Vitamin K for Horses

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What is vitamin K?

The name ‘Vitamin K’ refers to a group of fat soluble vitamins that include:

  • Vitamin K1 (phylloquinone): found in fresh green plants
  • Vitamin K2 (menaquinone): produced by bacteria. There are 15 different menaquinones
  • Vitamin K3 (menadione): synthetic vitamin K

What does vitamin K do?

Vitamin K is required for many functions in the body. The most important of these are:

  1. Activation of blood clotting mechanisms
  2. Maintaining vascular health; and
  3. Healthy bone metabolism

How much vitamin K does a horse need?

The true requirement for vitamin K in horses is still unknown. Primary vitamin K deficiency (i.e. nutritional deficiency not caused by a vitamin K antagonist) has never been recorded in a horse.

Published information suggests that the absorption of vitamin K from fresh forages and absorption of vitamin K produced by bacteria in the gut is enough to meet requirement. However, recent studies have called into question the ability of a horse to absorb bacterial derived vitamin K2 from the hindgut1. Still, there are many bacteria in a horse’s small intestine and vitamin K is definitely able to be absorbed from there.

However, horses in stable conditions without access to fresh green forage may not receive optimal amounts of vitamin K in their diets. In these situations, some supplementation may be required.

What form of vitamin K is best?

There has been some debate in recent times regarding which form of vitamin K is best to supplement with. In horses, it appears that most forms of vitamin K are suitable for supplementation.

A study in horses published in the Journal of Animal Science (Terachi et al 2011)2 found that supplementation with Vitamin K3 (the form most commonly used in horse feeds) was the most effective at increasing blood concentrations of the biologically active menaquinone, MK-4.

A more recent study3 has suggested that vitamin K3 is not converted to MK-4. However this study used a single dose of vitamin K3, with blood samples only taken for 8 hours post-dosing. This is in contrast to the Terachi et al. study which supplemented horses for 7 days and found the highest levels of MK-4 in the vitamin K3 supplemented horses. It is likely that in the study of Skinner et al, the single dose of Vitamin K3 and the short time-frame for blood sampling may not have allowed enough substrate or time for conversion to MK4 to occur.

Vitamin K3 has been demonstrated to be converted to biologically active MK-4 in multiple animal species and it would appear horses are no exception.

  1. Skinner JE, Cawdell-Smith AJ, Regtop HL, et al. 59 Extent of vitamin K absorption from the equine hindgut. Journal of Equine Veterinary Science;35:409.
  2. Terachi T, Inoue Y, Ashihara N, et al. Plasma vitamin K concentration in horses supplemented with several vitamin K homologs. J Anim Sci 2011;89:1056-1061.
  3. Skinner JE, Cawdell-Smith AJ, Biffen JR, et al. 11 Intestinal absorption of different vitamin K compounds in the horse. Journal of Equine Veterinary Science;35:387.

Meet The Author: Dr Nerida McGilchrist


Dr Nerida McGilchrist is FeedXL’s co-founder and equine nutrition specialist. She holds a degree in Rural Science, a doctorate degree in equine nutrition and nearly 20 years of full time, on the ground experience in feeding all types of horses. To learn more about Nerida and to ‘meet’ the rest of the FeedXL team, check out our About Us page here.

 

 

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Choosing a Quality Electrolyte for Your Horse

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I don’t know if you have noticed, but there are LOTS of different electrolyte supplements on the market! Pastes, powders, liquids – and they are all so different… making it really hard to know which ones are best.

The job of an electrolyte supplement is to replace the electrolytes lost in your horse’s sweat… namely sodium, chloride and potassium (the three major ones) as well as magnesium and calcium.

Quick Tip: Forages are usually high in potassium. So when your horse is being fed a forage based diet, there is normally plenty of potassium in the diet to meet requirements during normal training periods. Which means the two main electrolytes your horse needs added to the diet are sodium and chloride. And together, these electrolytes are ordinary table salt… so topping up electrolytes is often as simple and inexpensive as adding salt to your horse’s diet!


For an electrolyte to do a good job of replacing the electrolyte minerals your horse loses when sweating, it should be at least 80% ‘salts’ and 20% or less glucose or other base or filler.

Specifically, these high quality products should be 20 – 25% sodium, 43 – 48% chloride, 10 – 12% potassium and also have smaller amounts of magnesium and calcium (normally 1 to 2%).

If you put one of these high quality products into FeedXL, for a 450 kg (990 lb) horse in very heavy work, at a dose of 60 grams per day, this is how it should look (with JUST it in the diet):

High Quality Electrolyte

This product is 22.5% sodium, 45.1% chloride, 12.1% potassium, 1% magnesium and 1.5% calcium.

To give you a comparison, here is another product, also added in FeedXL at a 60 gram dose for a 450 kg (990 lb) horse in Very Heavy Work … look how much less mineral you are getting at the same dose rate!

Low Quality Electrolyte

If the mineral levels are much lower like this, you’re probably paying a lot for a lot of filler and it might be time to consider a new supplement!

It can be a little tricky to read labels because everyone presents their label information a little differently (just to keep us on our toes!)… so if you want to check how good your electrolyte is, create a diet in FeedXL like this, for a 450 kg (990 lb) horse in Very Heavy Work, add 60 grams of your chosen electrolyte and see how it compares to these ones… the one at the top being good, the one at the bottom being a waste of money!

We hope that helps you to find the best electrolyte supplements! If you haven’t yet got started with FeedXL you can join us here.

P.S. Be really careful not to overfeed salt and electrolytes because they will make your horse’s feed taste yuk and your horse will stop eating. If your horse is not eating well, try reducing or even for a short period removing any salt or electrolyte from the feed and see if this helps. For more on keeping your horse eating, you can read this post.

 

 

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Horse standing in field

Why isn’t Sulfur included in FeedXL?

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Sulfur is a critical part of all proteins and horses need it to create protein, particularly the protein of their hooves and hair!

If it’s so important, why isn’t it included in FeedXL you might ask?!

We don’t include sulfur in FeedXL because the chance of a deficiency is virtually zero. Forages contain enough sulfur, so that even if intake was reduced to just 1% of bodyweight, maintenance reuirements would still be met.

My texts suggest possibly that straw based diets could become sulfur deficient, but as long as you use FeedXL to make sure protein requirement is met, the assumption is that sulfur requirement will also be met.

 

 

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Vitamin B12 – Do horses need it in their diet?

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Here is something (nerdily) interesting… the molecular formula for Vitamin B12. It is the ‘biggest’ of all of the vitamins and yet required in the diet in the smallest amounts.

It contains the mineral cobalt which constitutes somewhere around 5% of its weight.

The only reason a horse needs cobalt in its diet is to allow their gut bacteria to produce Vitamin B12!

Researchers currently don’t know how much vitamin B12 a horse needs.

And… it appears that natural levels of cobalt present in forages and other feedstuffs is enough to meet a horse’s cobalt and therefore Vitamin B12 requirement.

It is important to keep in mind however that a horse’s gut bacteria population needs to be healthy if your horse is going to have the capacity to produce enough B12.

Your horse’s diet is going to determine how well the gut bacteria can make vitamin B12 for your horse. In cattle, it has been shown that a high forage diet supported the production of 3 times more vitamin B12 than a high starch diet!

Loss of appetite is one symptom of a vitamin B12 deficiency. Fatigue and poor performance will also occur when a horse is B12 deficient.

Horses receiving adequate cobalt (which it appears they should do just from their forages) AND with a healthy hindgut, shouldn’t need additional vitamin B12 in their diet.

For information on how you can keep your horse’s hindgut healthy (and therefore vitamin B12 production at a maximum) see our article Keeping The Hindgut Healthy.

 

 

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What are the Symptoms of Mineral Deficiency in Horses?

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“What symptoms would I see if my horse was mineral deficient?” ‘Anita’ asks me.

My answer…

“That’s a really good question”… the actual answer is the reason why so many of us don’t have ‘problems’ with our horses, we have ‘disasters’!

One of the things I love about being out and about at horse events is having real conversations with ‘real’ horse people about nutrition. I can sometimes forget that what is obvious to me is often not so obvious to others. So these types of questions really make me stop and focus on things from YOUR perspective.

Anita’s question was particularly brilliant because it highlights one of the HUGE issues in horse nutrition. And that is that ‘chronic long-term mineral deficiencies’ tend to go UNNOTICED until something truly goes horribly wrong.

The best analogy I can give you is it is like white ants… often the presence of white ants goes unnoticed until they have done so much damage to the structure of a building that things literally start to fall apart. Once you can SEE the damage, the issue is serious.

It’s like this with minerals (and vitamins) for horses. Once you can SEE a mineral deficiency, you can be sure that issue has been there for a long time and that the damage is now extensive.

Which means…

Just because you CAN’T SEE a mineral deficiency doesn’t mean one doesn’t exist.

And in fact if you are not supplementing your horse correctly, either with carefully chosen fortified feeds or vitamin/minerals supplements I would say with 99.9% certainty that your horse will be deficient in something that will eventually cause a health issue.

And here is the thing… all of these nutrition related deficiency issues are so easily avoided. Instead of spending several months (and often several thousand dollars) fixing the problems caused by deficiency… you can just prevent the deficiency and therefore prevent the issue.

Let me answer Anita’s question a bit more first, and then I’ll come back to how you can prevent the problems!

Here are some symptoms of mineral (and vitamin) deficiency…

And remember these are symptoms of LONG TERM deficiency, they tend to take several months to several years to show up… listed in no particular order:

  • Dull coat that lacks shine and richness of colour
  • Cracked, weak hooves-Joints that start to deteriorate at a young age
  • Poor immune response, taking a long time to recover from immune challenges
  • Changes in behaviour, often toward more anxious, spooky behaviour
  • Loss of muscle or inability to gain muscle
  • Weight loss or inability to gain weight
  • Low energy or reaching fatigue earlier than they should for their level of fitness
  • Gut issues, including poor digestion, poor absorption and an increased risk of gastric ulcers
  • Uterine artery rupture in foaling mares
  • Flexure limb deformity and OCD in foals and young horses
  • Stillbirths
  • Broken bones including legs, ribs, pelvis (unfortunately often the first symptom that is recognised in chronically calcium deficient horses)

This list could go on (and on, and on) but this will cover many of the issues many of you will see.

Unfortunately we also often try to treat the symptom before we treat the underlying cause. So good nutrition must (ALWAYS) go hand in hand with any treatments given to these horses. For example it’s virtually no use using a joint supplement when a diet is chronically copper and zinc deficient.

So I guess what I really want to convey here is that EVERY horse’s diet, almost without exception, needs some sort of vitamin and mineral support. And if they don’t receive that support, one (if you are lucky) or many of these issues will start to show in your horse.

And this is where FeedXL comes in… FeedXL helps you figure out exactly which vitamins and minerals are missing from the diet, and exactly which feeds or supplements (of the literally thousands of options you have) can be used to best meet those needs.

AND it stops us doing that thing where we overfeed or oversupplement Just. In. Case. Which at best leads to wasting money. At worst ends in equally disastrous vitamin or mineral toxicity.

The moral of the story? Just because you can’t see a problem doesn’t mean there isn’t a problem!

The sooner you look at your horse’s diet and fix any vitamin or mineral deficiencies, the better!

New to FeedXL? Click here to learn more about our horse nutrition calculator and start your free trial today.
 

 

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Magnesium Oxide for Horses

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Magnesium oxide. It’s one of those ingredients people love to disagree over, should we use it, shouldn’t we use it, is it bioavailable or not for horses??

Part of this contention is due to the fact that magnesium oxide is a created ingredient… it is cooked in a process called calcination, that reacts magnesite with oxygen to create magnesium oxide.

Like all things, it can be made well, or it can be made poorly, and this then impacts on whether it will be bioavailable or not. So it’s not like limestone (calcium carbonate) that is mined for example and is generally always the same.

So when reading about magnesium oxide for horses, keep in mind that most studies do not report the conditions under which it was manufactured OR its final particle size, both of which have a huge impact on final bioavailability.

I still believe that quality magnesium oxide is a very useful source of magnesium for horses, but then I am very fussy when it comes to where it comes from and how it is produced!

We have information on various sources of magnesium for anyone who would like to read some more here: https://feedxl.com/36-which-form-of-magnesium-is-best/

And for anyone who loves details, this is a now old but still informative paper on this subject (Beede et al 1992). It is a Dairy paper but talks in detail about factors affecting magnesium oxide bioavailability: https://animal.ifas.ufl.edu/apps/dairymedia/dpc/1992/Beede.pdf

 

 

Do you have a question or comment? Do you need help with feeding?

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Iron: Is There a Link to Laminitis?

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Dietary iron is thought by some to contribute to the incidence of laminitis in horses, with serum ferritin starting to be used as the measure of iron status.

I (Nerida) don’t know if this is the case, but in reading human literature, it seems the relationship between serum ferritin and inflammation is a bit of a case of chicken or the egg. Lots of information shows serum ferritin is elevated in humans with inflammatory disease and/or metabolic syndrome, but it is not clear what happened first; did serum ferritin rise and cause inflammation, or did inflammation and cell damage occur and cause elevated serum ferritin?

So I thought a good place to start is with a link for you to a review on serum ferritin. This article tells us that serum ferritin is actually a little protein ball, with a hollow centre (my words) where it keeps iron. Depending on how much iron is available in the body, the amount of iron inside the ferritin can vary a lot.

When serum ferritin is measured, it is the protein that is being measured, not the iron. So a serum ferritin measure tells you how many little protein balls are there but not how much iron they actually contain.

The other interesting thing to note is that ferritin is made within cells and is not made in the blood. So it seems that for ferritin to get into the blood it has to come out of the body’s cells (with very limited evidence if any, according to these authors, of any regulated ferritin secretion mechanism in mammals). This leads to the hypothesis that the elevated serum ferritin seen during inflammation is due to leakage from damaged cells into the blood.

The paper goes on to talk about the relationship between serum ferritin and liver iron stores, which are considered the gold standard for assessing body iron stores. While serum ferritin is usually related to liver iron in ‘normal humans’ that don’t have inflammatory disease, serum ferritin can both under and over-estimate liver iron stores where some form of inflammatory disease is at play.

Meaning it is not necessarily a good indicator of overall iron status. These authors suggest serum (‘soluble’) transferrin receptor (sTfR) as being much more useful.

Anyway, there is a lot to take in and I have only had one read over and would need to read it many times to fully appreciate all of the content. The simple point I want you to take away is that serum ferritin is not necessarily an indicator of iron overload from high dietary iron and may instead be an indicator of inflammation. Maybe the chicken came first… or was it the egg??

I’ll keep reviewing papers over the next several months! 

Here’s a direct link to the article mentioned above: https://pubs.rsc.org/en/Content/ArticleLanding/2014/MT/C3MT00347G

 

 

Do you have a question or comment? Do you need help with feeding?

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Iron for Horses: Could Forage Be Enough?

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Comparison of equine dietary iron requirements to iron concentrations of 5,837 hay samples

N. Richards and B.D. Nielsen, 2018

Introduction

Iron is essential for the production of red blood cells. According to the 2007 Horse NRC, Fe requirements are 50 ppm for growing foals, lactating and pregnant mares, and 40 ppm for all other classes of horses. The 2005 NRC suggested a maximum tolerable Fe concentration of 500 ppm using data from other species. It is claimed that excess dietary Fe is causative of horses becoming insulin resistant.

Athletic horses, and particularly those in Thoroughbred racing, are often supplemented with Fe in an attempt to improve performance. Supplementation is commonly carried out without any formal analysis of the diet to determine if additional iron is required. Forages are typically high in iron and supply a majority of iron in all equine diets.

This study looks at the iron concentration in forages typically fed to equines and whether iron from forage is enough to meet the iron requirement of an athletic horse.

Methods

Nutrient concentrations from hay samples submitted for analysis in 2017 and for which Fe was measured were obtained from Equi-Analytical, representing 3,060 grass, 1,193 legume, and 1,584 mixed hay samples.

Iron concentration was measured using inductively-coupled plasma mass spectrometry (ICP). Analysis methodology is available from dairyone.com Statistical analysis was performed using Proc MEANS of SAS.

Results

Iron was highest in Legume and Mixed Mainly Legume Hays and lowest in Grass Hay (Table 1). All hay types had a mean iron concentration more than five times that required by athletic horses and a median iron concentration more than three times.

From all hay samples (n = 5,837), 707 contained Fe at or above the suggested tolerable threshold of 500 ppm, while only 81 contained Fe at less than 50 ppm. Further, only 15 contained Fe at less than 40 ppm.

Discussion

A 500 kg horse in heavy work has an iron requirement of 500 mg/day (NRC 2007; based on a daily feed intake of 2.5% bodyweight and a requirement of 40 ppm). Forage intake is often restricted by Thoroughbred trainers. But even when fed at 1% of bodyweight to a 500 kg horse, these hays will supply an average 1,060 mg to 2,230 mg of iron per day, supplying more than 200% of daily iron requirements in the forage component of the diet alone.

Fortified grain concentrates are fed at an average 2.5 kg/horse per day in Australian Thoroughbred racing stables (Richards 2003). These concentrates have an average iron concentration of 190 ppm (FeedXL.com), adding an additional 475 mg/day of iron to the diet of these horses. Almost 60% of Australian Thoroughbred trainers then add an iron supplement to their horses’ diets (Richards 2003). It is expected similar trends would be found in the USA.

Based on this broad diet analysis, forage is able to meet the daily iron requirement of athletic horses. When iron from fortified feeds and supplements is added, there would be few racehorses receiving less than 300% of their daily iron requirement. It’s not unexpected that many horses would be receiving in excess of 500% of their daily iron requirement

What About Insulin Resistance

Given the dearth of Thoroughbred racehorses that are insulin resistant, despite Fe supplementation in combination with diets that can easily supply amounts beyond requirements, it seems unlikely excess Fe causes insulin resistance. However, it is recognized insulin resistant horses may have elevated serum ferritin.

References

Council NR. Nutrient Requirements of Horses: Sixth Revised Edition. Washington, DC: The National Academies Press, 2007.

Richards N, Hinch G, Rowe J. The effect of current grain feeding practices on hindgut starch fermentation and acidosis in the Australian racing Thoroughbred. Aust Vet J 2006;84:402-407.

FeedXL Nutrition Software, https://feedxl.com/, 2018.

HUGE THANKS to Equi-Analytical for providing the data to write this paper, which was presented as a poster at the recent International Conference on Equine Exercise Physiology (ICEEP).

 

 

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What You Should Know About Phosphorus and Phytate

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Horses are unique because they absorb phosphorus from their hindgut… which is a stroke of genius on a horse’s part… here is why.

Phosphorus in grains, legumes/oilseeds is bound up in a compound called phytate. ‘Phytate bound phosphorus’ is as good as indigestible for most monogastrics who absorb phosphorus from their small intestine (like pigs and poultry).

But horses enlist the help of their oh so useful hindgut bacteria to break down the phytate for them and release the phosphorus for absorption! Clever!!

So if you ever read statements about specific ingredients like soybean meal containing indigestible phosphorus because they contain phytate, think two things:

1. ALL grains and legumes/oilseeds contain phytate; and
2. Horses have got a useful arrangement with bacteria and a different site of absorption (their hindgut) that allows them to access the phosphorus.

It’s a very well designed aspect of the horse’s gastrointestinal tract!!

 

 

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Vitamin C for Horses?

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Did you know Vitamin C is not an essential nutrient in your horse’s diet?

Unlike we humans, who will get scurvy and die if we don’t eat vitamin C, horses make their own vitamin C in their liver!

Clever right!!

There are some situations, like when a horse is very ill, really stressed or has liver damage where supplementing with vitamin C may be useful.

Just be mindful that when you want to stop supplementing you should remove the vitamin C from the diet gradually so the horse has a chance to ramp its own production up again.

 

 

Do you have a question or comment? Do you need help with feeding?

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