic response, and to less starch for the he. So there's there's two potential benefits here to a lower starch diet.
Especially, you know, our leisure animals really need very little starch. Our performance horses might need some starch, but if we can, for careful with the type and how it's processed one, we reduce the the risk of that starch dumping for want of a better term into the hind gut. But also, from that glycemic response, which may well or appears to have an effect on behaviour, especially at the the leisure horse end of the market.
So this idea of diet and reactivity, well, why why might diet and reactivity link together? And I suppose when I'm speaking to undergraduate students to sort of often simplify this a little bit to, a small child in a bag of Haribo, in in that all of that sugar other sweets are available, But all that sugar, can have that that buzzing effect. But why?
What is it about that that, sugar intake that leads to that behaviour? And there is a little bit of work here that looks into this. So how does starch and diet in the diet increase that reactivity?
Well, first of all, you get that, blood glucose spike. And with the blood glucose spike, you then get a spike in insulin and blood glucose that corresponds to serotonin, the happy gluon. So when you get that that increase in insulin to mop up the glucose in the blood, you then see aver thyro, which, leads to an increased up of tryptophan into the brain and precursor for serotonin means you end up with an increase in serotonin.
And that horse feels good. It may be excitable, and it starts to get quite reactive. And so it's not just a case of Oh, there's lots of energy.
So the horse is trying to burn off that energy. There is actually a pathway that allows that horse to feel good based upon that, quick release energy, which makes it brain, which then, has that behavioural effect. So this is probably our earliest or some of our earliest understanding of how diet can really link to behaviour and starts to bring in the the element of the brain with it.
But we've gone further, and we've tried to understand to a greater depth. OK, so what is this? What is this link?
How is diet, linked to horse behaviour? So this is some some more work from Veronique Julian's group. I'm from two years ago now, and they had a AAA group of horses, six horses that were initially maintained on 100% hay diet.
And over quite a short space of time, they changed their diet from 100% hay to hay and barley and they move it, in 10% increments. So they until they reached a point where the hay made up 7% of the diet and the barley made up 43% of the diet. So a high cereal, a high starch element to the diet, this group of horses, over in Dijon at this point in time had, can is fitted so they could actually get, direct hunger access.
And so they could do some microbiology and look at the the hunger ecosystem and what we found, from a a bacterial perspective is as it changed the diet, there was an increase in, amyloid and util and lactate utilising bacteria. And that's not surprising, because definitely on 43% barley, there's a, within their diet. They're going to be getting a good proportion of starch to the hind gut.
So therefore, the bacterial community in the hind gut needs to evolve because it's going to be fermenting starch. And it's gonna be producing lactate. And so hopefully you you you get a No.
Horses aren't particularly good at this you get some lactate util bacteria present that will mop up a little bit of that lactase so we don't go to acidosis quite so quickly. So the bacterial changes and and we see these types of bacterial changes when horses are fed starch. And there are lots of studies that show this from Veronique S earlier work to some of the newer, 16 sequencing approaches.
But in this study, they were also measuring behavioural change. So they were looking at social interaction. They capture a lot of video footage, of these horses and how they behaved.
And what's really quite interesting is they, on the highest starch diet. They changed their the way they behaved in a social setting. So they altered their behavioural interaction with other horses.
And their vigilance changed, and what they looked at them was Well, is there a relationship here between these behavioural changes and the bacterial changes within the hind gut environment? And they identified, yes, there was definitely it was a AAA positive correlation between the the way the horses were behaving and the changes in the gut microbiota. Now, scientists were probably a bit guilty of getting quite excited about relationships and correlation doesn't necessarily mean causation.
But it does suggest that there is something is happening here. If behaviour change at the same time that the dietary change is coming along, it's starting to suggest a link with the way they react, to, environments to people, their overall reactivity. And and could this be a sign of a of a gut brain link?
There's been more work since to to take this forward. So, Louise Bulmer, with AAA group at the University of Glasgow and N SI UC. And then they, took a similar idea, but it extended somewhat.
So they used a group of young, unhand, section a ponies. And they fed them a diet which was either high in starch or high in fibre. And they wanted to look at how the diet affected the well, the gut microbiome by proxy.
So they looked at the faecal microbiome. And they also looked at the behaviour and they looked at a a raft of behaviour measures. how how these animals behaved, to each with each other to a handler's reactivity to certain objects.
And there's, there's there's lots of data to to pull out of this study. But what I think is really interesting. And it was, the design of the study is, two diets and two periods.
So the animals that started on the high starch in the first period went to high fibre in the second period. So all all the animals had were on both of the diets. And what we've got plotted here, which is really interesting, are two elements.
So it's, the the this. We've got the bacterial community profile, of the two diets. And while there is some overlap and you can see in both, parts of the study, there's some overlap between the bacterial community profile.
The the the profile differs so that the hunger ecosystem appears to differ to diet. So you've got the high starch versus the high fibre, and I know there's maybe slightly more overlap here. We basically the same see the same thing twice, But what's plotted over the top, which is really interesting was that their sort of key behavioural finding.
And there's the the arrows and the the shape and the length of the line also links into the strength of the relationship. So the high fibre on the high fibre diet these ponies spent more time investigating their surroundings, whereas on the high starch diet they spent more time pace changing. And this happened both times, which again suggests that there is some link.
What that link is we don't really, truly fully know. But some link between how the gut microbiome evolves to diet and then an outward marker of behaviour. So they seem to spend more time investigating and being sort of exploring on the higher fibre diet.
Whereas I don't know if stress is the really the right word. But the pace change and the slightly more anxious approach was greater when they were fed the the higher starch diet. So this all of this starts to to sort of lead to a a lot more questions, I suppose.
But it's not just concentrate and starch that can alter or influence the the gut microbiome I think we have become. We became very focused initially. We we were already aware of, risk factors for colic associated with diet change, and we knew that high starch diets increased the the risk of colic.
And so we spent a long time, being quite excitable about Oh, well, we feed high starch and you get a different bacterial community profile. But actually, we also know that, even simple changes in forage can increase the risk factor for for colic. And so the fibre that a horse is fed will influence the bacterial community profile again.
It probably shouldn't be, hugely surprising. But there's a There's a few findings, a couple of findings here on, that I'm sort of thinking about linked directly to two studies. So this work from Christian Ding and Chris Pram and and others from 2012, was actually comparing, horses with colic versus, controls and horses fed starch and horses on a grass only diet.
And I'm just picking up on one little element in that, the horses on the grass based diet has, really small proportions of of velan, which are AAA group of bacteria that are lactate utilises, And when you compare when you think about velan in other species, So if we took cows for any or even humans. We have more cows. The ruin is probably a better example.
If you compare to a ruminant and cattle, they have a higher proportion of of a lacy, within the ruin. And so they can cope with a bit more lactate present because that lactate can be converted to propionate and it is made useful, whereas horses have a really small proportion of BA and and the grass based diet very, very few if the cereal, the diet tiny, little bit more. And so horses are not very good at converting the Lac tape from starch in the hind gut into propionate.
And so that sort of suggests. And I In a way, it feels like a partly an evolutionary link of what they're designed to run on fibre. And so therefore they're not good at converting starch.
And but also, if they're on a grass based diet, then they will actually have you know, very little microbiota that can actually make use of starch particularly easily. That's sort of one element. And the other element, the other element here is thinking this is some work from Shel Salem and others at Liverpool with with Debbie Archer and the group, And they looked at, a group of, horses that will feel kept for a year.
And they took repeated samples over the year and used those, to profile the bacterial community profile to see Well, what effect did different times of year? Different weather patterns have, on the bacterial community profile. And it did It changed and it and it fluctuated.
And I suppose with my sort of nutrition hat on, I would be thinking, Well, I'm not surprised to some extent that there is a difference between the spring and the winter, for example, because in the spring, if we think about the grass growth, we have, grass starting to grow again after the winter. It has the the grass itself of a plant has quite a low fibre content. The cell wall content, which contains the more structural fibre and the lignin, which is becomes the indigestible fraction.
The there's very little, which means within the cell there's more room for protein. There's more room for so called carbohydrates, so there's more of the solubles available, and so they would like a proportion that's likely to get to the hunger. And therefore unsuppress will slightly change that that profile, whereas in the winter in the winter the grass growth is very limited.
And grass that's been kept for winter grazing, depending on how it's been managed over the year. If it's been left to grow and get longer, then the likelihood is there's going to be a higher, indigestible fibre fraction. So you you're going to have slightly different microbiota that are going to be a that they're gonna be sort of optimised for trying to work through that more fibrous grazing.
And in the same way, differences with changes in growth patterns over the autumn. I mean it. It depends on whether you're thinking about grass that's just left for a whole season, or how many times it's grazed.
Cut. But I can see some plant associated links here, which would make it logical. Yeah, and I'm sure there are many other reasons that also link to why fluctuations in temperature have slightly differing effects on, the gut microbiome, and so we can see that maybe fluctuation is just perfectly normal.
And And I think when I think back, when Chris Brown was doing this work with Christian Dali back in in 2012, I was doing a PhD with Chris at the time, and I remember sitting in Chris's office, and we were He showed me some hot off the press data. And it was really interesting because back then we didn't have good databases. We didn't, know that much about the horse's gut microbiome.
And so there was all this whole raft of unknowns. All this all these unknown microbiota. And now, with time, we have better reference databases.
We have a much better idea of what we're looking at, but and here is the But, there's two elements here. The the the title of the slide actually comes from another paper from tax and others from 2015. That's looking at, It's a study focused on, beef cattle.
So it's looking at the ruin microbiome, But I'm going to apply it to Pippa Morrison's work here. Which these graphs come from, the players change, but the game remains the same, you know, very early on we got really keen about. Well, look, we've got all these different microbiota, that that make up the horse's gut microbiome.
And we seem to have this idea of a small core. Kirsty Kugel's PhD works that are focused on on the core, especially in the in the UK and horses in the UK with this small core microbiome. And then the rest of the microbiome of the of the horses, of the gut microbiome of the horse is much greater and made up with smaller fractions.
And that's great. But then we also got very keen about Well, if we do some sort of intervention and we look at the gut microbiome and we see a change, well, I is that change? Is that the reason the horse is colic?
And that was a sort of great and slightly wide sweeping comment because in actual fact, the players can change. But the game does sometimes appear to remain the same. So what?
We sort of turned this as is functional redundancy. And these two figures here, from Pepper study from 2018, suggests that she's got three groups of horses. And, there's a control group.
An, obese group and an aged group. And we've got an aged obese in here as well. and you can see that the, this denotes the sort of bacterial community profile, and the animal phenotype seems to slightly influence especially more so on this side.
The phenotype is, influenced by their their, the animal makeup. But, the output and this was this was using a metabol Loic approach. But looking at OK, what's the PH?
What's the propionate buta acetate and all the other branch short chain fatty acids. And in actual fact, while the bacterial community profile of these differing veno two types was different, the output in function was the same. And that's where this idea of functional redundancy comes in.
And so while the bacterial community, the microbiome might appear to change, the new microbes that are taking over the space might actually do exactly the same thing that the old ones did. And this is really where we have to be quite careful about thinking about just structure versus function, because for quite a long time, initially we got quite excited we had using amplicons sequencing for 16 S. We can, quite reasonably from a cost perspective, look at different interventions with horses and say, OK, so we have a baseline set of samples and then we make an intervention.
And if we get a change in the bacterial community profile, we'll then make the assumption that the change that we made led to that change in bacterial community profile, and that may well lead to an outcome. But that makes the assumption that all the microbiota are doing a different job and they're not always It may well be that OK, we change the profile, but message maintains the same, and that makes it a little bit more difficult. It's not saying that I'm not saying that 16 S sequencing amplicons sequencing isn't a useful.
It is a really useful tool. And there may well be times where we can get an idea of function from structure, and we're gonna come on to one of those in a few minutes. But actually, thinking about function is really useful.
And peppers used metabolisms in this study example I used here and we've done a few metabol studies they can be really useful to give you an idea of function, but it doesn't always perfectly T with structure. You can use a full shotgun sequencing approach, and and look at all the metabolic pathways that are in play. That is quite a good way to to give you an idea.
The problem with that is cost. I'm still looking at roughly about 1000 pounds a sample, so you your studies get quite expensive quite quickly. So there are lots of useful things we can get from prion sequencing studies.
I suppose my message is don't get too hooked up on structure, but try and think about structure and function. What I want to talk about next. I'm sure many of you saw in the press.
Very recently, I was, quite fortunate. I got asked to comment on this. The new scientist, this is some work that's come out of the University of Surrey.
It's Chris Pro's group. A friend of mine, Joy. Len is the the first author on this paper where they were looking at the microbiome of, Thord fs.
And they followed these fs over time. So they in the initial part of the study, was thinking about the early life and the early development. So how does the, the gut microbiome of a thoroughbred for all develop over time?
But they tracked them for long enough that they tracked them into racing, and so they were then looking at for how do early life events influence performance? In in a thy race horse. I've probably got this slightly backwards because I've got a, a AAA figure from their paper.
That's that's just out coming up in a slides time which looks at the how the the microbiome changes. But I want to focus to start with on, this idea of diversity. So from a lot of the microbiome studies that are out there, we've we've known for a long time We've had a really good idea for a long time that a more diverse microbiome is a good thing.
And when we think about, a lot of the from a lot of health, for example, then, the broader diversity generally the better, and we get this idea as well, I suppose, thinking that maybe if If, of course, it's quite a small core microbiome. And then the the rest of the microbiome is made up with with, more diverse species that are in fewer numbers, that the diversity potentially it is a good thing. And so what we have here this, study, looked at, diversity within the microbiome.
So we have, various measures of alpha diversity here, So this is within sample diversity, and these are doing different things, so I'm gonna pick. Shannon, for example, is a nice example of species richness. K.
One looks for, smaller species that are that may be lost or more rare within the the gut microbiome, but may still play an important role. you know, observed species is is looking at the the number of different species observed. So you've got these various measures of, of diversity within the microbiome.
So they looked at the diversity, but they also looked at this associated with health. And so what we have here are some specific health related events. So we've got respiratory events, gastrointestinal events, soft tissue events, and orthopaedic events.
And these are our sampling points or the sampling points in their study. So, you've got sort of, two days old up to 365 days. in And so we can see over time the, these measures of diversity and any with a with this is against a a hazard, ratio, associated with the event and and any with a AAA black line around the dot are, significa statistically significant.
And what we can see here is these horses with the respiratory event had lower diversity, and this was relatively early on within their journey. There's also especially where there's there's lower diversity. There is a, a A at different points.
There's some significant effect with soft tissue events and with orthopaedic events, but not with gastrointestinal. And so we looked at the these, effects looking at OK, well, if we take some different health states and we look at the, the diversity within the microbiome, and then looked at this from, OK, how if there's higher diversity actually looked at survival factor, Then there's a AAA positive effect here and and then it's traced through to to the sort of the cap in Myer plot of, of survival or less incidence of, disease. Again, what becomes really interesting is when you then start to consider the the diversity within the the microbiome, and their performance when these horses started racing.
So what we can see here is where we've got higher diversity. Then if we look at a horse's official rating there, there's a relationship. The higher the diversity, the higher the official rating, or the greater the the higher again, the higher levels of diversity.
They had greater earnings, the ones with higher diversity within the gut microbiome. Then you have greater placings. So we've always wondered, I have talked to people in the past about it.
I wonder if there's an effect of, microbiome performance, and this is a really, really clever way of doing it. It's a really, really nice study, and I think it's really put the idea of the importance of gut health on the map because people can see actually early life, and that's where this comes from. Is is really important.
The development of the microbiome and the the species richness and the that, diversity actually appears to be linked. And again, it's a correlation may not be perfect causation, but it seems pretty strong evidence to me that, this can have an outward effect on performance. And so, they've kind of tracked back as to Well, what might this be linked to what I've got on the left here, actually, is the the the early microbiome development.
So we've got the very early phase, and then going through the different time points, O of the study. So as these folds start to age, we see a a change in the pro in the sort of the, proportion is not the right word. The the community, the community evolves.
And that's not really surprising, because bowl two days of age is on a milk based diet. And so therefore, the the gut microbiome is going to be I it it comes through initially from the dam. It's going to be very much focused on on the food that's coming in.
As that hole starts to, investigate food starts to take in some fibre, then pack up, Microbiome will start to evolve and as they, are exposed to different feed elements We we saw from shale study, the the the Different seasons. You know, there's gonna be bits of fluctuation, but it will evolve and develop its own gut microbiome. Now we know from various studies in the past that certain interventions appear to have an effect on the bacterial community profile.
So there's been quite a bit of work in the past looking at the effect of antimicrobials. And it's not hugely surprising that antimicrobials influence the bacterial community profile O of the gut. And and various studies have shown that, when you give antimicrobials, it alters the gut microbiome and then over time it will start to try to recover.
And various groups have looked at other things. I looked, and several others, several other groups as well. We looked at the effect of, and people have looked at the effect of, protein P inhibitors and various things that we that we use various treatments for horses to see more.
Might this affect the gut microbiome? Antimicrobials is probably the the greatest, effect. But this is really interesting because this study looked at well, if these animals had antimicrobials in the first month of life for a warranted reason did that have any effect, on the outcomes of the study?
And what the data suggests is those that had antimicrobials, had reduced diversity and also had from a performance perspective, AAA lower EFI rating and, lower ranked earnings. So it would appear that from a management perspective, when horses are given or foals are given, antimicrobials in that first month of life that can have a knock on effect on performance. And I would expect that that that comes down to the the early sort of makeup of the gut microbiome, where it's just starting to, evolve and become the the sort of the the new norm and it and it would appear that N, or later on, as the Microbiome starts to develop, maybe it starts to become slightly more resilient.
But that very early time point is really important. And and there's so much to this study to to try and take in. But I think one of the things that is quite interesting is having just said structure doesn't necessarily equal function.
Clearly. Here, there it appears that there is a relationship between bacterial community structure and hormones is just one simple, element to, to this particular study. Now, when I sort of set up this this webinar I was thinking very much about the gut brain axis, A And so I want to go on to think a little bit more now about Well, what is this proposed link between the gut and the brain?
And this started really having thought about the the earlier work that I mentioned with horses. So the reactivity of we feed horses, a higher starch diet, and we see more reactivity. How does this link further?
How does the gut and the brain link We we we know with the highest starch diets that that more starch can lead to greater production of serotonin and the horse feels great. OK, but are there other mechanisms that link the the gut and the brain? And, I had a chat with a really interesting guy from, University of Oxford, who worked there?
A lot of rodent studies and and it's human focused work. Really trying to sort of understand, gut brain links in conditions such as schizophrenia. And his group, I've been doing various bits of rodent work and been looking at the effects of of prebiotics and probiotics on, behaviours.
And it's AAA really interesting concept that you you get the the diet right or you have these influences in the diet probiotics or probiotics. They theoretically then support the gut microbiome. And what they were seeing in these rodent studies were, the the difference in outward behaviours.
So where they returned them as psychotics. So prebiotics and probiotics were in diet. They had an effect on, the gut microbiome, which then led to a a gut hormone release, which sort of also released anti inflammatory cytokines.
And these could then travel up and cross the blood brain barrier. And they were seeing a positive effects in the behaviour of the rodents, whereas those not on the psychotics say you could see that they believe they were seeing more in the way of leaky gut syndrome, and you were seeing more pro inflammatory cytokines which were having, a greater stress response. Activating the, HP a axis.
Which again was sort of, habituating, the leaky gut. And the animals, from outward behaviour. Respect to were much withdrawal were much more withdrawn thinking, Well, that's very interesting.
If we think about the horse studies, the way their behaviours change on on high starch diets seems to be closer linked to this, either showing a more outward an outward stressor and in a way, in the rodents being less investigative and and quieter could be deemed a bit more of a stressor. And, Louise bummer's work went on further from the study. I, described earlier and discovered that they discovered that there were D two, dopamine receptors, neurotransmitter receptors, which are associated with starch in the diet in both the gut and the brain.
So you've got the potential for the receptor, in both in both areas. So can messages really go directly from the gut and the brain that are associated with the diet? And so there have been a few studies, but it's an area in the horse that where there has been, quite a little work.
One of the difficulties is Well, how do you know what's going on on the brain? Because without physically going in there, how do you know that you're having AAA brain related effect? And this is where we have been using spontaneous eye blink rate, as a noninvasive marker.
Now, a spontaneous eye blink rate, was initially used, in humans, as, a a marker of stress. And actually, the the early work in this and there was a lot of work conducted in primates. And the idea was, well, they could use, a dopamine agonist.
And they could, and they managed to show a clear relationship between you give a dopamine agonist and you see an increase in spontaneous eye blink rate. You give a blocker spontaneous eye blink, rate reduces, And so where we see an increase in dopamine, we see a change Generally, an increase in spontaneous eye blink rate. And one of my colleagues, Andrew Hemings, and and his, research group Seb McBride and Matt Parker.
They've done some work in this area and and, a few years ago, They had a Pete student, Kirsty Roberts. Who, was looking at the use of spontaneous eye blink rate. And they were working with, strongly, stereotypical at the time with cryptitis, for example.
And they could see this this increase in spontaneous eye blink rate and, various groups. And this was work from from that group from SEB from Aberystwyth, with Richard Mott. And they, were actually looking at OK, well, there's a relationship between, for example, here cortisol and spontaneously blink rate.
And there is so what we would deem traditional markers of stress that are slightly more difficult to to gauge. Correlate nicely to spontaneously blink rate. Which is makes spontaneous eye blink with a really useful tool.
Apart from the fact that I often have students hanging around for lots of time counting horses blinking in a in a very structured and controlled way, it's a nice, noninvasive way to try and, identify markers, in the brain that we may well be able to try and link up to the gut. So we've done a a couple of studies, over the last couple of years, to try and and link the the gut brain axis. So here's a snippet from, a study from one of my, postgraduate research students.
And we were looking at, the gut brain axis during a dietary and management change. So, we observed some horses. These were all polar ponies that had winter out.
They were coming in and they were coming back to work. And the owners had their plan. Or if they were going to bring them in on this day, they would start feeding them and they would start working them.
So we just observed this change. And our only input was we in? We split them into two groups, and we gave one group a symbiotic, which is a like a psychotic, a blend of prebiotics and probiotics.
And we gave one group a, placebo, and we followed these horses. So we took samples as on the day that they were coming in from grazing. We took samples, 24 hours after their management change, 48 hours after their management change, and a week after their management change.
And it deemed it very much as a management change because it was a change in diet. It was a change in the way they were managed. There were several factors at play.
Now there wasn't a huge amount of change, and the diet that they were placed on was introduced relatively gradually. And it was it was low starch. It was only one gramme of starch per kilogramme of bodyweight at maximum.
But what we saw is those, on the placebo had an increase in lactate within 48 hours of the management change. So the the two groups, are are start to become separated. I.
I have only left in this PC a plot for 48 hours, but before 48 hours, the groups were all just merged in together. They start to separate out of 48 hours, and then they merge back together again. But we see a couple on on here.
These both these peaks and the arrows, they are, peaks lactate. And the amount of lactate was quite small, but it enough to, to differ between the the groups. And then we actually plotted, the lactate concentration against their, spontaneous eye blink rate, and we then have this negative correlation.
So the higher, the the blink rate the the less lactate, the more lactate you get, the the the lower the spontaneous eye blink rate, which was quite interesting in itself. I suppose there are a few interesting elements to the outcome of this study. Actually, they didn't have much starch, but it was enough to show an effect in the gut after two days, which appears to be mitigated by feeding this symbiotic combination this pre and probiotic combination.
If the horses had high or spontaneous like blink rate, that suggests that actually, they had a little bit more starch reaching the brain as we discussed before. And it may well be that actually that, the the pre and probiotics before, the starch even reached the hind guts potential for starch and a bit of starch fermentation in the stomach. Actually, it made it much more available, and it could get up to the brain when we had higher blinks.
Whereas, we're taking faecal samples here where we have lower blink rate and morph faecal lactate. It's more likely that without the symbiotic that starch made it through to the hind guide in small proportions. And therefore we don't see the the the reactivity up in the brain.
So it's a very small link, but it's a starting point that can we relate. Spontaneous. I blink rate.
So it's a metabolic change. It looks like we might be able to We took a very similar approach on, another study. And, II I haven't given too much of this actually, because I'm in the process of of writing it up.
But we wanted to look at the effect of, probiotics on the gut brain axis, considering horse behaviour. So we had a AAA group of animals, a group of eight animals, and they were being fed a a fibre only diet or a very high fibre diet. With a little bit of high fibre concentrate which contained, various strains of probiotic sacro CC I and we wanted to see how this, this dose of yeast affected, digest ability.
But at the same time, we were monitoring behaviour, spontaneous, high blink rate and looking at the the faecal metabolism. And it was really interesting because we had different, concentrations of yeast. So we had no yeast, low, medium and high yeast.
And collectively the yeast didn't have much effect on fibre digestion on the group as a whole. Nor did it have much effect on the the faecal metabolism. But we because we were monitoring the behaviours, we managed to we Well, we we characterised based upon the the personality, the behaviours that we recorded for these this group of animals that they that half of them were much more dominant and half of them were much more subordinate.
And when we looked at the data for these two behavioural phenotypes, we saw differences in their ability to suggest fibre based upon their their phenotype there was improved by digestion in our in the subordinate phenotype. And the behavioural phenotype definitely influenced the, spontaneous like blink rate and its interaction with the the yeast in the diet. And again for the metabolism, the faecal metabolism, we saw differences in the faecal metabolism based upon the, the behavioural phenotype.
And there again, a negative correlation similar to the previous study between blink rates and different metabolite concentrations which the metabolites we identified in this study were precursors for dopamine, for example, or things that were linked to, rated passage in the gut. So there are some really interesting gut brain links that are starting to emerge. The difficulty starts to become, But what is driving?
What is it you know is the gut driving the brain is the brain driving the gut? How might behaviour have an effect? Because up until now and we've always thought, Well, maybe behaviour is influenced by diet, but maybe diet.
Maybe behaviour also influences the, sorry. Maybe animal type influences the outward behaviour based upon the diet, so it just starts to become more and more complicated. So I thought before thinking about the practical application, we'd look at some conclusions of the the material that I've presented today.
So diet definitely appears to influence the gut microbiome structure and maybe the function, at at that we don't really, know enough about, but definitely, it it looks like there's potential there, and and we can try and continue measuring function and see if we can look at this relationship between structure and function diet appears to influence behaviour from a very simple, we have a high starch content in the diet, and therefore the animal is more reactive. And that may well be linked to the gut Microbiome, and and maybe part of that reactivity it is linked, to the, metabolites produced in the gut management influences, gut microbiome and horse function. And the work from Chris Brown's group, I think really is is a nice piece, you know, in that jigsaw puzzle, and the way that we manage horses can influence, the gut microbiome can influence their future performance.
And so on. And so a lot of the old rules of feeding of make changes. Gradually, these things you sort of look at and think, Well, there really is some sense behind Why those why those things were sort of put into play.
And maybe the innate behavioural phenotype that we've seen in some of our recent gut brain axis studies might also influence the gut in the brain. So the way that the animal behaves normally might influence how it reacts to certain diets, supplements, and situations. So I left my little black book.
I've got my little black box image on the screen because that's how I like to think of the horse's hind gut. Very early on, we used to think, OK, we put food in, something happens in the middle and we energy and faeces at the other end. And then it starts to become when we put food in.
And there's this diverse microbiome and we get faeces, energy and various metabolites out. But the further we go and the more of the surface we scratch, I think the more we realise that actually, we know very little about the horse's gut microbiome. I think it's gonna keep me busy for the rest of my career.
That's, that's for sure, trying to unpeel those layers and try to get a deeper understanding. But maybe that this this black box actually has a much bigger role in health and body function than we've ever really given it, credit for in the past. And so of this of these things that I've talked about, on this webinar what does this mean for horse management?
And how could we practically use this information for to help support, horse managers and horse owners in the way that they should be managing animals. Well, I think it's more evidence to carefully consider the horse's diet. You know, I think we I like to hope that we're moving past the point of, where that we were at 20 odd years ago, where horses were very reactive and the easy approach to from a horse owner, especially on the leisure market side of things, would be Well, let's look at using a karma.
But actually, maybe the problem isn't that the horse is reactive. It's that the diet is wrong. It's the starch content is too high.
So careful consideration to diet. It is important. Some horses are naturally reactive.
That's fine. But are is it is it the natural reactive? Or is the reactivity linked to our our intervention and management?
And in which case, that could be the the diet. So careful consideration to the diet, and really thinking again about each animal as an individual, ideally keeping all changes in the diet or all elements. Gradual.
I don't think we know enough about the structure function link to be able to make any great Presumptions. But if changes in the diet lead to changes in the microbiome and there are there's potential that also links to function, then it is still good practise where possible to make the changes gradually. All the data suggests it's really important when it comes to starch in the diet.
There is some data with regards to fibre in the diet area, and a few groups, including our own, are are trying to do some more work. But it seems sensible and logical to try and recommend that all changes of diet should be gradual. But just because you get changes in bacterial community profile and you're looking at studies that doesn't always necessarily infer changes to function, it might, diversity in the microbiome is really important.
That work from Chris Harman's group really nicely shows how important it is to allow the early stages of the gut microbiome to develop, because that may well link to, performance and also health parameters. You know, the broader the microbiome diversity, the lower the risk. In that case of, respiratory illness.
A as as an example as well as the the other conditions that they looked at. So if we can encourage the development, and that again is a management practise OO of, of these young horses to develop a healthy microbiome, I think that's really important. And then innate behavioural phenotypes, appear to have some kind of influence.
So in the the outline of the study that I presented from a fairly recent work suggests that, in one group, we saw a a dietary effect of a probiotic that we didn't see in another. And when we look at studies, there are varying studies with regards to probiotic use in horses. And some studies say, Yep, that had an effect or it increased fibre, Digestibility and other studies says No, it it didn't.
And the really difficult thing when you start to try and pick some of these studies is well, depending on the probiotic, it's gonna be, if it's if it's EU registered, it's gonna be a sacro Cervi strain. But there are different strains, and they're fed at different rates. So it might be that different strains at different feeding rates have an effect.
But it's also just possible that the behavioural phenotype, as we saw in our group, has an effect. And so if you had, if you didn't know about this, you may. Well, your study findings may well be diluted out by, more dominant animals in the group where, the there seems to be less effect.
So there are some practical things that can be taken from all of these, microbiome studies. But But what is what came first? The chicken or the egg and what's driving?
What the gut drive, the brain or the brain drive the gut. I think it'll be a while before we get there, but I think we're starting to realise that actually, the horse's hind guts not just a black box, it's actually an important organ that seems to have, a a connection to health and behaviour is just two examples, in in the normal horse. And I hope you found that interesting.
There are some references. They're probably a little bit small for you to read, but I hope you enjoy the webinar
