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):

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

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):

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

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.

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