Anyone else had symptoms like this?

[JBM]

My vet is weary of this supplement right now and has told me to take him off it as he think he’s getting too much iodine from the seaweed? I think he said was something about the seaweed but I’m unsure

 

[Barton Bounty]

My vet is weary of this supplement right now and has told me to take him off it as he think he’s getting too much iodine from the seaweed? I think he said was something about the seaweed but I’m unsure

Yeah best get that stopped and just keep making sure he is drinking plenty, i know he has a drinker but maybe give him a bucket too just so you can monitor?

 

[JBM]

Yeah best get that stopped and just keep making sure he is drinking plenty, i know he has a drinker but maybe give him a bucket too just so you can monitor?

Yes I think that would be a good idea for now last prognosis I expected a bit in shock a slow heartbeat sounds very bad

 

[Rowreach]

My vet is weary of this supplement right now and has told me to take him off it as he think he’s getting too much iodine from the seaweed? I think he said was something about the seaweed but I’m unsure

I would never ever feed seaweed!! It seems to be a bit of a thing in Ireland, a bit of a fashion thing but definitely one to avoid.

 

[JBM]

I would never ever feed seaweed!! It seems to be a bit of a thing in Ireland, a bit of a fashion thing but definitely one to avoid.

I know now at least! Was suggested by a good (or so I thought) nutritionalist and had great reviews but never again ?

 

[nutjob]

Thanks for updating @Katie&Judy, it's an interesting and unusual diagnosis. Seaweed used to be a common supplement but I don't think it's much recommended now. Hope your horse makes a quick and full recovery and you do also. I am very thankful that we have a faster emergency call out service here, they can be so worrying.

 

[JBM]

He’s already perked up a lot eating and drinking normally again

 

[JBM]

Just want to thank everyone for their help and kind words ?? Barry will never be fed seaweed again!!
Unfortunately there is just not enough vets in ratio to the amount of animals around here but thankfully it worked out okie after being stressed for only like 8 hours ??‍

 

[nagblagger]

Good news, thanks for the update. When i had my first horse 40 + years ago seaweed powder was the 'in thing' to feed them. Interesting diagnosis, keep us updated, we have been there with you in spirit, for the 8 hrs !

 

[JBM]

Good news, thanks for the update. When i had my first horse 40 + years ago seaweed powder was the 'in thing' to feed them. Interesting diagnosis, keep us updated, we have been there with you in spirit, for the 8 hrs !

Very much appreciated I am a worrier on a normal day! My heart still hasn’t calmed down ?
Will keep you guys in the loop
Was definitely strange and not expected was very sold on it being either colic or ulcers or both!

 

[[153312]]

crikey what a rollercoaster! SO pleased you have some answers now op and hope Barry continues to improve.

 

[JBM]

crikey what a rollercoaster! SO pleased you have some answers now op and hope Barry continues to improve.

Thank you so much me too! He’s already looking much better

 

[PurBee]

My vet is weary of this supplement right now and has told me to take him off it as he think he’s getting too much iodine from the seaweed? I think he said was something about the seaweed but I’m unsure

At 0.15mg per kg iodine in that supplement, at a dose of 25g = 0.00375mg per 25g scoop.
The RDA of iodine is 3.5-5mg per day for a 500kg horse. Upper toxic limit is 50mg.

The iodine dose in that supplement is infinitesimally small that it absolutely isn’t the issue. All other equine feed bags contain vastly more iodine than that supplement.

That supplement isnt pure seaweed - it has majority other bulking ingredients.

Weirdly its main ingredient is lithithamnium algae which isnt like soft seaweed leaves - its more like a coral tree growing at massive depths in the atlantic ocean, which has a red bloom of algae growing on it. Its main component is a hard calcium tree-like structure, so thats not a high iodine ‘seaweed’ either. Neither is the other seaweed a high dose seaweed, as they all vary in iodine content.

It’s weird like i say, as they have that as an ingredient, then mag ox, then more calcium added ontop of the calcium coral algae main ingredient.

The other nodosa leaf-like seaweed in that product is a small amount to yield such a small iodine analysis per kg.
Basically, that is 5kg of very expensive calmag - with some yeast n other cheap minerals! It doesnt even cover the horses RDA for iodine!

The problem i see with the supplement is its high calcium content. Its mainly a bucket of calcium powder - with other teeny doses of micro minerals, not worth the 5kg for 150 odd euro’s though!
(Truly these feed companies p*ss me off with their marketing BS - a 25kg bag of organic atlantic nodosa safe iodine seaweed is 30 euro, yeast is cheap, calcium powder per 25kg - dirt cheap)

The thing is - hay/haylage is high in calcium, low in magnesium, low in phosphorus.If NPK was added as fertiliser to your hay field (if you know, many commercial large farms do, smaller farms use manure) your hay will have a higher potassium level than non-fert fields.

So, you have 2x25g scoops of calcium+ some magnesium = 50g cal/mag mix roughly (unfortunately we’re not told how much grams per kilo of calcium or magnesium are in this supplement ?) but it’s a lot considering average daily dose is around 20grams calcium per day - roughly, non-working horse.
Considering he’s eating hay/lage thats bound to have a healthy enough calcium dose for his daily needs, this would easily spill his calcium dose over the top, with him needing vastly more phosphorus/potassium for balance, IF you were going to continue feeding this.

So my maths on this shows calcium topping as a high dose in his diet compared to phosphorus and potassium.
Dont add phosphorus or potassium, just stop the supplement.

The electrolytes are central to heart health. Any imbalance of them out of preferred ranges gives either fast heart rate, or slow heart rates. Other changes too but heart health is dependent on the electrolytes being in balance.
I’ve just spent a while trying to find a chart/article explaining the balance of these electrolytes easily and simply but drew a blank. There’s many in-depth articles on heart function and electrolytes with horses.

High calcium can cause bradycardia. Slow heart beat. The kidneys will try to flush out excess calcium but can become taxed, especially in an older horse. kidney crystals can form and as you mentioned, they try to pee, but can’t. Excess peeing = high calcium diet.
The slow heart rate causes an exhaustion, laying down, colic-type symptoms.

Colic and mag/cal deficiency usually cause fast heartbeats and agitation - high calcium its the opposite, lethargy, off their food.

I’d stop the supplement due to the calcium not due to the paltry iodine content.
I’d push your vet for kidney function tests and blood electrolyte levels.
The potassium and phosphorus content of the supplement dont balance out the calcium or magnesium. Its a terrible supplement for imbalanced minerals. This would work for a horse fed majority grain mixes, who doesnt get much forage at all.

Now youve stopped the supplement that’ll be a huge help to prevent such a high dose of calcium in his diet, and should bring him round fairly quickly - but if he’s been on the supplement for some time, its wise to get kidneys checked out.

Also a urethral ‘bean’ blocking peeing can cause calcium backing-up into the kidneys causing these issues. Worse situation if on a high calcium supplement, and has a bean blocking peeing.

Did you get to check for a bean? Or your vet?

The only other thing i can think of thats a tenuous possibility, is some algaes have nasty bacteria growing on them. This lithithamnium with its red algae that grows on the calcium structure is a possibility. Usually these nasty bacterias are found in algae of fresh water ponds/lakes, rather than salt water. However, we dont know all bacterias in the world, and it may be that some oceanic algae may also have a salt-water thriving bacterial potential.
That would induce colic etc, but toxicity usually presents with fast heart beat/shivers/agitation etc.
Also, these collected/harvested algaes and seaweeds are normally dried in massive kilns of incredibly high temps, to kill off bacterial baddies, before being ground-up for food stuff and supplements.

Usually dogs gets poisoned when walked by lakes with algae blooms if they swim in them or drink the water. Its colic/trembling/vomiting etc. quite obvious a toxin is involved.
This is informational really to avoid algae-type waters of streams/ rivers /ponds near paddocks etc. They’re high potential to be very toxic.

I hope your boy continues to improve over the next few days. Such a sweet picture of him ?

 

[TheMule]

At 0.15mg per kg iodine in that supplement, at a dose of 25g = 0.00375mg per 25g scoop.
The RDA of iodine is 3.5-5mg per day for a 500kg horse. Upper toxic limit is 50mg.

The iodine dose in that supplement is infinitesimally small that it absolutely isn’t the issue. All other equine feed bags contain vastly more iodine than that supplement.

That supplement isnt pure seaweed - it has majority other bulking ingredients.

Weirdly its main ingredient is lithithamnium algae which isnt like soft seaweed leaves - its more like a coral tree growing at massive depths in the atlantic ocean, which has a red bloom of algae growing on it. Its main component is a hard calcium tree-like structure, so thats not a high iodine ‘seaweed’ either. Neither is the other seaweed a high dose seaweed, as they all vary in iodine content.

It’s weird like i say, as they have that as an ingredient, then mag ox, then more calcium added ontop of the calcium coral algae main ingredient.

The other nodosa leaf-like seaweed in that product is a small amount to yield such a small iodine analysis per kg.
Basically, that is 5kg of very expensive calmag - with some yeast n other cheap minerals! It doesnt even cover the horses RDA for iodine!

The problem i see with the supplement is its high calcium content. Its mainly a bucket of calcium powder - with other teeny doses of micro minerals, not worth the 5kg for 150 odd euro’s though!
(Truly these feed companies p*ss me off with their marketing BS - a 25kg bag of organic atlantic nodosa safe iodine seaweed is 30 euro, yeast is cheap, calcium powder per 25kg - dirt cheap)

The thing is - hay/haylage is high in calcium, low in magnesium, low in phosphorus.If NPK was added as fertiliser to your hay field (if you know, many commercial large farms do, smaller farms use manure) your hay will have a higher potassium level than non-fert fields.

So, you have 2x25g scoops of calcium+ some magnesium = 50g cal/mag mix roughly (unfortunately we’re not told how much grams per kilo of calcium or magnesium are in this supplement ?) but it’s a lot considering average daily dose is around 20grams calcium per day - roughly, non-working horse.
Considering he’s eating hay/lage thats bound to have a healthy enough calcium dose for his daily needs, this would easily spill his calcium dose over the top, with him needing vastly more phosphorus/potassium for balance, IF you were going to continue feeding this.

So my maths on this shows calcium topping as a high dose in his diet compared to phosphorus and potassium.
Dont add phosphorus or potassium, just stop the supplement.

The electrolytes are central to heart health. Any imbalance of them out of preferred ranges gives either fast heart rate, or slow heart rates. Other changes too but heart health is dependent on the electrolytes being in balance.
I’ve just spent a while trying to find a chart/article explaining the balance of these electrolytes easily and simply but drew a blank. There’s many in-depth articles on heart function and electrolytes with horses.

High calcium can cause bradycardia. Slow heart beat. The kidneys will try to flush out excess calcium but can become taxed, especially in an older horse. kidney crystals can form and as you mentioned, they try to pee, but can’t. Excess peeing = high calcium diet.
The slow heart rate causes an exhaustion, laying down, colic-type symptoms.

Colic and mag/cal deficiency usually cause fast heartbeats and agitation - high calcium its the opposite, lethargy, off their food.

I’d stop the supplement due to the calcium not due to the paltry iodine content.
I’d push your vet for kidney function tests and blood electrolyte levels.
The potassium and phosphorus content of the supplement dont balance out the calcium or magnesium. Its a terrible supplement for imbalanced minerals. This would work for a horse fed majority grain mixes, who doesnt get much forage at all.

Now youve stopped the supplement that’ll be a huge help to prevent such a high dose of calcium in his diet, and should bring him round fairly quickly - but if he’s been on the supplement for some time, its wise to get kidneys checked out.

Also a urethral ‘bean’ blocking peeing can cause calcium backing-up into the kidneys causing these issues. Worse situation if on a high calcium supplement, and has a bean blocking peeing.

Did you get to check for a bean? Or your vet?

The only other thing i can think of thats a tenuous possibility, is some algaes have nasty bacteria growing on them. This lithithamnium with its red algae that grows on the calcium structure is a possibility. Usually these nasty bacterias are found in algae of fresh water ponds/lakes, rather than salt water. However, we dont know all bacterias in the world, and it may be that some oceanic algae may also have a salt-water thriving bacterial potential.
That would induce colic etc, but toxicity usually presents with fast heart beat/shivers/agitation etc.
Also, these collected/harvested algaes and seaweeds are normally dried in massive kilns of incredibly high temps, to kill off bacterial baddies, before being ground-up for food stuff and supplements.

Usually dogs gets poisoned when walked by lakes with algae blooms if they swim in them or drink the water. Its colic/trembling/vomiting etc. quite obvious a toxin is involved.
This is informational really to avoid algae-type waters of streams/ rivers /ponds near paddocks etc. They’re high potential to be very toxic.

I hope your boy continues to improve over the next few days. Such a sweet picture of him ?

Brilliant post, the OP should be immensely grateful for such detailed analysis!

 

[JBM]

At 0.15mg per kg iodine in that supplement, at a dose of 25g = 0.00375mg per 25g scoop.
The RDA of iodine is 3.5-5mg per day for a 500kg horse. Upper toxic limit is 50mg.

The iodine dose in that supplement is infinitesimally small that it absolutely isn’t the issue. All other equine feed bags contain vastly more iodine than that supplement.

That supplement isnt pure seaweed - it has majority other bulking ingredients.

Weirdly its main ingredient is lithithamnium algae which isnt like soft seaweed leaves - its more like a coral tree growing at massive depths in the atlantic ocean, which has a red bloom of algae growing on it. Its main component is a hard calcium tree-like structure, so thats not a high iodine ‘seaweed’ either. Neither is the other seaweed a high dose seaweed, as they all vary in iodine content.

It’s weird like i say, as they have that as an ingredient, then mag ox, then more calcium added ontop of the calcium coral algae main ingredient.

The other nodosa leaf-like seaweed in that product is a small amount to yield such a small iodine analysis per kg.
Basically, that is 5kg of very expensive calmag - with some yeast n other cheap minerals! It doesnt even cover the horses RDA for iodine!

The problem i see with the supplement is its high calcium content. Its mainly a bucket of calcium powder - with other teeny doses of micro minerals, not worth the 5kg for 150 odd euro’s though!
(Truly these feed companies p*ss me off with their marketing BS - a 25kg bag of organic atlantic nodosa safe iodine seaweed is 30 euro, yeast is cheap, calcium powder per 25kg - dirt cheap)

The thing is - hay/haylage is high in calcium, low in magnesium, low in phosphorus.If NPK was added as fertiliser to your hay field (if you know, many commercial large farms do, smaller farms use manure) your hay will have a higher potassium level than non-fert fields.

So, you have 2x25g scoops of calcium+ some magnesium = 50g cal/mag mix roughly (unfortunately we’re not told how much grams per kilo of calcium or magnesium are in this supplement ?) but it’s a lot considering average daily dose is around 20grams calcium per day - roughly, non-working horse.
Considering he’s eating hay/lage thats bound to have a healthy enough calcium dose for his daily needs, this would easily spill his calcium dose over the top, with him needing vastly more phosphorus/potassium for balance, IF you were going to continue feeding this.

So my maths on this shows calcium topping as a high dose in his diet compared to phosphorus and potassium.
Dont add phosphorus or potassium, just stop the supplement.

The electrolytes are central to heart health. Any imbalance of them out of preferred ranges gives either fast heart rate, or slow heart rates. Other changes too but heart health is dependent on the electrolytes being in balance.
I’ve just spent a while trying to find a chart/article explaining the balance of these electrolytes easily and simply but drew a blank. There’s many in-depth articles on heart function and electrolytes with horses.

High calcium can cause bradycardia. Slow heart beat. The kidneys will try to flush out excess calcium but can become taxed, especially in an older horse. kidney crystals can form and as you mentioned, they try to pee, but can’t. Excess peeing = high calcium diet.
The slow heart rate causes an exhaustion, laying down, colic-type symptoms.

Colic and mag/cal deficiency usually cause fast heartbeats and agitation - high calcium its the opposite, lethargy, off their food.

I’d stop the supplement due to the calcium not due to the paltry iodine content.
I’d push your vet for kidney function tests and blood electrolyte levels.
The potassium and phosphorus content of the supplement dont balance out the calcium or magnesium. Its a terrible supplement for imbalanced minerals. This would work for a horse fed majority grain mixes, who doesnt get much forage at all.

Now youve stopped the supplement that’ll be a huge help to prevent such a high dose of calcium in his diet, and should bring him round fairly quickly - but if he’s been on the supplement for some time, its wise to get kidneys checked out.

Also a urethral ‘bean’ blocking peeing can cause calcium backing-up into the kidneys causing these issues. Worse situation if on a high calcium supplement, and has a bean blocking peeing.

Did you get to check for a bean? Or your vet?

The only other thing i can think of thats a tenuous possibility, is some algaes have nasty bacteria growing on them. This lithithamnium with its red algae that grows on the calcium structure is a possibility. Usually these nasty bacterias are found in algae of fresh water ponds/lakes, rather than salt water. However, we dont know all bacterias in the world, and it may be that some oceanic algae may also have a salt-water thriving bacterial potential.
That would induce colic etc, but toxicity usually presents with fast heart beat/shivers/agitation etc.
Also, these collected/harvested algaes and seaweeds are normally dried in massive kilns of incredibly high temps, to kill off bacterial baddies, before being ground-up for food stuff and supplements.

Usually dogs gets poisoned when walked by lakes with algae blooms if they swim in them or drink the water. Its colic/trembling/vomiting etc. quite obvious a toxin is involved.
This is informational really to avoid algae-type waters of streams/ rivers /ponds near paddocks etc. They’re high potential to be very toxic.

I hope your boy continues to improve over the next few days. Such a sweet picture of him ?

Wow your knowledge is absolutely amazing thank you so much
I was going to get bloods done on Monday but I will defo get them done now and make it clear I want kidneys checked
I attempted to clean out his sheath a few times but he rarely drops, didn’t feel one while up there but unsure if it’s harder to feel when he isn’t dropped
will ask the vet to check too!
Incredibly helpful thank you ?? his symptoms make so much sense now

 

[JBM]

He’s been on the supplement 44 days which is kinda weird as it’s a 30 day supply I bought so potentially not getting the two scoops a day only one
Have to ask yard manager when I see her

 

[SpotsandBays]

@PurBee what a fantastic response!
We’ve had experience with too much calcium causing us an issue, but with a ram.
Usually remove the ram from the flock of ewes once they’ve all been covered, however we decided to leave him in with them a couple of years ago.
One day we went out and he was up and down, up and down and trying to pee. Looked like he was getting ready to have a lamb himself! Vet called, after investigating abit, she…

Spoiler: Cringe warning!

snipped off the top of his penis (about 1-2mm), and it went off like a fire hose!!!

The feed we were giving the ewes for their pregnancy was too high in calcium for the ram, causing small crystals to build up and it had created a blockage. After the procedure, he was instantly relieved of his discomfort. For a few days we had to drench him with some apple cider vinegar (which he hated!!!) but after that - and removing him from the feed source, he didn’t have that issue again.

 

[JBM]

@PurBee what a fantastic response!
We’ve had experience with too much calcium causing us an issue, but with a ram.
Usually remove the ram from the flock of ewes once they’ve all been covered, however we decided to leave him in with them a couple of years ago.
One day we went out and he was up and down, up and down and trying to pee. Looked like he was getting ready to have a lamb himself! Vet called, after investigating abit, she…

Spoiler: Cringe warning!

snipped off the top of his penis (about 1-2mm), and it went off like a fire hose!!!

The feed we were giving the ewes for their pregnancy was too high in calcium for the ram, causing small crystals to build up and it had created a blockage. After the procedure, he was instantly relieved of his discomfort. For a few days we had to drench him with some apple cider vinegar (which he hated!!!) but after that - and removing him from the feed source, he didn’t have that issue again.

I’m hoping I don’t have to do that to poor barry!! As he is peeing now ?? poor ram ?

 

[SpotsandBays]

I’m hoping I don’t have to do that to poor barry!! As he is peeing now ?? poor ram ?

I’m sure it would definitely be handled differently for a horse ? honestly I thought the ram would kick out or something but he was just so relieved to get rid of that full bladder bless him!

 

[JBM]

Brighter this morning standing waiting for breakfast and eating as usual!

 

[PurBee]

He’s been on the supplement 44 days which is kinda weird as it’s a 30 day supply I bought so potentially not getting the two scoops a day only one
Have to ask yard manager when I see her

Its so hard to calculate exactly the minerals theyre getting when feed supplement companies dont detail ALL the ingredients in grams per dose.
With your supplement we get some detail on some amounts per kilo, but not for the calcium or magnesium levels which is the majority of the product, so we can only guess - but even if he got 1 scoop of 25grams - that could be @20g of calcium that would spill over the edge of his daily needs, when we factor in hay/lage consumption and him not being worked.
If he was given the usual beet pulp to add minerals supplement in, thats really high in calcium too.

What a blessing he wasnt given full dose of 2 scoops!

Glad to hear he’s peeing and perky this morning. Sounds like he doesnt have a huge bean blockage, but possibility of kidney crystals which a kidney test should help assess.

Is your YO experienced at ‘bean hunting’?! Maybe get them to try to have a check too, if he’s ok with being fiddled with ?

 

[JBM]

Its so hard to calculate exactly the minerals theyre getting when feed supplement companies dont detail ALL the ingredients in grams per dose.
With your supplement we get some detail on some amounts per kilo, but not for the calcium or magnesium levels which is the majority of the product, so we can only guess - but even if he got 1 scoop of 25grams - that could be @20g of calcium that would spill over the edge of his daily needs, when we factor in hay/lage consumption and him not being worked.
If he was given the usual beet pulp to add minerals supplement in, thats really high in calcium too.

What a blessing he wasnt given full dose of 2 scoops!

Glad to hear he’s peeing and perky this morning. Sounds like he doesnt have a huge bean blockage, but possibility of kidney crystals which a kidney test should help assess.

Is your YO experienced at ‘bean hunting’?! Maybe get them to try to have a check too, if he’s ok with being fiddled with ?

Definitely! I wish I had the extensive knowledge you have it’s hard to know what to feed!
Aye definitely get him tested. Are crystals reversible?
He tolerates it I’d say but I’ll probably get the vet to have a look on Monday

 

[PurBee]

Definitely! I wish I had the extensive knowledge you have it’s hard to know what to feed!
Aye definitely get him tested. Are crystals reversible?
He tolerates it I’d say but I’ll probably get the vet to have a look on Monday

Calcium crystals and stones break down easier than other mineral stones. As he’s been on the supplement just for the month thats usually not long to have caused a severe stone formation problem blocking his kidneys, just likely excessive crystals that should flush through. Providing the excess calcium is stopped in the diet thats causing the crystals.

Unfortunately, because hays and other common forages are usually higher in calcium than mag/pot/phos minerals - in older horses there can be kidney issues with excess calcium deposits that have accumulated throughout life eating forage.
Hence why adding calcium supplements can easily tip them over the edge.

(Calcium regulation involves the parathyroid glands, and these glands in the older horse can operate less efficiently allowing too much calcium in the blood, rather than shunting it to be excreted by kidneys)

Calcium really is only needed extra supplemented by racehorses and other high intensity worked horses, as they wont get enough from hay alone. Theyre usually given grains too, to add more phosphorus to balance the high calcium input.

Your boy is older, at rest/light work….so a simple mixed grass hay diet, with some balancer minerals should keep major minerals balanced.

You weren’t to know that supplement was imbalanced as they dont say, and they all have some marketing spiel to make it sound like every horse needs their supplement!

Hay diets are simple - with added ‘balancer’ minerals commonly missing in hays added, to balance mineral ratio’s. This goes a long way to preventing older horse kidney issues.

If you have a hay supplier you use all the time, its worth getting a hay sugar/protein and mineral analysis. You’ll know the average levels, and can know what’s hugely out of balance - then can add whatever is really deficient in the hay to balance it exactly. Usually that’s magnesium, phosphate, zinc, copper. Sometimes potassium.

A kidney test by vet can help determine if he’s struggling. For him to be better from having 1 day off the dose, less calcium in the blood, he’s likely got a better heart rate too, and he can now flush excess easily from his system.

 

[Dexter]

Surely if the supplement caused all of this other horses would be affected? Its clearly a terrible thing to feed, but I just can't see how it can cause such extreme symptoms yet no other horses are affected by it. OP was recommended it by someone so clearly there are horses not just ok, but doing well on it.

 

[PurBee]

Surely if the supplement caused all of this other horses would be affected? Its clearly a terrible thing to feed, but I just can't see how it can cause such extreme symptoms yet no other horses are affected by it. OP was recommended it by someone so clearly there are horses not just ok, but doing well on it.

Yes, working horses could tolerate it if theyre also getting enough phosphorus, which most do as working horses are usually given bagged phosphorus-heavy Feeds.
OP’s older horse is practically retired, at rest, and simply the double in calcium RDA (at least) occurring from the supp and forage can easily cause accumulation and consequent high calcium symptoms/kidney/pee symptoms

 

[Dexter]

Yes, working horses could tolerate it if theyre also getting enough phosphorus, which most do as working horses are usually given bagged phosphorus-heavy Feeds.
OP’s older horse is practically retired, at rest, and simply the double in calcium RDA (at least) occurring from the supp and forage can easily cause accumulation and consequent high calcium symptoms/kidney/pee symptoms

OPs horse is a young and growing TB, her other one is older and retired. It hasn't been getting the full dose, and its a very, very short time for kidney stones/crystals to form or symptoms of high calcium to show, then within 12 hours or so of stopping the supplement the horse is back to normal.

While I'm not disputing what you are saying, it doesn't add up. The amounts given, the duration given, the timescales for recovery and the fact that no other horses have shown these symptoms. Theres been issues with the horse prior to this supplement being started as well.

I think OP is playing with fire to accept that the supplement is the cause without question and further investigation.

 

[PurBee]

OPs horse is a young and growing TB, her other one is older and retired. It hasn't been getting the full dose, and its a very, very short time for kidney stones/crystals to form or symptoms of high calcium to show, then within 12 hours or so of stopping the supplement the horse is back to normal.

While I'm not disputing what you are saying, it doesn't add up. The amounts given, the duration given, the timescales for recovery and the fact that no other horses have shown these symptoms. Theres been issues with the horse prior to this supplement being started as well.

I think OP is playing with fire to accept that the supplement is the cause without question and further investigation.

I agree further investigations / bloodwork should be done to assess the older horse.

Im only going by info provided by op in this thread, im not aware of other issues.
My suggestions of cause are due to the weird low heart rate, which excess calcium in blood can cause, and the difficulty peeing symptoms - points to calcium. It presents like colic but the additional symptoms suggest another element. Coupled with the fact the vet intuitively thought the supplement, i looked into that further.

1 older horse and 1 younger horse can react differently to the same supplement due to different gland health/metabolism/feeds/work load.
Urinary health of older horse compared to younger horse also would mean a younger horse is likely to have healthier kidneys to flush out excess than an older horse.
The parathyroid glands regulate calcium and their condition in the older horse compared to young can be different. Hyperparathyroidism is more common in elderly mammals, and that will allow more calcium to circulate in the blood than a younger horse.
With 1 dose being missed allowing excess to clear over 24hrs is likely contributory to a better heart rate today.

I agree it sounds drastic episode of stress then clearance, yet would imagine over the course of excess calcium supplementation the older horse would have been showing slight symptoms, but as its at rest, it would be hard to see the lethargy, or be there to notice pee changes. Only when accumulation occurs would off-feed symptoms and other more noticeable symptoms arise. Op probably noticed not finishing off hay or eager for bowl feed.
Until the fateful ‘cup runneth over’ point episode of absolute lethargy, laying, no food interest, slow heart.
If this is added daily and the blood is daily dealing with a higher dose, just 1 day of not feeding the blood the excess, helps it clear.
I see excess happing slowly, like slowly filling up a cup….minor symptoms, then some more noticeable symptoms, then full cup = full-on issues./episode.

I also thought colic until low heart rate mentioned. With colic we usually have the stress hormones released from the autonomic nervous system yielding in most cases an elevated heart rate.

 

[JBM]

yes just to clarify this is Barry he is a 5yo tb and is doing light work but has a lot of days off
He has other issues but they’re related to his back and being treated as muscle related currently as the vet can’t find anything wrong but the physio can feel all this tight muscles
These issues are new tho and not sure if the back is related
I will be investigating it further with a blood test and checking kidneys and take it from there
We were due to do bloods anyway if his back wasn’t improving after back and core strengthening exercises

 

[JBM]

Appreciate all the theories and helpful advice and will keep updated when bloods return ??

 

[PurBee]

yes just to clarify this is Barry he is a 5yo tb and is doing light work but has a lot of days off
He has other issues but they’re related to his back and being treated as muscle related currently as the vet can’t find anything wrong but the physio can feel all this tight muscles
These issues are new tho and not sure if the back is related
I will be investigating it further with a blood test and checking kidneys and take it from there
We were due to do bloods anyway if his back wasn’t improving after back and core strengthening exercises

Ah ok - i now understand the confusion, and understand Dexter’s queries better.
I thought judy in the forest was your young one and you mentioned that the other horse you had couldnt be a companion due to issues which i took to relate to aging, (probably wrong!) so hence why Barry i thought to be your older one! (unless youve got an older 1 stabled aswell as barry?!)

Considering barry’s muscle issues (now i see why a calcium supplement was tried for tight muscles?…or did the muscle issues start after the supplement?)
Calcium excess generally causes muscle weakness, lack of performance. Calcium lack causes more behavioural excitability and heart flutters. Excess causes lethargy, lack of food interest.

It’s very common for high levels and deficiency symptoms of nutrients to have some overlapping symptoms, with other symptoms only attributable to excess or lack. As he’s been on this supplement, i find it hard to deduce it’s deficiency, so its definitely worth checking calcium/phosphate levels and if the vet easily offers it to check PTH (parathyroid hormone) levels.