Selenium - Tell me about it?

[diluteherd]

Someone has mentioned this to me as a possible cause for my mare's muscle problems.

So background on my mare is she is 8 years old, QHx and has had azatoria in the past (approx 2 years ago)

I have her on alpha a oil, top spec all in one, electrolytes and linseed oil. She is also on a medium sized haynet of haylage a night.

Its generally when we start working after a slight break she will show signs of cramping up and heavily sweating - this is just at walk.

Since putting her on electrolytes it seems to help, well I think, I havent really done any tests on her to see but we dont seem to suffer with muscle issues. But it would link in with my azatoria theory as it can be due to an imbalance of electrolytes and the fact I dont feed her any grains and pellets.

Ive been researching different reasons behind her problems, another option could be EPSM which is often seen in QH..

Anyway, its a bit of a ramble post without a decisive question in it, just wondered on others thoughts?

Many Thanks

 

[prettypony95]

my boy is a part bred Appaloosa who is prone to tying up. He is on a very low starch diet and I also feed him the NAF Vitamin E, Selenium & Lysine and also electrolytes and I have found that these have really helped, he tied up at the end of January and since he's been back in full work he has shown no signs at all of stiffness, cramping etc, even after having a week off work, as long as he has plenty of time to warm up gently and also to cool down in plenty of time.

 

[flintfootfilly]

Ooooooh, me, me, ME please!!!!

I now have a lever arch file full of stuff on selenium deficiencies, as I'm trying to prove that that is what is wrong with my gang of 6 Dales ponies so I've spent many hours looking up stuff on the internet and contacting vets with an interest in muscle stuff as well as some nutritionists.

I need to go out and feed my starving herd just now, but when I come back in I'll pop down a summary of what I know at the moment and the things that I think would be worth looking into.

But remember, I know nothing. I am just a horseowner who is desperately trying to find out what's wrong with my gang.

Oh, I love it when people are interested in selenium!!! Sorry to get excited. It's just that most folk don't seem to have much of a clue about it, or at least it seemed that way to me when I was asking lots of questions!

And the great thing about selenium deficiency if it IS that, is that some conditions are responsive to supplementary selenium, so there IS a treatment.

Sarah

 

[Oberon]

Article from The Horse today;

"Exertional rhabdomyolysis, otherwise known as "tying up," is a term used to describe a variety of muscle disorders in the equine athlete. Horses affected by tying up have varying degrees of muscle cramping or muscle soreness, with the more severe cases accompanied by elevated respiratory and heart rates, dark colored urine, and reluctance to move or stand.

A balanced diet, including vitamins and minerals, is just one factor in the treatment and prevention of tying up. Here are some ways that two specific nutrients, selenium and vitamin E, can help prevent or alleviate symptoms of tying up:

Selenium: During exercise several chemical processes occur, allowing the horse's muscle to utilize energy. However, those same processes produce oxidation-induced damage by free radicals. Selenium is a vital part of glutathione peroxidase--an enzyme that prevents free radicals from causing cellular damage. Deficiencies in selenium will directly relate to a decreased ability to rid the muscle of these detrimental substances.

Vitamin E (alpha-tocopherol): Most commonly found in green growing forage, vegetable oils, and synthetically in grains and supplements, vitamin E works in cooperation with selenium as a part of glutathione peroxidase. In addition, vitamin E is thought to play a role in cellular defense of free radicals by incorporating in cell membranes and preventing lipid peroxidation.

Selenium and vitamin E work together, and one cannot replace the other. Studies have shown that if there is a selenium deficiency, higher levels of vitamin E are needed. Conversely, if there is a vitamin E deficiency, more selenium will be needed. The optimum amounts of selenium and vitamin E required in this type of situation is significantly greater to prevent signs of damage.

Work with a veterinarian or equine nutritionist to ensure each horse is consuming adequate selenium and vitamin E in its diet. In the event a horse is deficient in either nutrient, work with a professional to select a supplement that provides the required vitamin E and selenium levels to keep the animal healthy.

Take Home Message

Selenium and vitamin E work together to prevent tissue damage from free radicals produced during exercise by the enzyme glutathione peroxidase and cellular membrane components. It's important to ensure the diet of performance horses is balanced for both vitamin E and selenium."

 

[flintfootfilly]

I found this review of equine muscle diseases by M Aleman really useful. There are a whole variety of muscle diseases which can present with some sort of tying-up whether it be a full scale refusal to move (with patchy sweating, dark brown urine, muscle tremors etc) or whether it is a more subtle work intolerance, general reluctance or what may appear to some as "stubbornness" or "laziness":

http://maquette.respe.net/system/files/documents_equine_muscle_disorders.pdf

If found that article a really good starting point to look at the long list of possibilities and see which ones I felt I could rule out, and which ones were more likely................ which included selenium deficiency (aka white muscle disease, white muscle disease, nutritional muscular dystrophy and a few other names too).

Then there's the university of Minnesota's neuromuscular website, which again is REALLY useful. Lots of pages on muscle disease that are worth looking at one there:

http://www.cvm.umn.edu/umec/lab/home.html

Perhaps the most relevant starting place on that site is the "decision-making tree" which is a flow chart of what order they suggest you carry out investigations:

http://www.cvm.umn.edu/umec/prod/groups/cvm/@pub/@cvm/documents/asset/cvm_88617.pdf

You'll see on that page that they suggest the hair or blood sample as being the starting point for quarter horses, and so it may be that you decide to check that out first, not least as it is cheap and easy to do (no need for a vet visit).

I had my gang hair-tested by this lab, Animal Genetics in Cornwall. It was £25 per pony, and I just had to send a few mane hairs, including the root, so the hair was pulled rather than cut. That would at least either confirm or rule out what they call "type 1 EPSM" also known as "type 1 PSSM", and sometimes called "type 1 PSSM so as to avoid upsetting anyone who refers to it as EPSM or PSSM! All the type 1's are the same gene mutation (GYS1), but when the names were first given, it was thought they were two different conditions, hence the two different names.

Animal Genetics (otherwise known as Avian Biotech) website is: http://www.avianbiotech.co.uk/horse-dna/EquineUK.pdf This link takes you to the submission form that you send in with your hair sample.

Anyway, after that............ thinking along the lines of selenium deficiency, this is briefly what I have found out so far, and I don't claim to know everything, so interested to hear what others have to say:

Worth having your grass, hay and/or haylage tested - a "forage analysis" and including trace elements in the analysis. Be sure to include selenium, even though this costs more.

I've had my forage tests done by Dodson & Horrell up til now. You can buy the forage test on their website:

http://www.dodsonandhorrell.com/fileadmin/user_upload/pdf/Dodson___Horrell_Forage_Analysis_Form.pdf

So I've always gone for proximate analysis plus "minerals B" which includes selenium.

Forageplus offer a similar service: http://www.forageplus.com/

When the analysis comes through, DON'T make the mistake I did, which was to assume that because it said selenium was "average" or "high", I thought that meant that it was ADEQUATE. This is absolutely NOT the case. It just means there was more in my sample than in many other samples they receive.

However, there was still only 0.04mg/kg or 0.05mg/kg selenium in my hay and my haylage. Even if my 500kg pony was eating 10kg hay a day (they get considerably less than that), that would only provide 0.4 or 0.5mg per day of selenium, which is only around HALF of the National Research Council (NRC)'s recommended intake of 1mg selenium per day for a 500kg horse.

If like me you are restricting intake, then the deficiency will be even greater.

So, if you KNOW you have a dietary deficiency, then you KNOW that you should address that. There are quite a few selenium supplements available, and they vary in the amount of selenium contained, as well as the FORM that the selenium takes.

Organic selenium (usually as selenium yeast) is considered more bio-available than inorganic yeast (sodium selenite or sodium selenate), so if your forage analysis shows a dietary deficiency, then it's worth searching out a supplement which uses selenium yeast.

If you are going to supplement selenium at all, you need to be ABSOLUTELY clear that selenium is beneficial in low levels but can be TOXIC and potentially FATAL at only about a 10 fold increase above normal levels. This leaves very little margin for error if you are weighing out or measuring out a supplement. BE SURE YOU DO YOUR SUMS RIGHT if you are going to supplement selenium. Don't kill your horse trying to make him better!!!

I've not found any vet in the UK who has experience of correcting a selenium deficiency by supplementation, and I've contacted the 3 vets who I think know the most about muscle problems in horses in the UK. So I've had to look further afield to published research on the internet.

This is the most useful paper I've come across in terms of deciding what level of supplementation to aim for:

http://jas.fass.org/content/87/1/167.full.pdf+html

It's an Italian paper (in English thankfully!) by Calamari, Ferrari and Bertin (fab names which is even better!!), and it really confirmed to me that IF I have a known dietary selenium deficiency, then I need to supplement at ABOVE the NRC general recommended intake of 1mg/day/500kg horse (but also being mindful to NEVER go above 5mg/day/500kg horse - that is the level NRC say it should NEVER be necessary to supplement above).

The above paper showed blood and plasma selenium increasing most rapidly when selenium (in the form of selenium yeast) was fed at 0.4mg/day, and so I decided to supplement at just below that level. I wanted to build in a little more leeway for inaccuracies in my measuring/weighing, and still be within a safe level of supplementation.

Selenium toxicity is not nice (understatement), so DON'T GO THERE!!! I keep reminding myself of that, and double-checking any weighing I do.

This paper also shows that it takes a while for blood and plasma selenium levels to increase. It takes even longer for muscle and liver selenium levels to increase, so supplementation at a higher level MAY have to be carried out for quite a few months. I have not been able to find a vet in the UK with any experience of that, so again I'm just going by what I've found on the net.

Just going to post this now, rather than risk losing all I've typed! Will add more if I can edit this post, or add a new reply..........

 

[flintfootfilly]

This paper also shows that it takes a while for blood and plasma selenium levels to increase. It takes even longer for muscle and liver selenium levels to increase, so supplementation at a higher level MAY have to be carried out for quite a few months. I have not been able to find a vet in the UK with any experience of that, so again I'm just going by what I've found on the net.

The guideline I've come across for replenishing selenium in whole blood is that most of the selenium in blood is contained in an enzyme called glutathione peroxidase (which is abbreviated to GSH-px). GSH-px is found mainly in the red blood cells, and is incorporated into them as they are generated. Red blood cells have a life expectancy of around 5 months, so it will take up to 5 months to replace a complete cycle of selenium-deficient red blood cells (RBCs) with RBCs which have a good level of selenium (as GSH-px).

So for my gang, I'm looking at supplementing at this high level for 5 months and then review how we're doing. I'm having to kind of make it up as I go along because I just can find no-one who's dealt with what I believe is a chronic selenium deficiency in this way (and I could be right or I could be wrong!

Now, because selenium is ESSENTIAL and yet HIGHLY TOXIC, and because I feel a bit on my own with this one, I've chosen to have monthly blood tests on my gang to check their muscle enzymes (opting for a comprehensive profile to include those) and also to include vitamin E and GSH-px as an indicator of selenium. This doesn't come cheap. The comprehensive test works out as around £70, and then the vitamin E and GSH-px is a further £70 or so......... but I really am very aware that if I get this wrong, my ponies could be dead, so I have to be guided by how my ponies appear and also by how the bloods change, so for me, it's worth it.

If you elect to have comprehensive blood tests and vitamin E and selenium bloods taken, then there are a few other things it's worth considering:

Oh, I probably should have said right at the start that it's worth doing a comprehensive blood test early on, making sure it's a true RESTING blood, ie that your horse is at home, has not worked that day or possibly even the day before, not done anything strenuous for at least a good few days, and look at the muscle enzyme levels AST, CK (especially), and LDH. Ask for a copy of the complete blood report so you can look at it thoroughly and check levels for yourself.

World experts like Beth Valentine (the EPSM in draft horses "guru"), Stephanie Valberg (the PSSM vet and co-inventor of the genetic test for type 1 PSSM and Sue Dyson all quote 350 as being their "high normal" for CK. Anything above that (in a true resting blood) is not considered normal. Some vets are used to seeing full scale tie-ups in which CK can rise into hundreds of thousands, so may be dismissive of a CK of mid hundreds to low thousands, and this is absoluely why it's worth having a copy of the report yourself. Also, you are the best person to have quick access to compare consecutive blood test results.

I understand that a blood test is quite a good indicator of vitamin E status.

With blood testing for selenium, it seems that tests seem to test more often for GSH-px as and indicator of selenium, rather than for selenium itself. If you opt to have GSH-px tested, then do ask for it to be done on WHOLE BLOOD rather than plasma or serum. My understanding is that testing whole blood gives a better indication of the long term selenium status (reflecting the fact that the selenium is contained largely in the red blood cells which are replaced every 5 months or so), whereas plasma selenium will only give you a short term picture and gives no idea of the longer history of selenium levels.

One other thing with GSH-px levels is that you will probably be quoted 30-150 as being the reference range for horses. In other words this is the range into which 95% of "normal" horses would fall.

I have come across at least 3 things which cause me to DISBELIEVE the accuracy of that reference range:

Firstly, this paper by (the late) Helen Fullerton, who was a lecturer in soil science at Glasgow university for 12 years. This paper is suggesting selenium supplementation of cattle to increase their resistance to bovine TB. Its relevance for me was that it strongly questions the reference range for GSH-px in cattle, believing it to be too low, and therefore highlighting some cattle whose levels are TRULY too low to be classed as having an "adequate" level. It seems that the reference range is not appropriate for picking up selenium-responsive conditions - ie those conditions which WILL improve given selenium supplementation (for example retention of afterbirths), and appears to begeared more towards picking up disease which is much more immediately life-threatening.

So if your GSH-px blood comes back as "within reference range" then you may, or may not, choose to question whether you believe that or not!

Here's the paper, which went to Parliament's Agriculture committee in 2004:

 

[flintfootfilly]

Sorry, I meant 1999. This is Appendix 29 to the Select Committee on Agriculture. By Helen Fullerton, relating to suggesting selenium supplementation to reduce bovine TB:

http://www.publications.parliament.uk/pa/cm199899/cmselect/cmagric/233/233app30.htm

As it wasn't possible to speak direct to Helen Fullerton as she died a few years ago, I contacted Danny Goodwin Jones who is mentioned in the above report as running a Trace Element supply business in Wales. I wanted to ask him if there had been any progress in GSH-px reference levels changing, and whether he still felt that the current levels were missing selenium-responsive conditions. No progress in changes. Raising selenium status is still seeing improvements in livestock. Farmers continuing to be happy to supplement to reduce the selenium-responsive conditions.

Two of my gang have come back as being within GSH-px reference levels (of 30-150 U GSH-px /ml PCV (their actual results were 58.3 and 71.7), and yet I have accumulated quite a list of things that point to potential selenium deficiency. I have to add that I have not found a vet who has come across the work intolerance signs that I'm seeing as being associated with selenium deficiency. I guess I'm just not willing to believe that white muscle disease is all or nothing. I believe there WILL be shades of grey, and that other owners WILL be seeing that in their animals, but may not be aware what it is. I may be right or I may be wrong. I don't have any better suggestions to follow up right now.

Like I say, I have a list of things which point to a potential selenium deficiency. I may be right or I may be wrong. At least I'm trying to find out what's wrong and address it is possible. Signs which my gang have include:

- all 6 ponies are showing some elevated muscle enzymes and work intolerance, to varying degrees.
Although some are closely related, they are not all closely related, and I’ve not been able to find anyone else with Dales ponies who is coming across problems on this scale

- Would fit with their exercise intolerance

- A detailed look at my hay analysis shows selenium levels of only 0.05mg/kg selenium which means that Max’s daily ration contains only 0.34mg selenium (compared to NRC’s recommended daily ration of 1.0mg selenium), so it is quite possible that a deficiency has built up over the years. Various papers refer to similar levels in hay as being deficient.

- Although I have sometimes fed a feed balancer, it has been intermittently, and only at a reduced rate, which I now realise contains only 0.3mg selenium, so still keeping the daily ration below NRC’s recommendation

- Out of the 3 different mares who have had foals here, all 3 have had retained placentas, and I now realise there is a recognised link between selenium deficiency and retained placentas in various species, and have also come across one paper showing how selenium supplementation reduced the retention time of placentas in draft mares

- One of my mares had 2 other foals when she was owned by a friend of mine at the time. Dora did not retain her placenta on either of those foalings. Interestingly, that friend has bred 8 Dales foals, and had no retained placentas. Not statistically significant, I’m sure, but interesting nonetheless.

- Red cell count is low in Max, Megz and Rock (can be associated with selenium deficiency, allowing more damage by oxidative stress, resulting in early removal of cells from the blood)

- MCV is close to top end of normal in Fox, Max, Megz and Rose (which could maybe be because of more young cells in circulation, as a result of the older cells being damaged and removed early)

- It may be possible that Megz’s ongong excess salivation could be accounted for by selenium deficiency (Se deficiency known to cause problems with masticatory muscles and to cause dysphagia)

So, not conclusive, but LOTS of interesting stuff!

Since I drew up that list, I've also realised that the small patch of fibrotic myopathy found in one of my girl's hamstring can be found as a consequence of nutritional myopathy......... obviously there can be other causes too, but hmmmmmm how many signs does a pony need to have before anyone will feel confident to say it's caused by selenium deficiency??

Again, not in horses, but another paper caused me to think that perhaps the reference range is set too low at present to include selenium-responsive conditions. It was one looking at supplementation with selenium, copper and one other element in lambs, and showed that quality was responsive to selenium even when the original blood selenium levels were at a level considered adequate. Sorry, can't find the reference to it just now, but it was something else that made me believe that the current reference levels really aren't geared to picking up more subtle conditions.

Right, I think that's me just about done for now!! I should say I was originally looking into the cause of work intolerance in just one pony, and it was only when I realised the others were showing more subtle signs that I started to look for a possible common cause and that's when selenium came to the fore.

Whatever's wrong with your horse, I hope you get to the bottom of it and can find a good way forward.

Sarah

 

[flintfootfilly]

Ah, one more thing VERY BRIEFLY!!! (honest). One of the nutritionists I spoke to said they are seeing quite a lot of good doer / native types who are "overfed but undernourished". Apparently it's a term used in humans too.

It's very easy to feed too many calories, but not get the balance, quantities and ratios of all the minerals correct too.

.... and I think this is largely what's happened with my gang, although even if they weren't on restricted rations, their dietary intake of selenium would have been only half what it should be each day. With their restricted ration, it's about a third of what it should be. So this has totally brought home to me how important it is to feed a balancer which closely matches the needs identified by a grass/hay/haylage analysis. Most balancers I've come across don't seem to provide anywhere near the levels of the various minerals that my forage requires (going by NRC recommendations).

Sarah