Hi, my name's Jamie Pratton, and today I'm gonna be talking about the assessment of poor performance and training utilising laboratory samples. So through the lecture today, I'm going to do a few things. Firstly, we're going to talk about the interpretation of some of the laboratory results that might be available to you.
We're going to look specifically at haematology, the leukogram, biochemistry, and then we're also going to talk a lot about lactate, and also just a couple of supplements that have been recently talked about in the, in the literature. So this is a massively simplified overview of what causes poor performance in the horse, but I think it is integral to understanding how we can move forward and how we can further analyse these cases. So first of all, we're starting with some oxygen, and we've got to get that from outside the horse into the horse.
And so the lungs, both the upper and lower airways are very significant in this and can be a massive port of call for your poor performance. Obviously we're then going to move that oxygen from the lungs, from the air around the body. So we've got to be considering our cardiovascular disease, whether it's within the heart or whether it's within the vessels themselves, as well as considering something like anaemia.
Next is the muscles themselves. So are there myopathies, or is there orthopaedic disease, not something we're gonna be covering at all today. And all of those things can contribute and lead to poor performance in any of our horses.
Now obviously, I have a picture of a racehorse here, but it doesn't really matter what horse it is if the owner feels that there has been a dramatic drop in the performance of that horse. But there are a couple of other things that can cause poor performance in horses, so we must also consider things like gastric ulcers. We know that that has one of the highest impacts of VO2 max in horses.
So if you're ever worried, always scope that horse as well. And then things like liver disease, which we'll come on to in a little bit. But when we consider testing bloods in horses, there has to be some rules for this.
Now the one thing to remember is that not all labs are made equal. And this sort of little sign on the side makes the mark or makes the point really that you can choose certain things. Do you want it to be good and fast, then it's not gonna be cheap.
So sending it to the likes of us, we will get you excellent results because we are very consistent with our testing of the laboratory. Whereas some of the bench top analyzers will give you spurious results, may not even tell you when those results are too high to read. But considering the actual blood tests, the likelihood of a false positive result, so in other words, a result that isn't actually truly abnormal will increase when you do multiple tests.
So in other words, if you do the same test multiple times, speculative testing. So are you just saying, OK, I'm going to try testing for everything. So in the ideal situation, your blood tests are going to be purely dictated by what you see in front of you, not what you think that it might be.
The problem is that in poor performance cases, you often don't have a very good clinical symptom and so you're dealing with a very nebulous disease. And as such, you are going to be considering speculative testing. The one thing to do is to consider what those results really mean.
Also, it might be that these subclinical diseases only emerge during written exercise or post intense exercise. So it's worth considering when you take those blood samples in relation to levels of exercise and rest. So what I'm saying is be sensible with your blood testing, but in some cases you're definitely gonna have to cast that net wide to get yourself some results that you can start working on.
And as I mentioned, remember which lab or machine you're using and particularly consider what your reference ranges are. Not all labs will have the same reference range, so make sure you interpret your results in line with that laboratory's reference ranges. And frankly some of them are really questionable.
So if you look at, say, proteins on some machines, you may see that the reference range is down at 21 for an albumin, that would be a severely hypoalbuinemic course. So have some common sense, look at it and question those results as well. But first of all, we've got to sort of consider what is normal and what is abnormal in these cases.
So, the results that we get for an enzyme, let's say enzyme X. We produce, we produce, sorry, at the laboratory, a bell-shaped curve to say, OK, where is our median result? And what we do is we take every sample for an annual health check in a horse with no clinical symptoms, and we say the median result is 10.
But how do we decide what the reference interpo is going to be for those horses? We take a standard deviation of about sorry, either side, and that gives us a reference range from 8 to 12, but actually in most cases we push it out to the 95th percentile, which is going to take it up all the way up to 14. Now, it's important to state in this one that there are still some horses sitting outside the normal reference range who are normal and vice versa.
So if we think about what it actually means, don't overinterpret the occasional abnormal result if it does not fit with the clinical signs. And that's because one in 20 horses will lie outside the reference interval. On the other hand, you can take a more liberal approach and say that only 1 in 40 will sit above or below the reference value when they are not abnorm when they are normal, so sorry, and therefore any abnormal results should be interpreted with care.
I think the really important thing to say with this is that always interpret those results in line with the clinical presentation, not in isolation. In other words, treat the horse, not the piece of paper. We see enough changes in blood results coming through the laboratory that are deemed insignificant er in the majority of cases.
So if we look at case one in this, this sort of example of a of an SDH of 15. You've got about a probability of 2.5% of those horses who present with that number being normal, 1 in 40.
Whereas case 2 is a 13, actually, you kind of talk the other way, and 1 in 6 of those could be abnormal. So it's important to say, just because it's within the reference range, if you say that horse is really showing symptoms of muscle disease, it may be actually that their level is slightly, their normal is slightly low. But when doing our laboratory analysis, it's really important to consider your differential list.
In other words, try and find a localising sign that's going to drive you towards the most appropriate differ laboratory test. Are we talking about an inflammatory disease? Is it an infectious challenge, parasitism, a respiratory inflammatory disease, although remember that unless it's pneumonia, there will be no changes on your blood work.
So although inflammatory within the lungs is not inflammatory within the blood. Or something such as a cardiomyopathy. Or is there something subclinical going on, or low grade disease, gastrointestinal disease, inflammatory bowel disease, gastric ulcers as I mentioned earlier.
Is there a hepatopathy or a myopathy? And could there just be electrolyte disturbances that are leading to the the exercise disturbances as well? And obviously, there are lots of things that we're not going to find on blood results.
In other words, just always look. Now this is obviously an extreme picture of a fracture, but we're not going to find orthopaedic disease on blood work. You know, you might find some small elevations in AP or something along those lines if there's severe disease, but it's not going to happen.
Respiratory disease, as I said, is not going to show up on your blood work in the vast majority of cases. And also some cardiac diseases won't either. So cardiac troponin, which I'll come on to in a little bit, will only elevate in cardiomyopathy.
It won't elevate in a lot of other diseases. So, actually you have to listen to that heart, you have to consider an ECG. So what subclinical disease affects performance?
This group, run by Richard, er Eric Richard assessed well performing clinical horses versus horses with average and poor performance. And what they found, unsurprisingly, is that the clinically healthy horses had very few diseases going on, whereas the average and poor performance had an increased frequency of subclinical disease. Now that sounds probably very simple, but actually it really highlights that these horses do have things that we have to go hunting for and it's not as simple as always being, say, orthopaedic disease.
And this graph shows sort of where they, they found, and what they found was that upper respiratory tract, particularly inflammatory airway disease, lower airway disease, were the big indicators of poor performance. Whereas actually locomotive diseases on the far right hand side of that that graph, really didn't attribute, it wasn't attributed to too many of those horses. So although often the first port of call, it might actually be better to start considering some more of the medical cases.
And what about specifically in the respiratory tract? What they found was that these poor performers definitely had an increased neutrophilia. So in the tracheal wash in the first graph I'm presenting to you, we can see that, sorry, that's the bronchialveolar lavage .
We can see that the normal, the red line cutting across should be 5%, and in both the poor performers, which is the light grey and the sorry, the intermediate performance in light grey, poor performers in dark grey, we can see that there is an abnormality going up sort of 10%, which is statistically significant. We see a drop in the macrophages which is consistent with the change to neutrophils as well. And then when we look at tracheal washes, we've got the same, so the, the line across should be sort of 20 to 25% in this study they classify it normal as 20%.
And again, we're seeing that the intermediate and poor performers have a significantly, statistically significant elevation in, neutrophils. Now those values aren't massive. We have to admit that a 10% neutrophilia in your BEL, a 30% neutrophilia in your tracheal wash are not dramatic, but they are indicative of disease and you're in the early stages, so well worth trying to fight and treat.
And what about in this group, still talking about the same study, were there any changes in our white blood cells and our red blood cells? And straight away, what we see is, so, group one is your normal, group two is your intermediate and group 2B is your poor performance. And these are rest versus straight after exercise after lots of training.
And we can see that these horses are consistently having lower hematocrits compared to the, the good horses, with a lower mean cell volume, mean cell haemoglobin, all things that are gonna affect your performance. But also significantly, lots of them had a markedly elevated inflammatory picture. So we got a serum amyloid A that was dramatically higher in the intermediate performance and also ongoing elevations in fibrinogen.
And both of those things say, OK, something else is going on, we really need to be looking, so we're just getting a hint that something's out there, we need to start digging. What about looking specifically at our red cell values? So how are we going to interpret these a little bit further?
I think it's important that That when you look at red cell values, if you have a marked hema concentration or marked increase in your red cell values, you've got to consider that polycythemia could just be splenic contraction and stress. So when considering splenic contraction, there's only about a 32nd delay from the splenic contraction to the increase in the polycythemia. So you've got very little time to take a sample before it will be affected by stress in that horse.
Remember, it will not only it will increase not only your red cells but also your lymphocytes, and it also takes about 2 to 6 hours for that to normalise once the stress factor has been removed. So any polycythemia question as to whether or not it is real. Obviously it could be associated with dehydration and if you clinically are suspicious of that, then you would compare it with your proteins as well.
What about anaemia? So anaemia can obviously be a very significant cause of poor performance, but it doesn't happen too often in horses, thankfully. We do see it in chronic inflammatory diseases, obviously blood loss and some of the more significant diseases.
And if you do find it, we have to take it seriously. If anaemic though, well, how does that affect your poor performance? What we're going to see is that it will lead to a decreased oxygen carrying capacity, and I know everyone understands that, but let's take it a little bit further.
So the CAO2 is your total oxygen content in your blood. And that's made up of not only your haemoglobin concentration, but also your SAO2, which is the oxygen the percentage of oxygen binding sites in haemoglobin that are occupied, and the partial pressure of oxygen to dissolve in plasma. And what we know is that haemoglobin is absolutely essential as very little oxygen is transferred into the blood.
So that total consumption total oxygen content in blood is your haemoglobin times your saturation times 1.34. So that's your big number.
Whereas your partial pressure in plasma is tiny, so it's only 0.003 times the partial pressure. So if you have a reduction in haemoglobin, you have a massive reduction in your oxygen carrying capacity.
Platelets, again, not gonna be particularly involved in actually poor performance, but a thrombocytosis rather than thrombocytopenia will be associated with inflammation. So it's just giving you that a little highlight to say, OK, let's look a little bit more. One important thing to consider though is that in the normal course, there is a significant diurnal variation in blood values.
In other words, we're going to see changes throughout the day in a number of blood values, meaning that some results can look quite spurious. If we look at PCB alone, and this was through the day, from midnight, and to midnight the next day, we can see that the PCB in these horses, this was average in a group of racehorses, varied between just below 40 all the way up to 50. And that has a significant impact on whether or not you feel confident this horse is anaemic versus polycythemic.
And this was just normal horses under no stress, under no exercise. We also see a significant change in your serum proteins. And this sort of is slightly lagging behind your your PCB.
But we're dropping from an average of 70, I think it was 72, down to sort of about 56, in the early parts, sorry, and then all the way up to 85 grammes per litre. So you're talking about a 30, nearly 30 grammes per litre change. Now I think in many cases we don't see quite such an a change in a lot of our patients, but it's something worth considering is if you find something that doesn't fit, then retest.
And how about creatinine kinase, so looking at your muscle enzymes. Now these aren't significant changes, you're talking about 115 to 140. Now that's well within reference range, but again, there is this constant change in your muscle enzymes.
But what can we do about red cells within training? As there have been a few studies looking at this one, this one was from the 80s, and we did over 12 weeks, and we can see that there is significant change in the amount of red blood cells present within the within the blood over that training period. So it's going from 8 to nearly 8.75 over a 12 week period, which you would expect with increased production of erythro or eating, and an increased haemoglobin concentration required for exercise.
But in about 1999, another group, Magawa Natal, looked at this again, and they found that exact same increase going up to 1216 weeks. But actually what they started to see during that training was that they started to plateau off, and you start to see a decrease in it again, up to 32 weeks. So actually in some of those more chronically exercised horses, you may see a gradual decline in your haemoglobin, that's completely to be expected.
And I know that's significant in racehorses where they are taking regular hemoglobins and they're really watching the red cell values and the haemoglobin values. So, do be aware and you can always tell trainers that you expect a slight decline if you're sort of talking 16 weeks beyond the initiation of training. And what about leukocytes?
So, abnormalities can act as a marker of inflammation and require further investigation, but stress alone will induce changes in the white cell count, and that's most frequently characterised by neutrophilia as well as a lymphoenia, so a stress leugram, and occasionally a year in ailia. If we're talking about that, if we are considering that this horse may just be stressed, so we've got neutral lympheenia and no signs of disease, no pyrexia or anything like that, it's always important to rule out an inflammatory process. So running a concurrent serum amyloid A and or iron and looking at your globulins will really sort of untangle that.
So if you've got normal serum amyloid A, normal iron, and, a normal globulin, but those abnormalities, then we can be pretty certain that that's just a stress lethogram. But when we look at each one, what does it mean? A neutrophilia in itself can be inflammation or stress.
So as I said, we need to differentiate with this acute phase markers. A neutropenia can be an early infection or inflammation. So in these cases we know that horses have a very small pool of neutrophils and therefore you can have a neutropenia very early in infection and inflammation, and then it will rebound into a neutrophilia.
How about a viral challenge, we normally expect a lymphocytosis. Although again in that early stage, we may see a lympopenia. And again, we relate back to that lymphoenia being associated with stress as well, so using your your serum amyloid A and globulins to assess it.
Whilst monocytosis can be a chronic inflammation and ears in aphilia, allergies or inflammation. I do struggle with ears in affilia in the mild levels of earsinophilia, because we so so rarely see such an allergic response in horses that you are getting earsinophilia. You can also have some slightly odd diseases like Meads, multi-epitheliotropic ear xenophilic disease syndrome, which can cause severe poor performance, but more likely it's gonna present with skin diseases, so, and liver disease if you have a dramatically high ear xenophilia.
But what's happening to our white cells during a viral challenge, and the reason I sort of highlight this is to marker is to say that what we can have really varies. So we always say with a viral challenge you're gonna get a lymphocytosis, and quite often may get a neutropenia. But actually, in those early stages of a viral challenge, you actually see a marked neutrophilia to start with at day one, and then a reduction to neutropenia by about day 4.
Whereas your lymphocytosis can take about 5 days to become significant. And that's all just to do with the amount of time it takes the bone marrow to kick into place to start creating more of the white blood cells and fulfilling the body's requirements. So just be aware that although you may be thinking it's bacterial or viral, it may be that you just pick it at the wrong moment in the the challenge.
But what's happening to our white blood cells in training? So again, these changes aren't dramatically significant, we're sort of sitting within reference range, but sometimes it might be significant when you are monitoring these sorry, these hematologies week in week out for the trainer. You're gonna see an increase in your, your neutrophils, sorry, and that's, that is a significant statistically significant increase in your neutrophils, but then it'll plateau out after about 8 weeks.
And your lymphocytes will slowly drop off sort of from about 8 weeks down to about 32 weeks. So these changes, as I say, are mild and probably not significant for your interpretation. But can neutropenia specifically be associated with poor performance?
What we know is that we see some horses that are presented to us that are bright, eating, happy in the stable, but whenever they are exercised, they start to rapidly run out of er of of of energy. And over several months this will keep recurring but will suddenly spontaneously resolve. And remember these horses are genuinely presenting in the stable as a normal horse.
And what we find is that these results, these horses when we take a haematology, have a persistently very marked neutropenia, so less than 2.5. And there's no acute phase response, so it doesn't seem like we're in an early inflammatory process, that's consumed all of those neutrophils.
When people have taken bone marrow biopsies to look at them, they're unrewarding. They don't tell us that there's a problem with the bone marrow. These are normally fit young healthy horses, so we'll be very unlikely to have bone marrow neoplasia.
The thing is, we don't know what causes it. Is it a chronic viral challenge, it's just low enough grade that it's not causing inflammation, but it's affecting production of white cells? Is there bone marrow suppression from some other source?
But it is significant because it does genuinely affect performance in these resources. But also it does seem to resolve spontaneously with no medical intervention required. What about our serum proteins?
So looking in general, albumin, is, is a big marker that we need to be considering. So obviously it may be high in dehydration, links with your polycythemia that we were talking about earlier. But low is more significant and we should be wondering about those in every single case.
As I mentioned earlier, be aware that not all reference ranges are made equal, and so be sensible when you're running a benchtop analyzer to make sure that your reference range that you're working on fits with those in other books. Obviously, little changes are completely acceptable. But a hypoalbinemia is likely associated with the GI disease, whether it's parasitism, IBD or non-steroidals if these horses are on a lot of non-steroidals, it can be associated with more sort of concerning things such as renal disease and threat facing.
In some situations though, you might be seeing low hypoalbuinemia associated with chronic inflammation. And that's normally because the body is pushing production into globulins and away from albumins. So if you've got a hypoglobular anaemia and a hypoalbinemia, you've gotta be considering chronic inflammation rather than maybe a true protein losing enteropathy or nephropathy.
Globulins are driven up during obviously inflammation, any infection, but also in liver disease. So if you're seeing a hypoglobular anaemia on an inflammed profile, but nothing else on there that makes you think of inflammation, get some more blood work run, get a liver profile run and see if that's what's driving it. And low is often seen, especially in those high intensity exercising courses, the racehorses.
But the exact aetiology of why they are hypo globular anaemic is pretty much unknown and generally seems to have very little effect on the horses, actually it has no correlation with performance, so generally you can be fairly happy that you can ignore it. And what about our positive acute phase proteins? So these we sort of mentioned a little bit, serum amyloid A, fibrinogen, iron, which one are we going to choose?
And remember that, sorry, the positives are your serum amyloid A, your fibrinogen, so they're gonna go up in inflammation, whereas your negative acute phase pregnancy, your albumin, which I talked about a moment ago, and you'reine. All of these will go up in bacterial infections and viruses, but also you can see these changes, you can see the, the changes you expect, positive or negative, in parasitism, neoplasia due to a release of interleukins, tissue damage such as myopathy, even dental disease, and sometimes immune-mediated disease as well. So it's not a, they are not clear cut as to giving you a diagnosis.
But what about each individual one? Why are they, why are we working on 3 different ones? For a long time, serum amyloid A has been our first choice acute phase protein to be leaning towards in the equ1 industry.
There are others that humans and small animals use, but they are generally not used in in horses. The reason it's been our first choice is that it responds very quickly and also it responds quite significantly and the trend can be monitored. Whereas iron is going to have a decrease and again responds quite quickly, but also has a slightly longer half life and gives you an indication about synchronicity.
Whereas fibrinogen takes a much longer time, so if we look at serum amyloid day, we're gonna see a significant increase after about 8 hours, iron about 16 hours, and fibrinogen after 24 hours. What I would say with most acute face proteins is that actually today, whether or not it's that significant, you know, as a one-off marker is, they're not always that helpful. What they're really useful for is a trend.
Are they improving with what you're doing? Are they getting worse with training, etc. Changes in environment?
Because if they are, then we need to be thinking about what is going on and how we're going to change that environment or the, the treatment. Muscle enzymes are obviously a significant part of our investigation within a horse for performance. A one-off muscle enzyme at rest is of limited use unless it gives you a clear cut answer that is massively positive.
But therefore what we need to be considering is doing an exercising post exercise CKAST. The easiest way to do this is to undertake a level of exercise, so sorry, take a pre-exercise CKST so we have our baseline, do exercise at a near maximal level. Now you should interpret this in line with what that horse is doing.
So, you know, a lot of horses that come through here aren't going to be able to do half an hour of trot or counter or whatever. Whereas if you're talking about a racehorse, you're going to need to get them onto the gallops and actually work them to get them to that maximal level. Then wait for 4 to 6 hours to take your sample, and the reason for that is that the CEK peak is reached at about 6 hours, and the AST at about 2448.
So if you're really in detail, I'd recommend you take one at 4 to 6 and one at 24 hours post exercise. And we should by then be seeing the drop in the CK, so we've had a one-off insult and then the AST increasing as well. What do we do with that information though?
OK, so we've got a myopathy, we've found that out. How are we going to start investigating it? Number one generally is looking for PSSM, polysaccharide storage myopathy.
Now in a lot of breeds it may not be significant, but PSSM type one is very much out there. And the easiest way with PSSM type one is to take blood or a hair root for genetic testing. We know that it is consistent and we know that it is an appropriate way to diagnose PSSM type one is by either of those methods.
Obviously a muscle biopsy will also work, so don't, don't put that out of your mind. But if we are considering PSSM as an differential diagnosis, we've got our myopathy, we get a negative PSSM type 1, then we can still consider a muscle biopsy. And this is the only way to test for PSSM type 2.
I'm sure lots of you have read about different genetic tests that are available, and they are out there, but there is absolutely no scientific evidence that they work. So don't use those as a primary way of testing because it's not going to be consistent. If you go and take a muscle biopsy, make sure that the lab you're sending it to is aware it's coming, so the RBC do a fantastic little crib sheet on how to do it, the different samples required and the speed with which you need to deliver it to them.
And you're going to, for what we're talking about, poor performance, you want to be taking muscle biopsies, of your, say, semitendiosis or semi-membranosis. If we're talking more about, sort of a more neurologic diseases, we might be taking the postural muscles, but that's not significant for what we're taking. If then we find abnormalities consistent with PSSM, then we've got to consider where we go.
We're gonna be looking at changing our diet, changing our lifestyle, making sure these are gradually exercised. And there's some really good resources, sort of, Michigan University, thanks to Steph Balberg, have some great pages on the internet looking at all of it that you can send the owners to and you can really, alter their diets and monitor them closely. What about liver enzymes though?
Obviously, liver, if it is a significant disease, so if we have true hepatic encephalopathy, then we are going to be talking about something that is significant and will be causing poor performance. But the chances are that at that stage, you're already aware that that horse is quite significantly sick and we're going to be looking for that disease. But what about exercise?
Does exercise actually induce a liver disease? What we see is that during training from day one all the way to day 32 in horses that are trained hard, we see a consistently elevating GGT. And that you start to get into that level where actually you do have a hepatopathy in inverted commas.
The control in this study was actually a group of horses that were moderately exercised as they should, but you're still getting that increase up towards an abnormal GTT. But why does it occur? And the answer is that we don't really know what's causing that elevation in GGT.
There's postulation as to whether it's hepatic hypoxia or ischemia associated with exercise, you know, if these overtrained horses genuinely are having prolonged periods of hypoxemia. Or is it that there's GI hypoxemia specifically associated with, change of the, the blood flow during exercise? Or is it that there's actually physical trauma from the colon?
We know in colic, for example, when there's a displacement, that that causes an increase in GGT. So does the movement of the colon of the GI content during exercise actually lead to a GGT elevation? But does it cause poor performance?
These, these sort of levels that I'm talking about, it doesn't seem to, you know, these horses aren't significantly poorer performing when they have an elevated GGT. So if you're sitting in the 50s, 60s, as per our reference range, then maybe you just continuously monitor them, make sure they're not trending up, maybe do some other GLDH and biases, make sure there's nothing more significant going on, but probably don't worry about it. But obviously, as I said, if you've got more significant clinical signs or a marked GTT elevation, then you probably have got a hepatopathy that could cause some clinical symptoms.
So gastric ulcers, I know we're talking about laboratory analysis, and we're gonna sort of hint on that in a moment, but what studies have shown is that gastric ulcers actually have one of the biggest impacts on VO2 max, so in other words, the amount of oxygen that horses can intake during exercise. And so any horse that's presenting for poor performance should really be considered for gastroscopy, and that also normally fits with their diet and their lifestyle. So don't overlook gastroscopy as a tool during a poor performance examination.
But is there anything on blood work that can hint to you that these horses may have gastric ulcers without having to do a gastroscopy? This is a study in 2009 that looked at 10 normal horses versus 56 gastric ulcer cases. And what they did find was that there were some differences in bilirubin, alkaline phosphatase, GTT serum amyloid A.
But then a larger study in 2019, looking at 94 horses, over 114 gastroscopies, with a bigger spread of, of actual specific diseases, they found that there was absolutely no difference in serum amyloid A, with only 4 horses having an elevation in. In SAA, at all. And further studies that we've sort of been looking at, we, we were just partway through a study which we we've ended up stopping, showed that there's absolutely no correlation between blood work and gastric ulceration.
And I know there are supplements that are being sold with people touting they can tell the difference from bloods between gastric ulcer patients and non-gastric ulcer patients, but the research shows that there is no significant difference. It will help you out. And when you look at, sorry, one last point, when you look at the first study in 2009, if you actually look at the bilirubin, the AP, the GGT values, they're all tiny.
They, you know, those 31 GGT is not significant clinically. It's only the SAA that is, and this second study proved that there's no further correlation between SAA and gastric ulceration. What about cardiac markers, sorry, .
One study, this study by Dagmar in 2013. We're looking to say, does a murmur lead to increased myocardial damage during exercise? In other words, does an abnormal flow through a valve cause myocardial disease?
Now the one thing, important thing to consider is the cardiac troponin is only looking at muscle damage. So it may not elevate it unless there's severe damage, it normally takes about 4 hours to elevate, so it's not a great market in these sort of poor performance nebulous cases. But what these guys did is they looked at horses's mitral regurgitation only.
And they looked at the various different markers which, you know, aren't at this moment in time available to the general public. And what they found was there was no difference between normal and much regurgitation horses during exercise. And actual natrietic peptide did indicate that there was a little bit of increased stretch of myocardial tissue, but it wasn't definitive.
But what they found was that the results of this study indicated that atrial natri peptide is higher in horses with mild to severe m regurgitation, so we can see in that first graph that it is mildly elevated. And what they found was that that was characterised by an increased left heart's dimensions. But the normal capacity, excise capacity, and there was no absence of clinical signs of congestive heart failure at the same time, so is that value significant?
The AMP is partially related to the size of the heart, so they sort of said it's a surrogate for left left atrial pressures, both in healthy horses and horses with MR. So it could in time be a marker of severe cardiac pressure overloading. But with ass however, association with left atrium and left ventricular dimensions and function was less consistent, and in this study was only significant for a subset of the changes in healthy horses.
So in other words, what they found was that although atrial nitropeptide AMP was associated with stretch of the heart muscles, it was not associated with any evidence of clinical disease, and therefore is of limited use at this moment in time. What about blood gas analysis? Could blood gas analysis indicate improvements following training is the is the main question.
And blood gas analysis provides a complete analytical profile regarding both acid-based status and also oxygen status. And what it is really useful is all is for pulmonary function assessment. The primary acid-based modification during seen during exercise is usually indicated by a pH determination, both respiratory and metabolic components.
And that pH is commonly regulated by res respiration, so in other words, increased CO2 gets blown off by the by the lungs, serum buffers and also renal function. And gen and in humans, this has been massively investigated, although not so much in horses. What we can see though is that .
Although there are statistically significant changes in our blood gas analysis, those, those studies that have been performed are quite small, and therefore really quite difficult to assess in real life cases. In humans, there's been a huge amount of work looking at the consumption of oxygen in the period after exercise. In other words, we do a whole load of exercise, the oxygen is consumed, and then for 15 minutes after exercise, we see a continuous decrease in PO2.
And it's thought that that condition known as exercise, sorry, post excise oxygen consumption epoch is well known in human physiology, and it does have a role, and the thought is that it's by, it's hopefully replenishing the oxygen build up that oxygen jet debt buildup that was occurring during physical exercise. The role isn't completely understood and it is thought to occur in horses, but as I say, the studies have been small and are not particularly helpful. But what is helpful that we see on blood gas analysis is lactate.
And this is definitely something that we use a lot in any of these cases. So what is lactate? Lactate is produced during anaerobic glycolysis beyond the aerobic capacity of of the of the animal.
The edge is the one that we have validated in in horses at Lihook, and there are plenty of other . Lactate monitors that are out there, so that's not the only one, but it is very quick, very easy, and can be used by the horse. What we know is that the blood lactate will increase during exercise.
So this graph here shows that the heavier the exercise, the higher the blood lactate will go. And in some cases it can seem scarily high, but what can we use it for and how can we assess it fully in the horse? There are two ways to assess lactates.
One is, what's called a VLA 4, and that can be a 1st or multi-step, and I'm gonna go through each of these a little bit more, or we can do self-maximal exercising. The VLA 4 is the the velocity at which lactate reaches 4. And that's considered significant because aerobic to anaerobic threshold is, is thought to be at 4 millimoles per litre.
And so VLA 4 is the speed at which that horse's black tape reaches 4 millimoles and therefore that horse is going from aerobic to anaerobic exercise. The VLA 4 will always increase with fitness, and it is associated with performance, both good and bad, so the higher the velocity, the better the performance. And it's a really good index of aerobic capacity.
But when we consider lactate assessment, we have to really consider how we're going to do it. And what's what's really important is that you keep it consistent between for that horse. So in other words, if you have a horse, I don't know, a racehorse you're gonna do on the gallops.
You want to keep it on the gallops with that same hill, whereas say here we're gonna do it in the school and we're going to do it to set time, so we can control the surface, the incline, the decline of the of the, the area. The distance and duration, the acceleration and deceleration, and also the warm up and warm down of those horses. So it's really important that we control those things, but we can't control things such as temperature, humidity, wind or excitement.
So when we look at those things, if you say actually it's much worse today when the temperature was higher, then we've got to take that into account. But we have to take one step or multi-stop step. So a one step test is that we do a set piece of work, say 1000 metres, a slow drop for 5 minutes, followed by an 800 metre gallop for 1 minute.
And then a 5 minute trot, and then we take our venous sample and we can plot speed versus lactate throughout that period. What's important about this is that it's easily performed, you know, it's, it's very simple, we can very much set out what we're doing, and the one thing is that the horse has to be fit enough to do this, to be able to hit these sorts of levels. Also you have to have the equipment that's gonna attract the speed.
What we know is that the less fit the horse is, the more positive the lactate reading will be, because the lactate will go higher and higher as those horses have poor exercise tolerance, whereas the 5th of the horse, the negative the lactate reading is. But how do we do it? We compare the lactate result minus the predicted lactate.
And if positive, performing poorly, if negative, performing well. And this would seem to be relatively repeatable. So, these, these guys I think it was the Serrano paper, looked at 11 horses, and they all have the same rating, and the variability between the lactate was only 1.8.
So actually it's quite easy to, to, to do again and again. And the one thing is, does it work in real life? So this was, another, sorry, the first one was the Davi and Evans paper and this is the Serrano paper.
So these guys were looking at actual real life horses, so there's 13 advanced 3-day Adventers, and they have their lactate measured, after training sessions and also in phase D of the 3-star event. And what they found was that horse A had a significantly higher post lactate, post-training lactate compared to every single other horse. And that horse was the only one.
Only horse with no faults, and actually it did the worst out of all of them. So, you know, the higher the lactate is, the poorer that horse is going to do. Or you can do a multi-step lactate.
So this is where you just set warm up, make sure the horse is ready to go, and you repeat the same piece of work at different speeds multiple times, and again this requires the horse to be very fit. And what you need to then do is measure lactate at each step, so warm up for about 5 minutes a trot and do 4 or more steps. And they can be increasing speeds from 350 metres per minute, increasing by sort of 100 metres per minute every single time, and then rest between each step of the minute.
And that's gonna give you a really good indication of what speed, what level of exercise is going to affect that horse. But significantly, can training affect our VLA 4? Because obviously if it's not going to affect you, then what's the point in worrying about it?
What they found was that increasing training, increased the speed at which VLA 4 was reached. In other words, the faster the horse was going to go before it went into an aerobic exercise. But some studies have questioned how intense that exercise needs to be.
What they did was that they reduced intensity, so 30% less than the controls, and the 16 horses were split into two groups. And then they found that the VLA 4 actually didn't decrease, there was no statistical significance between the VLA 4 and those with a slightly less intense exercise regime. And the only difference was a slightly higher heart rate in those horses that weren't exercised as much.
So actually pushing horses to the absolute limit may not be the way to do, to increase the VLA for the most. And there's been a lot of work recently in humans showing that actually small short bursts of exercise are actually maybe better than longer term exercise. And actually this VLA 4, sorry, can be used to assess improvement following training.
In other words, it's really good if you're gonna look at these horses to say, OK, I want to take a test today, do exercise for 6, 12 weeks, whatever it is, and then see. And you can adjust training regimes very much depending on your VLA for, alterations, and you can work out when you hit that maximal point where you're not gonna get any more out of this horse. And that's obviously significant both for your race horses, but your Aventor and endurance horses.
What about electrolyte disturbances? Now, in the majority of horses in racehorses in Juventus, they're not exercising long enough to induce electrolyte disturbances. Now that's not always true if it's a very, very hot day with racehorses, you will see a lot of them having electrolyte abnormalities, but.
What we do see is that endurance horses will often suffer the most obvious electrolyte disturbances. And so this group over in America looked at 30 horses removed from competition early for any reason whatsoever. And then they compared their electrolytes to 10 normal horses that completed the competition.
And in every single case, they had low chloride, low potassium and low protein. And all of these were treated very easily with fluid therapy. But in each of those cases, they do, they felt that the electrolyte disturbance was significant and leading to poor performance.
And in severe cases, hypocalcemia, as we all know in racehorses can induce a synchronous diaphragmatic flutter. So in those courses, horses prone to electrolyte disturbances in insurance horses, what they found was that the electrolyte supplementation, in the, the run up to the the the endurance exercise, sorry, did resolve a lot of these electrolyte disturbances. So well worth considering in any of those horses.
And what about other supplements? Can other supplements help in our exercise and our poor performance? So in this study they looked at multidextrin, so just sugar.
There's been a lot of sort of speculative work saying that by supplementing multisection these horses are going to have a much better exercise, regime. And what they found though, or what they looked at, sorry, they said is could it affect insulin, lactate, corsol, glucose levels and exercise by reducing fatigue. They found no no difference at all, except a slightly increased cortisol levels, so Maltodextrin has no effect on exercise.
And what about lamburol? So obviously banned, you know, it's, it's, you can't use it in a lot of forces, but they sort of, this study said, OK, can it affect our muscle enzymes? Can CK ASD cardiac troponin.
And in that group, horses were randomly assigned to control groups or clambutrol groups, and we received that every 12 hours and 14 days. During that study, horses were subjected to some maximal treadmill exercise and muscle biopsies were taken before and afterwards, as well as taking echo results, blood results, serum callibuterol and cardiac troponin concentrations. What they found was there's no significant effect to Clembuterol on exercise, on any variable whatsoever, so that they, there was no significant, no adverse effects to giving Clembuterolol, but there was absolutely no positive effect on giving Clembuterol to horses, during training procedures.
And What about electrolytes? I've already mentioned in our endurance sources that they are helpful, but what about the use of electrolytes for intense exercise? And it has been shown to reduce the alteration in acid-based disturbances.
So horses had a decreased PCO2 and total CO2, in other words, they're gonna be less acidic. Horses were able to exercise for longer. And this was a crossover study, so direct comparisons were made between horses given electrolytes and horses that weren't given electrolytes.
The important thing though is to say in these cases, do not use the milkshakes that over in America they do with the sodium bicarb because that has a negative effect rather than a positive effect. So be sensible with your electrolytes supplementation. So in summary, haematological and biochemical parameters can be helpful.
And I think you have to make sure that you're going to always er interpret your results in line with the clinical symptoms. And consider the borderline results could still be normal for that course, or they may be abnormal. So in other words, if you have a very mild CK elevation and you are considering a CK, sorry, considering a mildopathy, then we need to look into it further with say post exercise CK and AST.
Subclinical disease is highly prevalent in our poor performance sources. So although it may not be obvious what is causing a poor performance, don't just look at orthopaedic. Let's think about that graph right at the beginning where this one of the smallest sections that caused poor performance was orthopaedic disease.
Look for respiratory disease, do a trackwah, do a BAL, because that is one of the most common reasons for poor performance. And use bloods as a guide to look for a definitive cause. Don't expect your answer to be there in the bloods, but hopefully it's going to guide you to the right answer.
Thank you very much for listening.
