Herbs: Where Do They Fit in Your Horse’s Diet?

The use of herbs as a source of compounds beneficial in promoting good health dates back many (many) thousands of years. In the age before ‘synthetic’ drugs, herbs were the only available source of potentially health-enhancing compounds and as such, they were used extensively. But where do herbs fit in a horse’s diet?

With modern day medicine now able to reliably reproduce the specific chemical components of plants that have the desired biological effect, herbs are not so prominent in the treatment or prevention of disease. Herbs are however still enormously popular both in human and equine diets. This newsletter is going to look, in a very broad sense, at how herbs are and perhaps should be used for equines.

‘Herbs are medicine’

The true and traditional role of herbs is to provide biologically active ‘medicines’ to treat or prevent disease states. I am the first to confess I know little about the use of herbs as medicine. A true understanding of how to use herbs effectively to treat or prevent certain diseases requires a full understanding of disease pathophysiology and the chemical actions of the herbs themselves. To understand all of this fully would take many years of committed study.

Herbs can certainly play a valuable role in the treatment or prevention of disease when used together with conventional or complementary medicine, but to use them effectively, they must be used correctly. Discuss the use of herbs or herbal preparations with your trained herbalist and ALWAYS include your veterinarian in these discussions. Quite a few herbs can have interactions with traditional medicines which if not fully explored can result in negative consequences. For example, ginger has been shown to increase bleeding time, so if it was used in conjunction with other anti-clotting drugs or if your vet was unaware your horse was being supplemented with ginger prior to undertaking surgery there may be complications with excessive bleeding.

Natural doesn’t necessarily mean safe

It is common for people to mistakenly believe that because herbs are natural, they are also completely safe. Because herbs contain drug-like components, many of them have the ability to become toxic if fed in too large an amount. Because a horse is such a large animal, the risk is, in reality, probably quite small, but you should always investigate potential toxicity for any herb you are considering to use. Garlic is a good example of a herb that, if fed in too large an amount can have negative consequences, with severe anaemia possible in this case.

Some herbs also accumulate high concentrations of certain minerals, with many plants being selenium accumulators and seaweed or kelp a good example of a group of plants that accumulate potentially toxic levels of iodine.

Additionally, even though some herbs can have positive effects, like nearly every modern medicine available, many also have the potential to cause negative side effects. Ginger, for example, has been shown to reduce post-exercise recovery time, but it is known to cause gastric ulcers in humans (presumably if it is taken regularly or in large doses) and is theorised to do the same in horses.

Herbs as nutritional supplements

Many herbal preparations are sold today as ‘complete nutritional supplements’ and yet are sold without any form of typical analysis to support the claim that they are providing a complete range of nutrients that the horse needs in its diet. Herbs are also used singularly to provide vitamins and minerals to a horse’s diet, but in very few cases are herbs actually able to provide enough of any nutrient to have an impact on your horse’s overall nutrient intake.

Herbs are just plants, and with the exception of selenium accumulating plants, seaweed which accumulates iodine, and perhaps rosehips as a source of vitamin C, herbs really aren’t capable of providing significant amounts of vitamins or minerals in a diet.

For example, garlic is commonly fed as a source of copper and selenium. While garlic does contain copper and selenium, horses are so large and the typical dose of garlic so small that adding garlic to a diet has no real impact on the diet. The table below shows the daily contribution of 250 grams of garlic (a massive dose and one that researchers at the University of Guelph, Canada observed to cause anaemia) to the diet of a 500 kg horse in moderate work (shown as percent of Recommended Daily Intake or RDI):

Nutrient % RDI supplied by 250 g/day dried garlic
Calcium 2.8
Phosphorous 3.25
Copper 1
Zinc 1.5
Selenium 2.75
Manganese 2
Iodine 0.0
Iron 1.5

Enter any herb we have in the FeedXL database to your diet and you will see that even in large doses they have little to no useful impact on the nutrient content of a diet.

That is not to say all herbal preparations are not worthwhile. Some well trained herbalists with a good understanding of nutrition have nutritional supplements that contain herbs together with more conventional sources of nutrients to give you supplements that do contain useful levels of vitamins and minerals together with complementary support from the herbs.

If you are buying herbal supplements that are being sold as nutritional supplements ALWAYS request a typical analysis. If one is not available, you should question how the supplier knows it is a nutritional supplement if they can’t even tell you what nutrients it contains. Don’t spend your hard-earned money on supplements that promise a lot without any sort of evidence to back it up.

Balanced diets, best results

As always, a balanced diet should underpin your horse’s entire health regime. While the use of herbs can certainly help support and promote good health or assist in the treatment of disease, if you are feeding herbs on top of diets that contain deficiencies of critical vitamins or minerals their effectiveness will be severely limited. Using FeedXL to first balance your horse’s diet, then working with your trained herbalist to devise a herbal strategy specifically for your horse will give you the best results.

Spice it up!

Herbs can certainly play a valuable role in maintaining or promoting the health of your horse. If you wish to use herbs as part of your horse’s routine health plan, you should keep the following in mind:

  • Use herbs only from trusted suppliers that can guarantee the consistent quality of the herbs.
  • Always discuss the use of herbs with your vet, particularly if your vet is also prescribing modern medicines for the treatment of a particular condition.
  • Understand the herbs you are using, particularly their potential toxicities so that you can use them to good effect without having them cause their own problems.
  • Don’t forget that very few herbs contain nutrients in high enough concentration to contribute substantially to any horse’s diet. If you are buying herbs as nutritional supplements always request a typical analysis for the product.
  • If you are using herbs like seaweed to provide a particular nutrient, always use FeedXL to calculate accurate dose rates to avoid overfeeding and creation of nutrient toxicity.

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.



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

We would love to welcome you to our FeedXL Horse Nutrition Facebook Group. Ask questions and have them answered by PhD and Masters qualified equine nutritionists and spend time with like-minded horse owners. It’s free!

Click here to join the FeedXL Horse Nutrition Facebook Group


How to Choose a High Quality Horse Feed

With literally hundreds of feeds available for all of us to choose from for our horses the choice can be a bit overwhelming. While FeedXL is a brilliant tool in helping you see which feeds deliver the nutrients your horse needs and which don’t, what FeedXL can’t help you with is determining the actual quality of the feed. Nutrient profile and balance is one thing, but the ingredients used to make the feed are another thing entirely, and it is this aspect of feeding that you need to stay fully in control of.

Things like the ingredients used to make a feed, the quality of protein in the feed, whether the feed is made to the same recipe or made using least cost batching methods, how it is processed and the facility it is made in all contribute to determining a feed’s quality. These aspects of feed quality are discussed in more detail below.

Ingredients Used

When considering purchasing a feed have a look at the ingredients listed on the bag or label. First major rule is, if there are no ingredients listed, don’t buy the feed. This is not common but it does happen. If you have no idea what is in the feed then do not put it in your horse’s mouth.

The ingredients list will give you a good indication of whether the feed is a high quality feed or not. When looking at an ingredient list you should take note of the actual ingredients used and the number of macro ingredients (the grains, pulses and oilseeds) used. Higher quality feeds will use more ‘whole’ ingredients like corn, barley, wheat, oats, rice, full fat soybeans, sunflower seeds, faba or field beans, lupins (if you are in a part of the world that uses lupins for horses) and linseed or flax and they will contain a big variety of ingredients. When I say ‘whole’, it doesn’t mean they are in the feed in a whole form, just that the entire ingredient is used in the feed and not just a part or a by-product of it. Higher quality feeds will also list the specific oils they use if any. Lower quality feeds will list more generic or lesser quality ingredients like protein meals, pollard and bran (which can come under many names including wheat midds, middlings, broll, millrun and millmix), cottonseed meal and unnamed vegetable oils and there will often be less than 5 macro ingredients used.

Determining feed quality just from an ingredient list isn’t exactly cut and dried. For example, a lot of high quality feeds contain a component of pollard and bran, and used properly these ingredients do add value to a ration. However, if these lower quality ingredients appear to make up the majority of a feed AND the feed has only two or three main ingredients, the likelihood is that the feed is not going to give you as good a result as you could get from using a feed with better quality and more variety of ingredients.

In short, look for higher quality ‘whole’ ingredients and lots of them in an ingredient list for a higher quality feed.

Protein Quality

Protein quality is one of, if not the major characteristic of a feed that determines its quality. If a feed contains poor quality protein your horse’s coat, hooves and muscle development will all suffer. The quality of protein is determined by the amount of essential amino acids (amino acids the horse can’t make for itself) in that protein source. Proteins that have a high concentration of the most limiting essential amino acids are considered good quality while proteins with low levels of essential amino acids are considered poor quality.

The problem is, protein is usually displayed on feed labels as crude protein, which is simply calculated by multiplying the amount of nitrogen in a feed by 6.25. Nitrogen is in all protein and there is also ‘non-protein nitrogen’ sources so the crude protein really tells you nothing about the quality of protein in a feed.

To determine the protein quality you should look at the feed’s ingredients to see where the protein is coming from. Feeds containing soybean, lupins, canola meal, faba or field beans will contain higher quality protein than feeds containing protein only from cereal sources (for example the wheat protein found in wheat midds/pollard and bran) or with protein from non-specified vegetable protein meals or cottonseed meal.

Lysine is what is called the first limiting amino acid in an equine diet because it is usually the one that is first to be too low in a horse diet and therefore becomes limiting (for growth, muscle development or whatever it is your horse needs protein for at the time). So looking at the level of lysine in a feed (and also in FeedXL) will give you an indication of the quality of protein in the feed. However, there are two problems with lysine.

For learn more about protein quality, click here to read our article ‘Understanding Protein Quality in Horse Feed’.

Batching method

There are two main ways companies will ‘batch’ their feeds. The first is using least cost principles where the company will list a selection of ingredients on the label (using wording something like ‘ingredients selected from’ or broad wording like ‘cereal grains including barley, wheat and corn’) and then when they make the feed they will use whatever combination of these ingredients is the least expensive to meet the feed’s minimum requirements. Least cost batching is common practice in the pig and poultry industries and it is used to make horse feeds. While feeds made in this way will deliver the minimum nutrient specifications for each feed (so you will always get the specified level of energy, protein, vitamins and minerals) the ingredients used and thus the ingredient and protein quality can change from batch to batch.

The second method of batching used is to use the same ingredients and the same recipe each time the feed is made. This batching method give a more consistent and often higher quality product than those made using least cost batching. If you are not sure which batching method your feed supplier uses and it is something you would like to know, you should contact and ask them.

The feed mill

Another important factor determining quality is the standard of the facility used to make the feed. You should check with your feed supplier to see what sort of quality assurance programs they operate under (for example the Feed Safe program) and whether or not the mill is an equine dedicated mill (eliminating the risk of potentially fatal contamination of your feed with ingredients like ionophores (Rumensin)).

When quality really matters

Not all horses need to be fed high quality feeds. For example a good doer that is only in light work will more than likely do very nicely on good quality forage and if need be a small amount of a lower quality feed. However, horses that are under a lot of physical pressure, for example broodmares that are breeding every year, young, growing horses, horses that need to gain a lot of body condition or build muscle mass and horses in heavy work will always do a lot better on a quality feed with good ingredients and high quality protein.

The quality of forage your horse is eating also has an impact on how good a quality feed you need to feed for the best results. Horses on low quality forage, and particularly low quality C4 or subtropical type forage will always do better when fed a high quality feed with good quality protein. Horses on high quality forage will often do well when eating a lower quality feed.

So when you are next choosing a feed for your horse take notice of what and how many ingredients are used and consider what the protein quality is likely to be. If it is important to you, look at how the feed is batched and check out the quality assurance programs used by the manufacturer. You then of course also need to make sure the feed fits into your horse’s diet in FeedXL. Using both your own knowledge of feed quality together with FeedXL’s calculations will always give you the best results.

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.



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

We would love to welcome you to our FeedXL Horse Nutrition Facebook Group. Ask questions and have them answered by PhD and Masters qualified equine nutritionists and spend time with like-minded horse owners. It’s free!

Click here to join the FeedXL Horse Nutrition Facebook Group


Garlic cloves

Garlic for Horses: Should You Feed It?

Herbs have been used in some cultures as remedies for disease and illness for more than 5000 years and their effectiveness as part of an ‘integrated system of primary health care’ is well recognised. Given the benefits we see in humans, it is becoming more and more commonplace to use herbs like garlic for horses. However, in many cases for horses, herbs are used not as part of a holistic approach to health care, but rather as a nutritional supplement.

Herbs are commonly added to diets as sources of copper, sulphur, zinc, selenium and iodine. The problem is, most herbs actually contain very little of these nutrients (with the exception of iodine in seaweed). So to supply any real amounts of nutrients, these ingredients need to be fed at high levels … The problem is, some herbal products like garlic can be toxic for horses, especially if you feed them at high rates. So, if you are considering feeding garlic to your horse, you first need to consider the potential benefit to be gained versus the risks involved.

Why is garlic even considered as a feed ingredient?

The answer to this question is likely because we as humans have used it with good effect in our own diets for thousands of years. Traditionally in human medicine, garlic is used as an anti-microbial agent. A compound called allicin, present in garlic, is known to have an anti-microbial effect which (along with some other compounds) is thought to give garlic this property. Garlic also has a well liked taste and smell and is used to give food flavour.

As humans, we all too often fall into the trap of thinking what is good for us must be good for our animals. But take chocolate, macadamia nuts, garlic and onions as an example. All of these foods are eaten extensively by humans and all (yes, even chocolate) have health benefits when eaten in moderation – yet every one of these foods is poisonous to dogs, highlighting that just because we can eat it and receive health benefits, it doesn’t mean that our companions, including our horses can.

We really don’t know the answer to this question. There is also a question over whether it kills off beneficial bacteria in the horse’s gut, which the horse relies on to digest fibre. I guess the real question is WHY do we want to feed a horse an anti-microbial agent all the time? It would make more sense to only feed one when the horse is at risk of microbial infection. We would never consider giving antibiotics all the time, so why is garlic any different. Perhaps the perception that it is ‘natural’ makes us feel more inclined to use it all the time rather than just when it may be needed. Sometimes it is fed all the time in a horse’s diet not as an anti-microbial, but as a nutrition supplement, raising the question of whether it is useful for this purpose.

Does garlic provide a horse with beneficial nutrients?

As a nutritional supplement to supply vitamins and minerals, garlic rates poorly. Feeding 100 grams of dried garlic per day (which is far more than I suspect any of you would be feeding) provides the following nutrients for a 500 kg horse in moderate work (shown as percent of Recommended Daily Intake or RDI):

Nutrient % RDI supplied by 100 g/day dried garlic
Calcium 1.1
Phosphorous 1.3
Copper 0.4
Zinc 0.6
Selenium 1.1
Manganese 0.8
Iodine 0.0
Iron 0.6

As you can see from the table above, garlic provides less than 2% of a horse’s daily requirement for these minerals and as such is virtually useless as a ‘mineral supplement’.Try this in your own horse’s diet in FeedXL, enter 100 grams of garlic in the diet and look at the graph to see what it contributes to the diet; its nutritional effect is virtually nil.

Is garlic safe for horses?

There is much debate over whether or not garlic is safe to feed horses. A study conducted by Wendy Pearson at the University of Guelph, Canada in 2005 found that when fed at high levels (250 g/day for a 500 kg horse) garlic caused an array of changes in the horse’s blood including an increase in mean corpuscular volume (MCV), decreases in red blood cell count and blood haemoglobin concentration. These changes eventually led to a condition known as Heinz Body Anaemia. While the dose rate they used was high, the researchers note that currently a safe dose rate for horses is unknown. Because research has not been carried out looking at feeding lower doses of garlic over a long period of time we don’t know ‘scientifically’ if it is safe or not.

Onion, a close relative of garlic and containing the same toxic component (n-propyl disulfide) is also known to be toxic to horses, with research conducted in 1972 showing that consumption of onion tops caused severe anaemia. Again, this study used large amounts of onion tops to produce life threatening anaemia within 11 days, meaning the question of whether onions and garlic would be safer at lower levels still remains. However, US veterinarian Dr Karen Hayes notes in her article “Feeding Garlic – The great garlic debate” that she sees a handful of cases of Heinz Bodied Anaemia every year resulting from horses consuming wild onions in amongst their pasture or in horses who have raided a compost or garden and eaten garlic or onions, suggesting perhaps that the dose doesn’t need to be high for effects to occur. In any case, the effects the researchers have observed when feeding garlic or onions at high levels have been severe. While feeding garlic at lower levels over long periods of time may not cause a life-threatening anaemia, it may be causing anaemia that is mild enough not to be overtly noticed, but prevalent enough to reduce your horse’s stamina and performance and Dr Hayes suggests it may even affect a horse’s ability to resist disease.

If you do feed garlic and wish to continue feeding it, it would be a good idea to run a blood analysis on your horse to make sure their mean corpuscular volume, haemoglobin and packed cell volume levels are in the normal range and that no Heinz Bodies are present.

So should you feed it or not?

My normal stand on feeding garlic to horses is unless there are DEFINITE and DEMONSTRATABLE benefits associated with feeding garlic to your specific horse, don’t feed it. While it is true that it hasn’t been proven that lower dose rates of garlic will harm your horse, it also hasn’t been proven that feeding garlic to your horse provides any specific benefits. We also don’t know what garlic does to horses when fed consistently at low feeding rates.

Next time you go to tip garlic into your horses feed just take a moment to consider why you are feeding it, what benefit the horse is getting and whether it is worth taking the potential risk, even if it is only a small one. There is no doubt herbs can make valuable nutraceutical additions to diets but if you are considering using them as nutritional supplements, use FeedXL to see what it is they are actually adding to the diet.

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.



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

We would love to welcome you to our FeedXL Horse Nutrition Facebook Group. Ask questions and have them answered by PhD and Masters qualified equine nutritionists and spend time with like-minded horse owners. It’s free!

Click here to join the FeedXL Horse Nutrition Facebook Group


Feeding Flaxseed

Flaxseed (also known as linseed) is a valued feed ingredient amongst horse people. How it should be used has long been the subject of considerable debate. Its safety for horses has always been under question and methods of preparation are many and varied. This article looks at what flaxseed can add to your horse’s diet, if it is safe to feed and how it can be prepared for feeding.

What does flax add to a diet?

Flaxseed’s best known attribute is its high Omega 3 essential fatty acid content. Flaxseeds are over 40% oil and more than 50% of this oil is the omega 3 fatty acid α‐linolenic acid. A horse’s natural grazing diet is high in omega 3 fatty acids. However as we add grains like corn and barley to a horse’s diet their diet can become skewed towards having high levels of omega 6 fatty acids. Flaxseed provides a ‘natural’ way to keep the levels of omega 3 in a horse’s diet balanced without using expensive omega 3 fatty acid supplements. Adding 100 grams of flaxseed to your horse’s diet will add over 20 ml of omega 3 fatty acids.

While omega 3 fatty acids are generally the primary reason flaxseeds are fed to a horse, flaxseeds are a decent source of protein with around 24% protein and 0.9% lysine and also contain around 25% fibre.

When can flaxseed be used?

Flaxseed is useful for horses on a high grain (and therefore high omega 6 fatty acid) diet or when they are eating hay that has been in storage for some time or grazing low quality pasture. Flaxseed may also be used when horses have a dry coat and skin, if they have problems with inflammation including arthritis and sweet itch/Queensland itch or when high omega 6 oils like corn oil or sunflower oil are being fed as an energy source in the diet. Flaxseed itself can be used as a source of energy in the diet and because of its high fat attribute is often found in supplements intended to promote weight gain in horses.

How should flaxseed be prepared for feeding?

Because flaxseed is such a small seed it is best to grind flaxseeds immediately prior to feeding to break the seed coat, otherwise the seeds will pass undigested all the way through the gastrointestinal tract. It is important to grind the seeds fresh just prior to feeding as the oils in flaxseed are prone to rancidity and will go off very quickly if ground and left exposed to air. A small coffee grinder is commonly used for the purpose of grinding fresh flax straight into a horse’s feed (very gourmet!).

It is possible to purchase pre‐ground and stabilised flaxseeds if grinding your own is not an option.

Does Flaxseed have to be boiled before feeding?

Tradition says that flaxseed must be boiled before feeding it to a horse because of the risk of Prussic Acid (or hydrogen cyanide) poisoning. Anyone who has boiled flaxseed knows how messy it gets and for most the effort and mess are too much to continue persisting. Well good news … flaxseed it seems can be fed safely without being boiled.

Flaxseed contains compounds called cyanogenic glycosides. When the flaxseeds are chewed up by a horse these cyanogenic glycosides come into contact with an enzyme (β‐glycosidase) which converts it to hydrogen cyanide, which can then lead to cyanide poisoning. HOWEVER, the β‐glycosidase enzyme is destroyed by the acidic environment of the horse’s gastric stomach, meaning the cyanide is never produced in quantities large enough to cause any problems. This means you can feed flaxseed without cooking it first.

A study published in the Canadian Journal of Veterinary Research in 2002 looking at the ability of flaxseed to reduce the inflammation associated with culicoides hypersensitivity (sweet itch or Queensland itch) reported that they fed 1 lb of flaxseed per 1000 lb of bodyweight to horses (or 0.5 kg per 500 kg bodyweight) over a period of 42 days with no negative side‐effects being observed. With this dose rate being much higher than the normal 1 to 2 cups fed per day it can be concluded that flaxseed is safe to feed to horses without cooking it first.

What about soaking it?

It is possible that soaking flaxseed may actually make it dangerous as soaking the seeds would, to some extent, allow the β‐glycosidase enzyme to come into contact with the cyanogenic glycosides and allow for the production of hydrogen cyanide. So it is recommended you do not soak flaxseed before feeding.

Can flaxseed meal be fed?

Flaxseed meal is the high protein (32%) meal left over after the flaxseed oil has been extracted from the seed. Flaxseed meal can be fed to horses, however because the meal has had most of the oil extracted its primary use in a horse’s diet is as a protein supplement. The risk of cyanide poisoning from flaxseed meal is a little unclear. Because the seed is crushed during the oil extraction process it is possible for the β‐ glycosidase enzyme to come into contact with the cyanogenic glycosides, so it is likely hydrogen cyanide will be present. If you wish to feed flaxseed meal, look for meal produced using heat extraction technology as opposed to meal made from seeds that were cold pressed. There are however far better sources of quality protein available including lupins, full fat soybean, soybean meal and canola meal, without the possible risk associated with flaxseed meal.

Other possible side effects

Flaxseed contains phytoestrogens. Phytoestrogens are naturally occurring plant compounds that are structurally similar to estrogen. Studies in rats (Collins et al 2003) have found that feeding high levels of flaxseed to rats increased the number of female rats with irregular estrous cycles, suggesting flax could have a negative impact on the fertility of breeding animals. If you are breeding your mares and having any type of fertility problems it would be wise to avoid flaxseed in their diets.


Flaxseed is a useful feed ingredient for horses. It can be used to increase a horse’s omega 3 essential fatty acid intake where dietary omega 3 levels are low or when higher intakes of omega 3 for a particular horse seem beneficial. Despite popular opinion that flaxseed must be cooked prior to feeding to avoid hydrogen cyanide poisoning, studies have shown that up to 1 lb/1000 lb bodyweight (or 0.5 kg/500 kg BW) can be safely fed without cooking. Flaxseed should not be soaked prior to feeding and they should be avoided in the diets of breeding mares with a history of reproduction problems. FeedXL can be used to incorporate flaxseed into your horse’s diet so that it balances well with other feed ingredients being fed.

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.



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

We would love to welcome you to our FeedXL Horse Nutrition Facebook Group. Ask questions and have them answered by PhD and Masters qualified equine nutritionists and spend time with like-minded horse owners. It’s free!

Click here to join the FeedXL Horse Nutrition Facebook Group


Seaweed for Horses: Miracle Supplement or Massive Con?

There has been much debate about the potential benefits to be gained from feeding seaweed to horses. On one side, we have seaweed being reported as a multifunctional supplement that will act as an anthelmintic, antacid, immuno-stimulator, anti-inflammatory, anti-cancer, anti-bacterial, anti-ulcer, heavy metal scavenger, fertility enhancer, nerve calmer, thyroid stimulator and skin and coat conditioner. From the other side, seaweed is called nothing more than a con, containing potentially dangerous levels of iodine and precious little of anything else. So who is right, and is there any middle ground to be sought in this argument?

What is Seaweed?

Seaweed is a marine plant that can be found in oceans all around the world. There are approximately 1700 different varieties of seaweed and they come in three different colours; green, brown and red. The green seaweeds generally grow close to the water’s surface and are smaller than the brown and red varieties. Brown seaweed grows in slightly deeper and often cold waters, while the red seaweeds grow in very deep waters. It is the brown seaweed (also called Kelp) that is commonly fed to horses in Australia.

Why Seaweed for horses?

Generally people will add seaweed to their horse’s feed to supply trace minerals that are lacking in the pasture, hay and concentrates being fed to the horse. Effectively, seaweed is used as a trace mineral supplement.

Is Seaweed a Good Trace Mineral Supplement?

Seaweed supporters will readily tell you that seaweed contains ‘every nutrient needed by the horse’ including 48 minerals, 16 amino acids and 11 vitamins, making it sound like a very attractive and natural option for trace mineral supplementation. However, the concentration of minerals in seaweed is so low that when fed at the levels generally recommended for horses (15 to 30 grams/day) it makes virtually no contribution to satisfying a horse’s trace mineral requirements, with the exception of iodine (Table 1).

Table 1: The percent of daily nutrient requirements for a 500 kg horse in light work satisfied by 20 grams of seaweed containing 600 mg/kg of iodine or by 20 grams of a well formulated commercial trace mineral supplement.

% of daily requirement
satisfied by 20 g of
% of daily requirement
satisfied by 20 g of a
commercial trace
mineral supplement
Copper 0.01 62
Zinc 0.06 44
Selenium 0.1 52
Manganese 0.05 44
Iodine 706 68
Iron 1.96 35

When it comes down to it, seaweed gives your horse very little benefit from a trace mineral perspective (with the exception of iodine, which is grossly oversupplied), particularly when considered in comparison with a well formulated commercial supplement.

How Much Iodine Does Seaweed Contain?

The iodine concentration of seaweed is generally highly variable and depends on many factors including the variety of seaweed and the age of the blades that were harvested and analysed. In a study conducted in 2004 (Teas et al.) researchers found that the concentration of iodine in 12 different seaweeds varied from 16 mg/kg to 8165 mg/kg. They also found that within the same variety of seaweed, iodine concentration ranged from 514 mg/kg of iodine in the older sun‐bleached blades to 6571 mg/kg in the juvenile, fresh blades, demonstrating the highly variable concentrations of iodine that may be present in a seaweed product.

How Much Iodine Do Horses Need?

Horses require between 0.35 and 0.4 mg of iodine/kg of dry matter consumed per day. Thus a 500 kg horse consuming 2% of its body weight in feed per day will need between 3.5 and 4 mg of iodine per day. Iodine toxicity will occur at intakes of 5 mg/kg of dry matter consumed per day, which is equal to approximately 50 mg/day for a 500 kg horse.

Can Seaweed Cause Iodine Toxicity?

YES! Iodine toxicities can definitely occur when horses are fed too much seaweed. So, how much seaweed is too much? Well, that all depends on the concentration of iodine in the seaweed. Eighty grams of seaweed that contains 600 mg/kg of iodine will need to be fed to cause acute iodine toxicity in a 500 kg horse, while just 6 grams of seaweed containing 8000 mg of iodine/kg will cause acute toxicity in the same horse.

Chronic toxicity may also be a problem in horses. The effects of feeding relatively high concentrations of iodine to a horse over a long period of time (for example you may feed 20 grams per day of a 600 mg/kg iodine seaweed for 6 months, providing your horse that has a requirement of 2 mg of iodine/day with 12 mg of iodine per day) have never been studied in horses. Studies in humans however (Pearce et al. 2002; Mizukami et al. 1993) have shown that iodine toxicity can be precipitated through long term exposure to moderately high concentrations of dietary iodine. Thus the answer to the question ‘how much is too much?’ is ‘we don’t know’, meaning seaweed must be fed with extreme caution, if it is to be fed at all.

Is There Any Time That Seaweed Is Useful in a Horse’s Diet?

Given the high iodine concentration in seaweed, it can be useful to feed as an iodine supplement when there is a demonstrated iodine deficiency. Remember that an iodine deficiency will cause virtually exactly the same symptoms as an iodine toxicity (goitre, a dry, lustreless coat, lethargy, dullness, drowsiness and timidity, inappetence and cold intolerance). Thus the only way to diagnose and differentiate an iodine deficiency from toxicity is to carefully analyse the iodine content of the feeds your horse is eating. If an iodine deficiency is diagnosed and you decide to feed seaweed, carefully calculate the amount required by your horse using the iodine concentration specified on the particular product you are using. Do not overfeed seaweed in an attempt to rapidly correct your horse’s iodine deficiency as you will end up correcting the deficiency only to cause a damaging toxicity.

4 Things You Must Do Before You Feed Seaweed to Your Horse

  1. Consider exactly why you want to feed seaweed. If you can’t pinpoint a good reason such as a demonstrated iodine deficiency, then it is probably best you don’t feed seaweed at all.
  2. Obtain the iodine content of the seaweed product you wish to use. If the product you are considering does not specify its iodine content do not feed it. Never feed your horse anything unless you know what is in it. If you have your seaweed tested for iodine concentration, send us the analysis at FeedXL and we can put your specific analysis with the tested iodine level into your personal FeedXL database.
  3. Using the products specified iodine concentration, calculate how much you need to feed per day to satisfy but not substantially exceed your horse’s iodine requirements. When using FeedXL, this is easy. Simply put enough seaweed meal into your horse’s diet to meet the calculated iodine requirement. No pen and calculator required.
    FeedXL will also make sure that if your horse is being fed other iodine-containing supplements these are taken into account.
  4. Carefully weigh and feed the calculated amount of seaweed to your horse each day. Never give your horse free access to seaweed; this will just be an iodine toxicity waiting to happen.

A Special Note about Seaweed for Mares and Foals

There is a particular risk in feeding seaweed to pregnant and lactating mares. Excess dietary iodine accumulates in the placenta and is excreted in milk. Thus foals born to mares consuming diets high in iodine will be at risk of developing iodine toxicity. Foals from these mares may be born dead, or very weak, with a poor suckle response. Those who live and continue to suckle from their dam will likely develop skeletal abnormalities as iodine toxicity causes low serum thyroxine hormone concentrations and the thyroxine hormone is crucial for cartilage maturation and bone formation.

The Final Slime…

Think carefully about feeding seaweed to your horse. If your horse doesn’t need additional iodine in its diet then I would suggest you don’t feed seaweed. If you do decide to feed it, do so with extreme caution, ensuring that you always use FeedXL to calculate the amount to feed and weigh and feed that amount accurately. Don’t guess, it’s definitely not good for your horse’s health!

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.



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

We would love to welcome you to our FeedXL Horse Nutrition Facebook Group. Ask questions and have them answered by PhD and Masters qualified equine nutritionists and spend time with like-minded horse owners. It’s free!

Click here to join the FeedXL Horse Nutrition Facebook Group


Grains for Horses: Cooked or Uncooked?

While a lot of time is spent focussed on horses that can’t eat grain in their diet, cereal grains such as oats, barley, triticale, corn, rice, rye, sorghum and wheat form a valuable component of many horse’s rations. Selecting the most digestible grain based feed however can be confusing, with uncooked grains like whole, cracked and crushed grains being available as well as cooked grains like extruded, micronised, steam rolled or steam flaked and pelleted grains.

The question is, which form of grain is best for your horse, cooked or uncooked?

Why we cook grains

Grains are fed primarily as a source of energy in a horse’s diet and that energy is derived mainly from the white starch found in the centre of the grain. For the horse to obtain the energy from the starch it must be digested by enzymes in the small intestine.

But digesting the starch to extract the energy is not easy for the horse because it is “packaged” within the grain in a way that makes it difficult for the horse to get to. The reason grains are cooked is to make access to the starch a lot easier for the horse.

How starch is “packaged”

Starch is simply many glucose molecules all bonded together and bundled up into starch granules. These starch granules are then embedded amongst protein in a structure known as the protein matrix (Figure 1).


Figure 1: A scanning electron micrograph of the middle of a barley grain showing the starch granules embedded within the protein matrix. The starch granules are the large round objects.


The starch granules, embedded in the protein, are then encased within individual endosperm cells and protected by a cell wall. Many of these cells are packed tightly within the grain’s starchy endosperm (the white bit found in the middle of a grain). And the endosperm itself is protected by the aleurone layer and finally the entire structure is covered by the seed coat (Figure 2). Now from the plant’s perspective, all of this packaging is absolutely critical for its survival and is designed to protect the plant embryo and its stored sources of energy and protein to ensure it will be able to grow and survive for the first few days following germination.


Figure 2: The location of starch granules (stained black) within the endosperm cells of barley grain surrounded by the protein matrix (stained green) and protected by the aleurone layer and seed coat.


So, the packaging is clever and essential from the plant’s perspective, however for the horse, all of this packaging is just a nuisance and prevents the horse from being able to digest and extract the energy from the grain. In fact, this packaging was actually specifically designed to allow a grain to pass through the gastrointestinal tract of an animal undamaged so it may germinate when it is excreted in the manure.

How does this packaging stop starch digestion?

The packaging can be likened to a security system at a casino which prevents the thieves (or in this case the enzymes) from stealing the cash (the starch). To digest the starch the enzymes in the horse’s small intestine must first breech the seed coat, then penetrate the aleurone layer. Following this they need to be able to make their way through the endosperm cell walls (these are the cells that contain the starch), then burrow through the sometimes impenetrable vault of the protein matrix before finally reaching the starch granule. Then, in a cruel twist of fate, if the enzyme reaches this far, it will find that the starch is bundled so tightly into a ball that the enzymes cannot digest it. So the horse is presented with a difficult hurdle—just how does it go about extracting the energy held in the starch of cereal grains?


Enter cooked grains…

It has been recognised for many years now that to effectively digest cereal grains, horses need some help. And that help comes in the form of ‘cooking’. Cooking grains using processes like extrusion, micronising and steam flaking breaks down the barriers the enzymes have to face in reaching and digesting cereal grain starch.

How cooking helps

When grains are cooked using a combination of heat, moisture, pressure and some form of physical process like rolling or grinding, the entire structure of the grain is disrupted. To start, the seed coat and aleurone layer are broken and the endosperm cell walls are opened up. In addition, the structure of the protein matrix is physically disrupted so it is no longer able to protect the starch granules. Cooking also turns the ordered and tightly packed structure of the starch granule into an open and vulnerable structure which can be easily attacked by enzymes in a process known as gelatinisation. Cooking simply gives the horse’s enzymes access to the grain starch so they can go about their work of cutting up the starch into single glucose molecules, which the horse then absorbs from the small intestine into the body, where it is used for energy.

What about cracked grains?

Simply cracking, crushing or grinding grains is the same process as chewing and aims only to change the physical structure of the grain, breaking the seed coat and reducing the grains particle size to give the enzymes better access to the starch within the centre of the grain. While the seed coat and aleurone layer barriers are removed, physical processing only causes minor damage to the endosperm cell walls and leaves a majority of the protein matrix and starch granule structure intact, meaning only small improvements to starch digestion will be made. Work conducted in horses showed that cracking corn only improved its digestibility in the small intestine of the horse by 1%. So while physical processing can get an enzyme through the front doors of the casino, gives them access to some of the cash floating around at the tables, and maybe even gets them into the strong room, it leaves the enzymes without a key, security code or set of explosives to get it into the vault. In short, they aren’t much better than whole grains.

Does soaking grains help?

Soaking grains simply makes them much easier to chew, so soaking will help the horse to break the seed coat and aleurone layer barriers. However soaking does nothing to disrupt the endosperm cell wall, protein matrix or starch granule structure, so, like cracking grains, soaking does not help to improve starch digestion.

What happens if cereal grains are fed without being cooked?

Starch from grains fed whole or cracked will remain largely undigested as it passes through the small intestine and will eventually be delivered to the hindgut. This is where the trouble begins. The bacteria in the hindgut do not face the same barriers as the enzymes in the small intestine, and they are able to reach and rapidly ferment the starch contained in uncooked grains. This rapid fermentation of starch causes excessive production of acids, which accumulate in the hindgut and lower the hindgut pH (the hindgut contents become acidic). Low pH in the horse’s hindgut causes a multitude of diseases and behavioural disturbances including laminitis, colic, endotoxaemia, systemic acidosis, reduced fibre fermentation, poorappetite, wood chewing and the eating of bedding as well as deficiencies in the B-group vitamins (including biotin) and vitamin K.

What about oats?

The general consensus is that oats can be fed unprocessed. As it is a larger grain, horses are capable of chewing the grain enough to break its seed coat, removing the need for physical processing. Studies have also found that oat starch is far easier to digest than corn or barley starch in an uncooked form. So oats can be fed whole and uncooked. However, whether oats can be fed unprocessed needs to be decided on a horse by horse basis. Observe your horse’s manure closely when you are feeding him oats. If you observe whole oat grains in his manure, whole oats is not a suitable feed for this horse. It is important to make sure the oats you are observing in the manure are whole and not just undigested hulls. Do this by taking them from the manure and squeezing them. If they are whole you will observe the white starch oozing from the centre. If you want to feed oats specifically, but your horse doesn’t digest them well, cracked, steam rolled and micronised oats can be purchased.

And the moral of the story…

Don’t feed cereal grains unless they have been cooked, with the exception of oats for some horses. If you feed whole, uncooked cereal grains, your horse will get little benefit from them and they have a good chance of causing disease and behavioural problems. Remember, the reason you feed cereal grains is to provide your horse with a source of energy. Most of this energy is held within the grain’s starch. If the horse can’t digest this starch, then you are better off not feeding the grain at all.

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.



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

We would love to welcome you to our FeedXL Horse Nutrition Facebook Group. Ask questions and have them answered by PhD and Masters qualified equine nutritionists and spend time with like-minded horse owners. It’s free!

Click here to join the FeedXL Horse Nutrition Facebook Group


Alfalfa (Lucerne) Hay: Friend or Foe?

Also known as lucerne in some parts of the world, alfalfa hay enjoys a varied reputation amongst horse people, with some using it as a highly valued component of their horse’s diet and others avoiding it with almost religious fervour. So, who is right? Is alfalfa hay a suitable forage for horses? Or are there other more suitable forages? The answer is yes, and yes. Alfalfa hay is a valuable forage for horses when fed to the right classes of horses and in the correct amounts for its full benefit to be realised. The following article looks at the nutrients contained in alfalfa hay and its many and varied uses in the horse industry.

Nutrient profile

Figure 1: A comparison of the digestible energy (DE), crude protein (CP), calcium (Ca), phosphorous (P) and magnesium content of early bloom lucerne hay, grass hay and oaten chaff.

Good quality alfalfa hay contains more protein and energy than grass or cereal hays and chaffs (Figure 1). Alfalfa also contains high concentrations of calcium and magnesium, and when fresh, the vitamins A and E. Alfalfa is typically low in phosphorous and depending on where it was grown, contains varying concentrations of other micro and macro minerals. The protein in alfalfa hay is of high quality and contains appreciable amounts of the essential amino acid lysine.

When to feed alfalfa?

To answer that question, we must consider the strengths and weaknesses of alfalfa hay. Firstly, note that there are no known anti‐nutritive factors in alfalfa hay. It is a very high quality, safe feed. However the higher energy and protein in alfalfa hay can result in too much energy and/or too much protein in the horse’s diet if you feed too much, so it is important to keep these nutrients in the diet within the recommended daily intake limits (RDI’s). Too much protein and/or energy can result in some problems for horses which are discussed below. As with all hays, some nutrients are lacking, particularly some of the trace‐minerals, so when feeding alfalfa hay it is important to ensure you are meeting the RDI’s when balancing your horse’s diet. The use of alfalfa hay in the diet of various classes of horses is discussed below:

1. Performance horses in training and competition

Alfalfa hay can be used to provide energy, good quality protein and a source of fibre to the diet of a performance horse; however, it must be used in moderation. Excess protein in the diet of working horses and particularly those that are stabled can be detrimental to their health and performance. Excess protein intake will increase urinary ammonia production, which may then result in respiratory problems for horses confined to a stable. Excess protein can also contribute to dehydration due to water loss through increased urine production and excretion and increases the amount of heat produced during the digestion and utilisation of feedstuffs. Therefore a diet containing protein in excess of the horse’s requirement can increase the horse’s water and electrolyte loss through sweating and can contribute to hyperthermia, and decreased performance or endurance capacity.

It is important to understand that these effects are not as a direct result of feeding alfalfa, but rather from feeding too much alfalfa. Avoid them by keeping protein within the RDI limits. Use a grass or cereal hay to supply some of the horse’s roughage/fibre requirement.

2. Spelling or idle horses

Alfalfa hay can play a role in the spelling or idle horse’s diet, and will provide these horses with good quality protein and calcium. If you keep energy and protein within your horse’s RDI, you can safely feed alfalfa without having excess weight gain due primarily to too much energy.

3. Ponies

Ponies may be safely fed alfalfa hay, but again it must be fed in moderation. Alfalfa hay, because of its highly digestible nature is capable of encouraging significant weight gain in ponies, particularly those that are easy keepers. Feeding too much alfalfa hay may therefore predisposeponies to laminitis, as the risk of laminitis increases when ponies become overweight (again, this is not as a result of feeding alfalfa, but as a result of feeding too much energy and protein which in turn leads to excess weight gain). Keep energy and protein within the recommended daily limits when using alfalfa in the diets of ponies.

Alfalfa hay is very useful in the diet of aged ponies. As horses and ponies age, they lose some ability to digest fibre and protein. Feeding them an easily digested fibre and high quality protein source in the form of alfalfa hay will help them maintain bodyweight, particularly in winter.

4. HYPP and laminitic horses

Alfalfa hay may not be suitable for horses suffering with hyperkalaemic periodic paralysis (HYPP) as its concentration of potassium is often quite high (14 – 25+ g/kg). Make sure you keep potassium in particular at the 100% RDI in these horses, regardless of the feeds you use.

In the reverse, and contrary to popular opinion, alfalfa hay is a very suitable feedstuff for horses that have suffered a bout of laminitis. The high quality protein in alfalfa hay will help the horse to repair its damaged laminae while the energy derived from the alfalfa will prevent these horses from entering a negative energy balance which slows or prevents the hoof’s healing process taking place. In comparison to some grass hays, alfalfa also contains a lower level of starches and sugars. Again, make sure you feed alfalfa hay in moderation to prevent excess weight gain; don’t exceed the energy and protein RDI’s in FeedXL.

5. Growing Horses

Alfalfa is a valuable forage in the diet of growing horses. Alfalfa provides growing horses with a digestible source of energy as well as a source of high quality protein and the essential amino acid lysine. Alfalfa’s calcium rich characteristic is also beneficial for growing horses that typically have high calcium requirements.

However, when feeding alfalfa to growing horses, the amount fed should not exceed the growing horse’s energy requirements. Growing horses fed energy in excess of their RDI’s have a much higher chance of suffering from developmental orthopaedic diseases including osteochondritis dissecans (OCD).

Feeding protein in excess of the growing horse’s protein requirements does not appear to be detrimental as the protein can be utilised as a source of energy. However, protein is an expensive source of energy and to quote Susan Garlinghouse “it is sort of like using bundles of dollar bills to start a barbeque. It’ll get the job done, but there are much cheaper, easier and more efficient ways of doing it”. Therefore, instead of using alfalfa hay to meet 100% of a growing horse’s energy requirements (which will far exceed their protein requirements) it would (depending on pasture conditions) be more economical to use some form of cereal grain or high energy fibre like sugarbeet pulp or soybean hulls to provide additional energy in the diet when needed.

Another point to be aware of when feeding alfalfa hay to growing horses is their intake of phosphorous. While feeding alfalfa hay to meet a growing horse’s protein requirements will also in most cases meet their calcium requirements, their phosphorous requirements will not be met. Feeding cereal grains will help to increase a growing horse’s intake of phosphorous, however, in many cases, phosphorous supplementation may be required (remembering that the calcium to phosphorous ratio in the diet of a growing horse should be maintained within the range of 1: 1 to 3: 1). Dicalcium phosphate is a suitable source of phosphorous for growing horses.

Also keep in mind that alfalfa hay is not a complete feed and will more often than not contain insufficient concentrations of trace minerals, in particular copper and zinc, to support sound musculoskeletal development. Thus diets utilising alfalfa hay as a protein and energy source must be balanced using an appropriate trace mineral supplement for the best results.

Once again, getting the diet balanced for the nutrient RDI’s in FeedXL is vital to making the best use of alfalfa.

6. Pregnant and Lactating Mares

Alfalfa hay is an exceptional source of energy and good quality protein for pregnant and lactating mares. Alfalfa hay will also help to support these mares’ elevated requirements for calcium and the essential amino acid lysine.

When feeding the pregnant mare alfalfa hay, take care not to exceed her energy requirements since this can cause her to become overweight. Pregnant mares should remain within a body condition score of 5 to 7 (using the Henneke scale of condition scoring) to prevent reduced milk production during the lactation period.

The lactatating mare’s energy requirements however are higher, and alfalfa hay alone will not be capable of meeting these and may, depending on pasture conditions, need to be fed in conjunction with cereal grains or high energy fibres to maintain body condition throughout lactation. Likewise, the lactating mare’s phosphorous and trace mineral requirements will not be met by a diet of alfalfa hay, thus these must also be supplemented accordingly.

As with growing horses, excess protein in the diet of pregnant and lactating mares does not appear to be harmful, however it is an unnecessary waste of this relatively expensive feed component and should be avoided if possible.

In Conclusion

Alfalfa is a valuable feedstuff for horses and is capable of providing them with energy, high quality protein, lysine, calcium and varying levels of other vitamins and minerals. However, alfalfa hay must be used correctly in the diets of all horses to realise its full benefits. Problems with the feeding of excess energy and protein are possible when feeding alfalfa hay so keep a close watch on those energy and protein RDI’s. Use grass/meadow hays in conjunction with alfalfa hay to fulfil a horse’s roughage requirement and well chosen supplements to fulfil mineral requirements. This will help you balance the diet and avoid some of the problems that can be associated with over‐feeding alfalfa hay.

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.



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

We would love to welcome you to our FeedXL Horse Nutrition Facebook Group. Ask questions and have them answered by PhD and Masters qualified equine nutritionists and spend time with like-minded horse owners. It’s free!

Click here to join the FeedXL Horse Nutrition Facebook Group


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