Dr David Marlin on Electrolytes for horses
In this podcast Dr David Marlin will demystify electrolytes for horses, discussing where electrolytes come from, how electrolyte balance and imbalance and he will talk about electrolytes in the diet. David goes on to dispel some common myths about electrolytes in this 30 min podcast.
CLICK here to head over to the main Podcast page to see the complete list of podcasts available.
WANT MORE INFORMATION ON ELECTROLYTES?
- Webinar – Electrolytes for horses – never be confused again!
- Which supplement to buy – A Comparison of Commercial Electrolyte Product Formulations and Recommended Rates of Feeding
- Article – A simple guide to why and how to use electrolytes for horses
- Article – Electrolytes for horses – Never be confused again
TRANSCRIPTION:
Here is a transcription of the podcast. (Please note this is an automated transcription, so we apologise for any errors from the original podcast.)
Hi, my name is Dr David Marlin.
And in this podcast I’m going to try and demystify electrolytes for horses because this seems to be a topic that causes a lot of confusion.
And what I’m going to cover is what are electrolytes?
What they do where electrolytes come from.
I’m going to talk about electrolyte balance imbalance and I’m going to talk about electrolytes in the diet and I’m going to dispel some common myths about electrolytes.
So the first thing from a chemistry point of view,
we call an electrolyte a single pure chemical substance that can have a positive or negative charge.
Now that’s maybe not something you relate to.
So let’s take the example of salt,
salt,
the common name sodium chloride,
that’s its chemical name.
And it has a chemical formula N A C.
Which the represents sodium and the cl represents chloride.
So salt is a mixture of two different electrolytes,
sodium and chloride and sodium has a positive charge,
chloride has a negative charge.
And that effectively sticks these two chemicals together.
So the key thing about electrolytes are,
if we were to dissolve them in water,
it would produce a solution that will conduct electricity.
Whereas water that is pure doesn’t conduct electricity very well.
Now the main electrolytes that we find in the horse’s body are sodium potassium,
magnesium and calcium and these all have a positive charge.
And then we have bicarbonate chloride and phosphorus and these all have a negative charge.
What do electrolytes do?
Well,
they do so many different things.
They regulate thirst.
They are the way that nerves work,
they help muscles to contract.
They’re involved in bone and tooth formation.
They’re involved in energy production,
They’re involved in making DNA and RNA chloride is involved in making stomach acid.
So there’s lots of different essential things that electrolytes do in our body.
But electrics aren’t evenly distributed within the body.
So,
for example,
within our blood,
we have high sodium and chloride,
but low potassium.
Whereas inside cells we have high potassium and low sodium and chloride,
the opposite away.
Around Now 500 kg horses made up of around 300 liters of water.
And we divide this into two different what we call compartments.
One is what is called the CCF or extra cellular fluid compartment,
and that’s about one third 100 liters is in that compartment.
And that is the plasma,
what’s called interstitial fluid.
That’s the fluid sits between cells and the lymphatic system,
which returns fluid back into the circulation from the tissues and something we call trans cellular fluids,
which would include fluid that is inside the gastrointestinal tract.
Now, the majority,
twice as much 200 L is called the intracellular fluid and that is the fluid that’s actually within each cell of the body.
So for the fluid outside the cell is the 100 liters,
the plasma within the blood is about 30 liters and the gut contains about 50 liters of water.
Now the concentrations of electrolytes in different body compartments in a normally hydrated horse,
they do differ depending on which electrolyte we’re talking about.
And one of the confusing things perhaps is often when we talk about concentration,
um concentration can be confusing if you haven’t done chemistry for for a long while.
So for example,
concentration is the amount of something per volume.
So if we have one tennis ball in a bucket,
we have a concentration of one tennis ball per bucket.
If we put six in there in the same bucket,
we have six tennis balls per bucket.
So we have six times the concentration of tennis balls because the volume is the same,
but we’ve got more tennis balls in there.
So that’s a simple way of explaining it in tennis balls.
What about if we’re talking about salt or electrolytes?
So If we have,
we weigh out five mils,
sorry,
we don’t way out.
We would measure out five mils of salt.
That’s a sort of a teaspoon of salt that would weigh around about 10 g.
And if we have a bucket of 10 liters of water and we add 10 g of salt.
What’s the concentration?
Well,
we divide,
we have to convert our liters into milliliters.
And effectively what we have is one g in one liter.
Um so that would be the concentration.
So one g per 1000 mils or not .1% would be the concentration.
Now,
when we talk about concentrations of electrolytes,
we actually use a we use a term called million moles per liter,
which is a chemistry way of expressing how much of something there is in a liter or fluid And in the plasma there are 140 million moles of sodium and then about 100 million moles of chloride.
And there are very small amounts of actually a potassium calcium,
magnesium.
And that’s pretty much the same for the fluid that’s within the gut.
It has a very similar composition.
But when we looked at what is inside sales,
we find there’s very little sodium,
very little chloride,
very little actually calcium.
The main one is potassium and Whereas there’s about 140 million moles per liter of sodium in plasma and the gut there’s 100 and 40 million moles per liter of potassium inside the fluid in cells and the next highest concentration inside cells is actually magnesium.
Now,
electrolytes are incredibly important for thirst and thirst in the horse is regulated by the concentrations of sodium chloride and bicarbonate,
glucose and urea,
and also by a term we say,
osmolarity,
which is effectively the total strength,
osmotic strength of a fluid and it will have a higher osmotic strength.
The more electrolytes are in there.
And when it comes to thirst though the main electrolyte that regulates thirst as you probably will all know is sodium.
Now,
if you’re exercising or traveling your horse by the time your horses thirsty,
it’s likely to have already lost about 3% of its body weight and that would be in a 500 kg horse,
somewhere equivalent to around 15 liters of fluid.
Now that doesn’t for the horse present particularly problems.
And in fact,
horses probably,
well,
there’s good evidence they do exercise and perform better when they are slightly dehydrated,
which is very different to people where 1% dehydration has a clear negative effect on athletic performance.
So,
for example,
what we might see with endurance horses is that they would lose maybe three or 4% of their body weight on the first loop,
and then they might lose another couple of percent on the,
on the next loop.
So by the time they come in on loop two,
there around 5% dehydrated,
but then they start drinking and the interesting thing is they then run for the rest of the race around about this four or 5% dehydrated,
they don’t manage to replace all that fluid because they don’t need to.
As I say,
this fluid is drawn from the gut,
which acts as a reservoir and the fact that this fluid comes from there and the fact that blood flow to the gut reduces during exercise are two of the reasons why gut sounds are reduced during exercise in horses,
particularly during endurance type exercise.
So sodium is the key really to hydration and when a horse is normally hydrated,
it has a certain amount of sodium in the fluid in the body.
Now,
if that horse just drinks water,
the sodium becomes dehydrated,
becomes not dehydrated,
sorry,
it becomes the sodium concentration drops because we have the same amount of sodium,
but we’ve added in more water.
And the response of the body to that is driven by the kidney,
which will try to won’t even try.
It will,
it will actually do it.
It will excrete water until the sodium concentration in the blood is back to normal.
And this is a problem if we have dehydrated horses,
because if they are dehydrated and they drink only water,
then all that happens is the sodium is diluted.
The kidney senses this and excretes the water.
So in order to properly rehydrate,
the horse needs not only water but a source of sodium as well.
And this can come from the feed.
It can come from from hard feeds,
it can forage,
it can come from supplements added to the feed.
It can come from electrolyte syringes.
So,
if we increase the sodium in the blood,
this increases thirst,
we get increased drinking and we get increased hydration and horses may still be dehydrated or they may be dehydrated.
If their sodium is low,
they still will not drink.
And that’s the case where in sick horses,
they may often have to be given intravenous fluids because they are not drinking.
Now,
one of the myths we hear is that or this is a myth,
you may not be aware,
but you should not give electrolytes to a dehydrated horse that isn’t drinking.
Now,
the reason is,
or the rationale for this is that when you give electrolytes such as a syringe,
they draw water into the stomach and further dehydrate the horse.
But the problem here with this is that this isn’t how the body works.
If water was drawn into the gut,
this would decrease the amount of water in the blood,
and this would therefore relatively increase the concentration of sodium,
which would be a stimulus for the horse to drink.
Now,
on top of that,
the amount of water that could be drawn into the stomach by electrolytes would probably only be a few liters in any case.
So that would not significantly dehydrate the horse.
Nevertheless,
it is clear that often when we give dehydrated horses electrolytes in the form of a syringe,
it will start to,
it will stimulate drinking,
possibly because they don’t like the taste of the electrolyte or it’s too salty in their mouths.
So the important thing with horses is to try and maintain the levels of electrolytes in their body over a long period of time.
And this doesn’t have to be done on an hourly basis,
but on a weekly basis.
If the amount being excreted isn’t matched by more coming in,
then we get into deficiency and imbalance.
So intake comes from,
as we’ve already said,
from feeds from forage from supplements and losses are each day,
and these are primarily through urine and feces,
but if the horse is working,
this will also be through sweat of course,
and a small amount may well also be lost in the breath.
And over time as we’ve said,
these these intake and and loss must balance.
Otherwise we get deficiency or imbalances and these can lead to things such as reduced performance dehydration,
which may lead to gastrointestinal disturbance,
abnormal nerve function,
thumps or synchronized diaphragmatic flutter muscle dysfunction.
That may just be fatigue or it may actually be an episode of tying up.
And we may also,
in severe cases get compromised kidney function or kidney damage and different electrolytes may have different effects if they’re in balance.
For example,
high sodium loss can lead to high heart rate.
It can lead to low blood pressure.
It can lead to increased capillary refill time,
even potentially neurologic signs,
muscular spasms,
fatigue,
decreased thirst.
So what determines how much electrolyte your horse needs?
Well,
the main thing is going to be how hard your horse is working,
how much your whole sweats,
the weather and what you are feeding.
But we also have to take into account individual variation.
So what one horse needs may not be the same as what another horse doing exactly the same.
Work in the same climate on the same diet needs.
So we can of course work out how much electrolytes horses getting from its diet and work out if that diet is balanced.
However,
one of the problems with doing this is that not all of the electrolytes are absorbed To the same extent.
So,
for example,
horses will absorb almost all of the sodium chloride that they take in in the diet,
but they may only absorb around 50% of the potassium calcium and magnesium.
And again,
there is individual variation here,
whilst pretty much all horses will absorb most sodium and chloride calcium absorption in some horses,
maybe as low as 20% and in others as high as 70 80%.
So even if you know exactly what you’re feeding,
it may not be possible to know if your horse is deficient.
So from diet analysis,
it is one way that we can try to determine if your horse is getting at least in the right ballpark the amount of electrolytes.
So the big question here is how do you know if your diet is right or wrong with the respect to electrolytes?
Well,
it’s probably right if you’ve estimated how much is going in and how much is being lost if you’ve got a balanced diet,
if you’re hosting,
performing well if you’ve not got problems such as tying up or colic and if your host drinks normally and you might have a problem if diet analysis suggests a deficiency or imbalance if your horse has loss of performance,
especially over a long period of time,
especially if that happens during the summer,
if you’ve got episodes of tying up or colic or thumps,
these would all be signs that you may well have a problem with your electrolyte management.
So let’s look at some of the ways you can try to avoid having electrolyte problems.
The first is to do a diet analysis and we can do this from using published values that are available for common feed materials.
We can look at manufacturer’s labels,
although they don’t have to give you too much information about electrolyte.
They’re only required by law to actually put in the percentage of sodium in the feed.
And then of course,
we can actually analyze feeds or forages by sending them to a laboratory and in fact,
some of the feed companies do offer analysis of feeds or forage for you if you want to send particularly for forage and there are also independent companies that will do this if you want to try and work out how much your horse is losing in electrolytes.
So,
for example,
in sweat,
we can do this from published papers and that,
but this is quite complicated for owners to do,
um without the right access to the right information.
So we’ll explain in in a sec how you can potentially do that um,
when it comes to sweat,
sweat,
competition,
competition composition even does vary between different horses and it does vary over time.
Um,
it does,
it sweat is less rich in electrolytes when horses are heat acclimatized,
for example,
but interestingly,
sweat is highest in chloride and then sodium then potassium.
And with a small amount of calcium and horses produce what is called hyper tonic sweat.
So the concentrations of electrolytes in sweat are actually higher than in the plasma.
Whereas people by contrast produce what’s called isotonic sweat,
which is or hype a tonic sweat,
which is the same or lower concentration of electrolytes compared to the plasma.
Now,
one of the ways we can quickly get an idea of our electrolyte balance is to look at using something like feed Excel,
which is a software which you can use,
you put in all the values for your diet and it does a calculation for you and shows you where your imbalances are.
And if I took for example,
one that I’ve done before,
a 10 year old,
5 50 warm blood cross gelding in moderate work with no health issues On a diet of 17 kg of average quality grass hay per day.
I know that that will be a diet that is deficient,
particularly in sodium.
So how would I balance that well?
I could look at that just by giving adding to that diet,
60g of salt,
which would solve that problem.
And if I wanted to be really sure and balance out all the,
all the other components of the diet that might well be low on 17 kg per day.
Forage such as folic acid,
vitamin E.
iodine copper.
So trace minerals,
then I could add in a 60 g of concentrated vitamin and mineral supplement as well.
And that would fully balance that diet.
People often ask well,
what about blood tests?
Can’t I have a blood test to tell if my horses got adequate electrolytes.
Unfortunately,
blood tests only show up severe deficiencies.
The electrolytes in the blood,
even in horses are moderately to severely deficient.
If they’re still relatively healthy,
the concentrations will be normal concentrations of electrolytes in the plasma are altered by exercise.
They are altered by illness,
but as I say,
they are not a good indicator of whether your horse has adequate electrolytes and whether they are balanced.
So horses,
for example,
can have normal plasma calcium but be breaking down their bones to release calcium in order to maintain that plasma calcium concentration because for normal health,
normal physiological function,
it’s essential that those plasma concentrations are maintained within a very tight range.
Probably the best way we have that we can assess whole body electrolyte status in horses and and also in people.
Um and other animals is to use what’s called the urinary fractional electrolyte excretion test or the urinary creatinine clearance test.
And this is a test where we collect a sample of urine during mid flow.
Um we have to collect it before feeding and before exercise and then we have to get a blood sample within one hour of that urine.
And from that we can calculate the ratio of the electrolytes being excreted between the plasma and the urine.
And we use this marker called creatinine to assess the rate of clearance from the plasma and that is our best way of working out if a horse’s diet is adequate for it in terms of electrolytes,
electric supplements added to feed are the simplest way to restore on a regular daily basis.
These are usually if they’re palatable.
Um it cannot,
you know,
if the horse will eat them on their own without the feed,
they probably are very high in sugar and very low in electrolytes.
So that’s something to watch out for the important thing to look for is the sodium content on the label.
Um But the key thing with feeding electrolyte supplements is to feed them on a daily basis according to the level of work your horses in at that time.
So if your horse is in moderate work,
you feed according to moderate work on a daily basis.
Don’t try to add to a just say,
well,
my whole saturday off.
So I won’t give any.
And then my horse has done hard work today.
So I’ll give twice as much if you feed the same amount over that a week or so,
the kidney will sort itself out and work out what it needs to keep and what it needs to get rid of one.
Key point here is don’t try and load before competitions.
Um I often see people trying to double up or treble up,
even what they’re feeding as they come up to a competition,
it’s not gonna work.
The horse isn’t going to store that and you may well just put your horse off its feed or cause other problems which are actually gonna discuss in just a second.
Um There is some evidence that concentrated electrolytes or high electrolyte intake can irritate the gastric mucosa and lead to gastric ulcers,
or if horses have them already may well worsen them.
Um So that’s just one thing to be careful of.
There are some supplements around electrolyte supplements,
that where the electrolytes themselves are coated in a fact,
which means that they are,
that protects the mucosa because it’s the fact that comes in contact,
not the electrolyte.
If you think of,
for example,
if you have a graze on the back of your hand,
that might be like having a horse having an ulcer in the stomach.
If you were to put salt or electrolytes on that,
then that would cause a lot of pain.
And and that’s in fact what probably does happen with horses with gastric horses when they ordinary electrolytes.
So,
the,
the problem really is that electrolyte is quite complicated subject and there are quite a few myths out there.
Now,
one of them is that if you give a horse free access to a mineral block or a salt lick,
that it will be able to adequately self regulate how much salt it needs.
Now,
we have a number of studies that have shown this actually doesn’t happen often.
Horses don’t touch them at all,
or they eat them way too too much,
possibly through boredom in a very short period.
I say.
Unfortunately,
horses are not able to regulate their electrolyte intake from having free access to ad lib electrolytes,
if you like.
Another myth is that glucose or other sugars are essential for absorption of electrolytes from the stomach or small intestine.
This simply isn’t true.
There’s no evidence for that.
They’re they’re purely for palatability.
As we said,
you should not increase your electrolytes coming into a competition that is just going to cause problems.
Uh One of the other myths is that horses can’t store electrolytes.
Yes,
they can keep electrolytes in the body.
What they can’t do is store extra if you try to put more in,
that will just result in them drinking more and producing more urine.
There’s lots of different types of electrolytes out there.
There’s liquid ones,
there’s ones which are powders,
there’s pellets,
there’s chill ated minerals in them.
There’s sugars,
there’s buffered flavored everything,
whatever you want.
You can find liquid ones to me are pretty much a waste of time because they’re not very,
not very concentrated.
There’s not much electrolyte in there.
Um and many of the syringes don’t actually have very much electrolyte in them.
Lots of them electrolytes.
The powder ones are pretty much full of sugar and you don’t get very much electrolyte.
So what should you look out for an electrolyte supplement?
Well,
you’re looking for sodium chloride,
potassium calcium and magnesium and you’re looking for sodium to be one of the main ingredients.
Some of them do have other things in such as phosphorous,
sulfate,
bicarbonate,
citrate,
glucose,
lactate.
These may be beneficial.
There’s not great evidence that they are.
So take less notice of those.
And then finally there are things included in electrolyte supplements such as manganese,
zinc,
iron,
vitamins,
pectin,
ascorbic acid,
B vitamins and and false fructose.
Sacha rides these don’t need to be in there and they’re not they’re a waste of time in an electrolyte supplement.
If you look at how much electrolyte you’re getting per syringe,
you might find you’re quite surprised.
Some of the popular ones,
such as apple lights only have around 5g of electrolyte per syringe,
which is gonna be a waste of time.
A good one should have at least 25,
maybe 35,
30,
35 g of electrolyte per syringe because that’s what you’re going to need to have an effect on on the horses drinking or electrolyte replacement.
You can overfeed electrolytes.
Um this usually results in the horse not wanting to eat its feed.
If they do eat the feed with high electrolytes in,
then you get excessive drinking and you get excessive urine.
The urine is very pale,
the floors incredibly wet.
You may also get loose droppings and you may also start to get problems with gastric ulceration.
But in my experience over supplementation is very rare and under supplementation is extremely common.
So does my horse need electrolytes?
Does your horse need electrolytes?
Most horses would benefit from 125 mil scoop of salt per day.
That’s around 50 g of salt.
If they’re in work to that,
I would add a balanced electrolyte called into the level of work there and at that time,
light,
medium,
hard competing in warm weather.
You would want salt pass electrolytes as well.
You may want to increase those amounts,
particularly the electrolytes,
and for some horses there special consideration.
So,
for example,
horses that tie up may well want more electrolytes and horses that have experienced a number of bouts of imp action colic.
I would put more salt and electrolytes into their diet to try and encourage more drinking and better level of hydration.
So the key points here electrolytes have to be obtained from the diet because horses cannot make them electrolytes are lost every day,
primarily in the urine and feces and in sweat.
If the horses are in work,
Most horse diets are low in sodium,
so one times 25 men have sought a day is a good move.
Horses are much more like to be under,
supplemented with respect to electrolytes and over supplemented horses can store electrolytes in their body.
They can keep them in the body,
but if you feed an excess it will be excreted,
even if your horse is deficient,
if you suddenly put a lot more into the diet,
it will excrete a lot of that,
and it will retain a small amount and build that up over time to get back to normal mm.
Horses do not regulate their electrolyte intake themselves very well from having free access to salt or mineral licks.
So the best approach is to put them into the diet,
and the best approach from this is to feed daily with a slight excess and then the kidney will sort itself out.
Thanks very much.
I hope that’s answered a lot of your questions about electrolyte management in horses by by.
