Tag Archive for: feed ingredients

Oil for Horses: Good or Bad?

Hard working horses have enormous requirements for energy that are traditionally filled using high grain rations fed together with chaff and hay. However, feeding large amounts of grain does come with its own set of issues which can include colic, hindgut acidosis, nervous or fiery behaviour, tying up and loss of appetite. Oil has gained popularity in recent years as a substitute source of energy for working horses, but is it effective, how much can be fed, are all oils equal in the benefits they can provide and do they cause any health issues of their own?

A little bit goes a long way

The biggest benefit oils provide working horses is their very high energy content relative to grains. Oils contain nearly 3 times more energy than oats, with 400 mls of vegetable oil providing as much energy as 1 kg of oats. The real benefit in this is you can reduce the size and sheer bulk of feed a horse has to consume without reducing calorie intake, allowing you to get enough ‘feed’ into horses with poor appetites. The end result being these horses can hold their weight and continue to train and compete for longer than they otherwise would on a more traditional diet.

Reducing heat load

Oils generate less heat during the digestive and metabolic processes than an equivalent amount of grain or forage. Feeding oil also means that you can feed less grain and still meet energy requirements. Combined, this means that high oil diets place less of a heat load on working horses, reducing electrolyte losses and the amount they need to sweat to stay cool, a big bonus for hard working horses, especially those training and racing in hot environments or working over very long distances.

Saving glycogen

Fatty acids from oils are the preferred fuel for muscles during slow and medium pace work while glycogen is the only source of energy a muscle can use during sprints and strenuous exercise. Once a horse runs out of glycogen its muscles fatigue and the horse will slow down and lose the ability to perform at the level it is capable of. Feeding oil in diets provides a source of fatty acids for muscles to burn during the warm up and slower phases of a competition, meaning muscles are able to conserve valuable glycogen and avoid fatigue.

Problem solving

‘Problem horses’ and particularly those that tie up or get excited and nervous on high grain diets will often benefit from rations that provide a portion of the dietary energy from oils. It is thought that the positive effects seen in these horses on high oil diets is due more to the reduction in grain intake as opposed to the addition of oil, but using oil in the diet allows you to reduce grain intake without compromising energy intake and performance.

Oils aint oils

All oils contain virtually the same amount of digestible energy, but there are other differences you may want to consider when looking to purchase an oil, including:

Essential Fatty Acid Content: Horses need omega 3 and omega 6 fatty acids in their diet. Grains are naturally high in Omega 6, so for horses on a high grain diet, it is preferable to choose an oil with some omega 3 content. The table below shows the amount of omega 3 and omega 6 in some commonly used oils. Linseed and canola oil contains the highest omega 3 fatty acid content of the natural vegetable oils.

Ingredient Name Omega 3 (%) Omega 6 (%)
Linseed (Flax) Oil 57 13.9
Cod Liver Oil 25 2
Canola Oil 10 20
Soybean Oil 7 52
 Corn Oil  1  55
 Olive Oil  1  11
 Rice Bran Oil  1  39
 Sunflower Oil  0.3  60
 Coconut Oil  0.1  2

Some linseed oils and fish oil including cod liver oil are notoriously unpalatable for horses, so while these oils are useful for providing omega 3 fatty acids, they can’t be fed in large amounts as most horses simply won’t eat them.

Processing Method: Oil is extracted from oilseeds in two main ways; cold pressing where oil is squeezed out of seeds, often in a water cooled environment to keep the oil at less than 60C; and solvent extraction where a solvent like hexane is added to extract oil from seeds. The oil is then heated to remove the hexane. Cold pressed oils tend to be higher in quality as more of their essential fatty acids and natural antioxidants are left intact in comparison to solvent extracted oils.

It takes time

Horses need time to adapt to digesting and metabolising oils. Oils should always be introduced into a diet slowly, starting with ¼ cup of oil per day and increasing this by ¼ cup every 5 days until you reach the full amount you want to feed. Introducing oil into a diet too quickly can result in soft manure and reduced fibre fermentation in the hindgut.

It will take a minimum of 3 weeks before a horse starts to really benefit from the oil in its diet and it could take up to 3 months before the full benefits of oil are realised.

How much can you feed?

Horses can be fed up to 20% of their total energy intake as oil, which in real terms means just over 3 cups of oil per day for a 500 kg horse in full work. While this level of oil is useful for horses that tie up, very few horses are fed this much oil per day. Feeding between 1 and 2 cups of oil per day is enough to give horses the benefits discussed above without making diets messy, unpalatable or unnecessarily expensive.

Good Stuff

Oils are ‘good stuff’ for working horses. They reduce reliance on grains, make the amount of feed a horse needs to eat smaller, keep horses cooler, allow horses to conserve muscle fuel for sprinting, give horses that tie up a safer and more effective source of energy and provide essential fatty acids in the diet.

For the best results, introduce oils slowly into the diet and select oils based on the following: their omega fatty acid content with oils containing some omega 3 fatty acids preferred; palatability, be aware that some oils including linseed and fish oils can be unpalatable; and method of processing, with cold pressed oils preferred over solvent extracted oils.

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


Horse standing in field

Does Your Horse Need Electrolytes?

As a horse exercises its muscles generate heat. To prevent its body from dangerously overheating, the horse sweats to allow evaporative cooling to dissipate the heat being produced. As a horse sweats, water and electrolytes, including sodium, chloride, potassium, magnesium and calcium are lost from the body.

For effective sweating to occur, the horse must be well hydrated and have an ample supply of electrolytes in its body. The electrolytes and water lost through sweating must be replaced following exercise to prevent electrolyte depletion and dehydration.

In this blog post we will look at what electrolytes are and why they are important, how much ‘electrolyte’ a horse needs, where horses get electrolytes from in the diet and when to use an electrolyte supplement.

What are electrolytes?

Very simply, electrolytes are minerals, which, when present in a watery solution like body fluids, become positively or negatively charged particles that have the ability to conduct electricity. Electrolytes maintain fluid balance and circulatory function, facilitate muscle contractions, trigger nerve functions and maintain the body’s acid-base balance. The most important electrolyte minerals are sodium, chloride, potassium, magnesium and calcium.

What happens if a horse becomes electrolyte deficient?

Electrolyte deficiencies are associated with fatigue, muscle weakness, lethargy and reduced feed and water intakes, resulting in weight loss and dehydration. In addition, electrolyte deficient horses may experience reduced sweating, which can result in hyperthermia (over-heating) and compromised performance. Studies in England have also linked electrolyte deficiencies to the incidence of recurring bouts of tying-up (Harris et al. 1992).

Please Note: severe electrolyte deficiency can result in complete exhaustion, colic, synchronous diaphragmatic flutter (commonly known as the ‘thumps’), collapse and death if not treated. Severe electrolyte deficiencies are a veterinary emergency requiring IV fluids, electrolytes and specialist care so please call your vet immediately if you suspect your horse is acutely dehydrated and electrolyte deficient.

How much ‘electrolyte’ does a horse need?

All horses have a small daily requirement for electrolytes to replace the obligatory losses from the body in the urine and faeces. This requirement is termed a horse’s ‘maintenance requirement’ and is reflected in FeedXL’s recommended daily intakes for horses not in work.

Sweating increases a horse’s requirement for electrolytes above their maintenance requirement, as large quantities of sodium, potassium and chloride and smaller quantities of magnesium and calcium are excreted in sweat (amounts are given in the table below):

Electrolyte Sodium Potassium Chloride Magnesium Calcium
Quantity in sweat* (grams/L) 3.1 1.6 5.5 0.05 0.12

The amount a horse sweats, and therefore its electrolyte requirement, will be determined by the amount of work it is doing, the intensity of work it is performing and the climatic conditions in which the horse lives and works. Individual horses also vary considerably in their tendency to sweat. As an indication, in a moderate climate, a racing thoroughbred will lose between 5 and 10 litres of sweat during a daily workout and an endurance horse will excrete between 5 and 10 litres of sweat per hour when travelling between 12 and 18 km/hour. Sweat losses of up to 15 litres/hour can occur during high intensity exercise where horses are travelling at between 30 – 35 km/hour.

FeedXL calculates your horse’s electrolyte requirements for you based on a sweat loss of 1.6 L per day for horses in light work, 4.4 L per day for horses in moderate work, 6.7 L per day for horses in moderately heavy work and 8.9 L per day for horses in heavy work.

How does climate affect requirements?

Hot and particularly hot and humid climates increase a horse’s need for electrolytes as horses will sweat more under these conditions. As a general guide, if the temperature is 30C (86F) supply 140% of your horse’s recommended daily intake (RDI) calculated by FeedXL for sodium, potassium and chloride . If the temperature is 35C (95F), supply 170% of your horse’s calculated requirement for these minerals and if the temperature is 40C (104F) or over you should supply 200% of their requirements. Also be sure to have a salt lick available at all times.

Where do electrolytes come from?

Pastures and forages are almost always a rich source of potassium and are commonly a good source of magnesium. However they tend to contain variable and often unknown concentrations of chloride and typically low concentrations of sodium. Common table salt contains 39% sodium and 61% chloride and is frequently used as a readily available, palatable and cheap source of these electrolytes in a horse’s diet. Potassium chloride (50% potassium, 47% chloride) can be used to supply additional potassium and chloride where required and magnesium oxide is a readily available and cost effective source of magnesium where additional magnesium is needed. Grains contain only very small amounts of all the electrolyte minerals and it is high grain diets that are most commonly ‘electrolyte deficient’.

When should you feed an electrolyte supplement?

In many situations horses can get enough electrolyte minerals from a forage based diet that has plain table salt added for additional sodium and chloride. Some horses on high grain/low forage diets may benefit from an electrolyte supplement that contains potassium or need potassium chloride added to their feeds. On a day to day basis though, most horses won’t need a commercial electrolyte supplement.

Commercial electrolyte supplements are however very handy in situations where your horse is away from home, not grazing or eating as much hay as he normally would and/or working a lot harder or longer and sweating more than usual. Well formulated supplements (ones that contain the same proportion of electrolytes as those found in equine sweat) can be used in these situations to quickly replace electrolytes lost in sweat. Where prolonged exercise occurs (for example endurance riding or long days of stockwork or trail riding) it may be necessary to provide some electrolytes during the period of exercise.

Well formulated electrolyte supplements will provide enough electrolyte minerals in a 60 gram dose to replace the salts lost in 5 litres of sweat. There is debate over how much electrolyte replacer you should give to working horses with no firm recommendations available given it does depend so much on the climate, intensity of work and the horse as an individual. If a horse is sweating consistently over a long period of time AND will have access to water frequently you can give 60 grams of electrolyte every hour to two hours. If water is not available on a frequent basis give 60 grams of electrolyte when you know the horse will have access to water and can have a good drink. Don’t give more than 60 grams per dose as you may overload the horses ability to absorb the salts you give.

Well formulated electrolyte supplements will contain 20 – 25% sodium, 43 – 48% chloride, 10 – 12% potassium and smaller amounts of magnesium and calcium (normally 1 to 2%). These higher quality products will also have less than 20% glucose or other base or filler.

Some practical tips for using electrolyte supplements

  1. Always make sure your horse has access to water after being given electrolytes as they will get thirsty and need to be able to drink. Failure to provide water will result in dehydration because the salts will pull water out of the body and into the gut.
  2. If it is possible, wait for your horse to have a drink of water before giving it electrolytes.
  3. Never give electrolytes to an already dehydrated horse that isn’t drinking as you will worsen the dehydration. Call your vet in these situations.
  4. Don’t add electrolyte supplements to a fussy horse’s feed as chances are it won’t eat them. Instead mix the electrolyte with apple sauce and give it over the tongue (beware they will spit it all over you!).
  5. During endurance rides where feed intake is also important, allow your horse to eat before giving him electrolytes as a paste as it will often stop a horse from eating for a little while which may affect your gut noise scores.
  6. Always have a salt lick available to allow your horse access to extra sodium and chloride at any time.
  7. If you want to use an electrolyte to help make your horse drink when away from home try it out at home to see if it works – if you dose your horse with electrolytes and he doesn’t drink he will actually end up more dehydrated than when you started.
  8. To increase water intake, offer slightly salty water to your horse as its first drink after exercise. Research has shown (Schott et al 2003) that horses who drink slightly salty water (0.9% salt, 90 grams of salt per 10 litres of water) initially will drink more water and rehydrate themselves faster after exercise than horse who drink plain water as their first drink. You will likely need to train your horses to drink the salty water, a touch of molasses might help.

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


The Importance of Fibre for Horses

Several different forms of carbohydrates form what we call ‘fibre’. These carbohydrates include cellulose, hemicelluloses and lignin. Fibre cannot be digested in a horse’s small intestine. Instead, the horse relies on the billions of bacteria that live in the hindgut to digest the fibre by fermentation. Fibre, which is also called ‘structural carbohydrate’, is essentially provided by the pasture, hay, chaff, haylage and high fibre feeds like sugarbeet and legume hulls in your horse’s diet. Fibre is the single most important component of a horse’s diet (after water) as without it, their digestive tract can’t function as it should. So why is it so important and what will happen if your horse doesn’t get enough?

Why do horses need fibre?

Fibre plays 3 very important roles in the diet of horses. These are:

  1. Fibre provides a source of energy/calories for horses. While the horse itself cannot ‘digest’ the carbohydrates that form fibre (because like humans they don’t have the necessary digestive enzymes to break it down in the small intestine), the horse houses billions of bacteria in its hindgut that do the job of digesting fibre for it. So, the horse provides the bacteria somewhere safe and warm to live and in return the bacteria pass on to the horse most of the energy contained in the fibre.
    As well as providing the horse with energy, important vitamins like vitamin B1, biotin and vitamin K are produced during the bacterial fermentation of fibre in the hindgut.
  2. Fibre provides the horse with ‘gut fill’. The horse’s gastrointestinal tract is an ENORMOUS organ and it needs to be kept full. The fibre in a horse’s diet is what provides the bulk to keep the gut full and healthy.
  3. Fibre soaks up and holds water in the gut to act as a water reserve when horses need it.

What happens if a horse doesn’t get enough fibre?

Diets that don’t provide a horse with enough fibre can cause major problems including:

  1. Colic – if a horse’s gastrointestinal tract is not kept full it is prone to twisting about and moving in ways that it can’t normally when it is full of fibre. Unfortunately for the horse this can lead to serious colic that can only be resolved (if the horse is lucky) by surgery.
  2. Diarrhoea – low fibre diets very often result in loose sloppy manure, which in-turn affects the whole dynamic of how the gut works. Horses with diarrhoea digest what fibre they do get less efficiently and they are prone to problems with dehydration and electrolyte deficiency.
  3. Dehydration – horses on a low fibre diet don’t have a readily available water reserve in their gut, meaning if they sweat heavily or spend an extended period of time away from water they are more prone to dehydration than a horse on a high fibre diet. Problems with diarrhoea as discussed above make this issue worse.
  4. Energy deficiency – horses that aren’t being fed enough fibre are also most likely not being fed enough energy (calories) so they may be losing weight or having difficulty gaining weight. The energy value of fibre is often underestimated, with forages like oaten hay or chaff often being viewed simply as a ‘filler’ when in fact they are a valuable source of energy for horses.
  5. Vitamin Deficiency – the bacteria that ferment fibre in the hindgut also produce several vitamins including vitamin B1, biotin and vitamin K for horses. If horses aren’t fed enough fibre the bacteria are unable to produce the amount of vitamins they normally would and a deficiency may result leading to problems like loss of appetite and poor quality hoof growth.
  6. Boredom – horses on low fibre diets will often have a lot of spare time to fill in during the day that ordinarily they would be spending eating. This boredom will often lead to problems like cribbing, weaving and chewing on strange objects or eating dirt.
  7. Gastric ulcers – the horse’s stomach is constantly releasing gastric acid and the horse relies on eating fibrous feeds to help prevent gastric ulcers. Chewing high fibre feeds like pasture or hay generates a lot of saliva which acts to buffer the gastric acid. Fibre also provides a raft in the stomach that helps to stop acid from the lower portions of the stomach from splashing up and damaging the unprotected upper portions of the stomach. Low fibre diets can’t provide this protection for horses.
  8. Constant hunger – because fibre is the part of the diet that provides the ‘gut fill’ a diet low in fibre will leave a horse always feeling hungry, which then causes its own set of problems including behavioural issues and even sand colic (see below).
  9. Sand colic – when horses are fed low fibre diets it increases the chance that sand and dirt will accumulate in their hindgut and cause colic or diarrhoea. Feeding large amounts of forage is one of the most effective ways to remove sand and dirt from the hindgut. The increased risk of sand colic in horses on low fibre diets is also partly also related to the fact that horses on low fibre diets are often hungry and if housed on dirt or sand will be going around vacuuming everything off the ground, and picking up large amounts of dirt and sand in the process.

What types of feed are high in fibre?

As you can see fibre is absolutely essential in a horse’s diet. Feeds that contain a lot of fibre include:

  • All types of hay and chaff
  • Most pastures (very lush green pastures are quite low in fibre)
  • Haylage
  • Sugarbeet pulp
  • Legume hulls including soybean and lupin hulls
  • Copra meal
  • Seed hulls including oat and sunflower seed hulls

How much fibre does a horse need per day?

Recent recommendations are that horses should be fed a minimum of 1.5% of their bodyweight per day in forage (pasture, hay, chaff, haylage; Harris et al. 2017). This is equivalent to 1.5 kg/100 kg bodyweight or 1.5 lb per 100 lb bodyweight (which equals 7.5 kg/day for a 500 kg horse; 16.5 lb/day for an 1100 lb horse). Essentially though the more fibre you can feed in your horse’s diet the better. Use FeedXL to see if you can meet your horse’s energy requirements with high fibre feeds alone (focussing mainly on pasture and hay) and then just top up whatever vitamins and minerals are missing using a vitamin and mineral supplement.

It isn’t always possible to feed like this however and horses that are working hard need higher energy feeds like oils and cereal grains in their diet. Even for these horses it is still critically important that they are fed 1% of their bodyweight in high fibre forage.

Any of the feeds listed above can be used to provide ‘fibre’ in a horse’s diet. A second good rule of thumb to follow is to provide at least half of the fibre in your horse’s diet as long stem fibre in the form of hay or pasture. The long stem fibre takes the horse longer to eat (so keeps them happier) and also makes them chew more, which encourages more saliva production, which is important for gut health too. These long stem fibres also contain what is known as effective fibre, which is fibre that remains undigested as it passes through the gut. Effective fibre is important for allowing the horse to produce manure and shift unwanted material like sand out of the hindgut.

What other nutrients do forages provide?

High fibre forages (like pasture, hay, chaff and haylage) are a valuable source of protein. In fact for many horses these forage are more than capable of meeting 100% of their energy and protein requirements – FeedXL will show you if this is the case for your horse. Forages are particularly rich in the electrolyte mineral potassium (and sometimes contain too much of this minerals, read our FeedXL Newsletter ‘Is Pasture Affecting your Horse’s Behaviour’) and also contain good amounts of calcium, phosphorus and magnesium and varying amounts of other trace minerals (we recommend having your forages tested so you know exactly what your forage is providing your horse, then you can use FeedXL to just add what is needed). Fresh green forages are also particularly rich in vitamin A, E and K and the B-group vitamins and they are an excellent source of omega 3 fatty acids.

The final straw

Horses evolved eating a high fibre diet and fibre is still the single most important component in your horse’s diet aside from water. If your horse isn’t getting enough fibre it can be facing serious consequences including colic, dehydration, diarrhoea, ulcers, vitamin deficiency, weight loss and behavioural problems. So be sure to feed enough, it will keep your horses much healthier and far more content.

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


Protein: Can You Feed Too Much?

Protein is a very important component of all horse diets and as discussed in our post ‘Understanding Protein Quality’, the quality of protein used in diets will largely determine how well that diet can support functions that rely on protein including growth, reproduction, athletic performance and muscle building.

But can we get carried away with protein in a horse’s diet? Can too much protein be fed? And are the very high protein pastures that are so common nowadays a problem for horses? The answer to those questions is ‘yes and no’, it all depends on the circumstances your horse find itself in. Let’s look in more detail at when high protein diets may be a problem.

Protein is expensive!

When protein is fed in excess of protein requirements the horse will simply chop the protein up, remove the nitrogen and use what is left as a source of energy, so it isn’t completely wasted. BUT feeding protein as a source of energy is sort of like using notes of money instead of old newspaper to get a fire started. It will do the job, but it is an expensive way to do it. So when formulating a diet, use FeedXL to keep protein intake as close to requirements as is practically possible.

Wet and smelly bedding

Horses on high protein diets will, as discussed above just chop the protein up and burn it essentially like a carbohydrate. But they then need to get rid of the nitrogen they didn’t need from the protein. To do this, nitrogen is turned into urea and excreted in the urine. Getting rid of waste nitrogen requires a lot of water so horses on high protein diets tend to drink AND urinate a lot. Now, this isn’t a problem if your horse has ready access to water and lives outside. But for horses in stables, feeding too much protein is going to mean a whole lot of extra wet bedding for you to muck out every day, which is time consuming and can be expensive depending on what you pay for bedding.

Perhaps a bigger issue for stabled horses on high protein diets is the strong smell of ammonia that develops as the excreted urea is converted to ammonia in the bedding. Ammonia can irritate airways and cause respiratory issues, especially in poorly ventilated stable areas, so meeting but not unnecessarily exceeding protein intakes is particularly important for horses confined to stables for long periods of time.

Heat production

The digestion and metabolism of protein generates more heat than the digestion and metabolism of fat and carbohydrate. So a horse on a high protein diet that is burning a lot of protein as a source of energy will need to get rid of more body heat and in doing this will sweat more. This increased rate of sweating, together with the extra urine production needed to remove the waste urea from the horse’s body combine to increase a horse’s water requirement.

If the horse in question is only in light work, has free access to water and doesn’t live in a hot climate, the high protein diet really won’t pose an issue. However, if a horse is in moderate to heavy work, and particularly if that work is endurance type work or the horse lives in a hot climate the excess heat production from the high protein diet could lead to problems with dehydration and heat stress. Connysson et al (2006) observed that protein intakes of 160% of requirements did disrupt fluid balance (by increasing water loss through sweating and urination) so keeping working horse protein intakes below this level may assist with maintaining good levels of hydration. These researchers observe no negative impact of this level of protein on performance in the horses studied.


Protein is sometimes blamed for making horses ‘hot’ and some horse owners will actively select low protein feeds in an effort to keep their horses calm. This however is mostly a wives tale. Diets that are higher in energy than a horse’s true energy needs can and often will make a horse hyperactive. If you are feeding a very high protein diet, chances are this diet is also going to be a high energy diet … AND all the horse is going to do with the extra protein it is being fed is cut it up and burn it for energy. So it isn’t the protein, as such, causing problems with behaviour, but instead the amount of energy in the diet.

What about the liver and kidneys?

High protein diets have also long been blamed for damaging liver and kidney function. There is no evidence (that I can find) to suggest that healthy horses with a fully functioning liver and kidneys suffer any kind of harm to these organs on a high protein diet. However if a horse has a pre-existing problem with either its liver or kidneys a low protein diet that meets but does not exceed protein requirements is recommended.

Managing protein intakes on high protein pastures

Most of the time when protein intake is indicated as being excessive in FeedXL it will be due to a very high protein pasture playing a prominent role in the diet. This may not be a problem if your horse is healthy, living in a temperate or cool environment, living outdoors and in light work, breeding, growing or not doing anything at all. However, if your horse is stabled for periods of time, living in a hot climate or is in moderate to heavy work it would be advisable to try and reduce protein intakes by reducing pasture intake. This is often best done by keeping the horse off pasture for a period of time during the day or night and providing a lower protein grass hay. The use of lucerne/alfalfa hay should also be minimised or stopped altogether when horses are grazing high protein pastures.

Use high quality protein

When feeding protein a major consideration is whether that protein is meeting your horse’s requirement for essential amino acids. Using the best quality protein you have available will allow you to meet lysine (and other essential amino acid) requirements without having to feed excessive amounts of crude protein. Using low quality protein will mean you have to feed more crude protein to meet essential amino acid requirements and the higher level of crude protein may interfere with your horse’s hydration, heat load and air quality as discussed above.

Take Home Message

If your horse:

  • lives in a hot climate
  • is stabled all or part of the time
  • is in moderate to heavy work; and/or
  • has a pre-existing liver or kidney disease

You should keep protein intakes within the acceptable limits for protein set by FeedXL (and in the case of liver or kidney disease keep intakes as close to 100% of requirements as possible) to avoid the issues discussed above.

However, if your horse is:

  • healthy
  • living in a temperate or cool environment
  • living outdoors; and
  • in light work, breeding, growing or not doing anything at all

Excess protein in the diet will simply be chopped up and used for energy. However you should still avoid feeding more protein than you need to because it is expensive and doesn’t provide any benefit to your horse.

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


Magnesium for Horses: Which Form is Best?

With so much focus on magnesium in equine diets, you may be wondering what’s the best form of magnesium for horses.

There are many ‘forms’ of magnesium available and suitable to be fed as magnesium supplements. Unfortunately, at the moment there aren’t any extensive studies that look at the comparative bioavailability of these various forms of magnesium in horses.

To help us understand which forms of magnesium are best for horses, let’s first look at where and how magnesium is absorbed.

How is magnesium absorbed?

In the horse, magnesium is absorbed from the small intestine (Hintz et al 1972), with the second half of the small intestine being slightly more effective at absorbing magnesium than the first half. It is thought that very little magnesium is absorbed from the hindgut in the horse. Small intestinal absorption of magnesium is similar to that seen in humans, rats and rabbits.

Magnesium can be absorbed a few different ways. It is thought the major process via which magnesium is absorbed is simply via passive diffusion. This is a process where magnesium simply moves from an area of high concentration to an area of lower concentration, so in the case of intestinal absorption, when the concentration of magnesium in the gut is higher than in the intestinal cells the magnesium will move across membranes to enter the body. The concentration of magnesium drives absorption in this situation so the more magnesium present in the gut, the higher the concentration and therefore the more that will be absorbed.

Solvent drag, where magnesium dissolved in water in the gut is transported into the body as water is absorbed is a second route of magnesium absorption while active transport where magnesium is transported via some sort of magnesium pump that requires energy to operate and physically drag magnesium from the gut into the body is the third mechanism demonstrated in magnesium absorption. Which of these routes of absorption play the most important role in magnesium transport in horses is unknown.

What form of magnesium is easiest for horses to absorb?

It is difficult to compare the bioavailability of various forms of magnesium between studies because different experimental methods and forms or qualities of magnesium supplements are used. A relatively recent study (2005) published in the journal ‘Magnesium Research’ reported the magnesium bioavailability from 4 inorganic and 6 organic mineral salts of magnesium in rats. This was the most comprehensive study I was able to find that studied bioavailability across a broad number of forms of magnesium in a monogastric animal (albeit, a rat).

What did they find?

The results are interesting with 2 very clear points made by the authors (Coudray et al) being:

  • There were no ‘major differences’ in the intestinal magnesium absorption between the 10 forms of magnesium studied.
  • All ten salts, whether they were organic or inorganic were equally efficient in restoring blood magnesium levels in plasma and red blood cells in rats.

They did however report that magnesium gluconate had the highest magnesium absorption and retention rate of all the products studied. Magnesium sulphate (commonly known as Epsom salts) and magnesium carbonate had both the lowest absorption and retention rates and this was confirmed by the fact these two supplement forms also had the highest faecal magnesium excretions.

Their results are summarised in the table below (Coudray et al 2005).

% Mg Absorption* % Mg Retention*
Magnesium Gluconate 57 36
Magnesium Citrate 50 34
Magnesium Chloride 49 35
Magnesium Oxide 48 34
Magnesium Pidolate  48  32
Magnesium Lactate  48  27
Magnesium Acetate  47  30
 Magnesium Aspartate  47  26
Magnesium Carbonate  44  22
Magnesium Sulphate  35  19

What does this tell us?

While this is only one study, it does serve to demonstrate, as the authors have noted, that all of these forms of magnesium are suitable and capable of restoring magnesium levels in magnesium deficient animals. It also means that blanket statements like ‘organic magnesium is more bioavailable than inorganic magnesium’ are not supported by this research as while 2 forms of organic magnesium were the most bioavailable, magnesium chloride and magnesium oxide were the 3rd and 4th most bioavailable according to this study.

Factors to consider before you choose a form of magnesium for your horse

Looking at these results only it would seem that magnesium gluconate or magnesium citrate would be the best forms of magnesium to use while magnesium chloride appears to be the most useful inorganic source of magnesium. However, there are the following factors you should consider:

  • How much magnesium is in the product – all of these various forms of magnesium contain different amounts of magnesium and therefore you would need to feed different amounts to achieve the required daily intake of magnesium. If for example you wanted to feed enough of one of these ingredients to add an additional 10 g/day of magnesium to a diet you would need to feed from as little as 17 grams of magnesium oxide to a huge 186 grams of magnesium gluconate (see the table below). Feeding the products like magnesium gluconate that contain only very small amounts of magnesium quickly becomes unpractical and will become expensive.
Form of magnesium % Magnesium Amount required to feed 10 g of Magnesium/day
Magnesium Gluconate 5.39 186
Magnesium Citrate 16.2 62
Magnesium Chloride 11.98 83
Magnesium Oxide 60.3 17
Magnesium Pidolate  8.6  116
Magnesium Lactate  10  100
Magnesium Acetate  11.3  88
 Magnesium Aspartate  7.49  134
Magnesium Carbonate  26.23  38
Magnesium Sulphate  9.9  101
  • Palatability – some sources of magnesium like magnesium chloride are notoriously unpalatable, so despite being a good source of magnesium from a bioavailability perspective, if you can’t get your horse to eat it, it isn’t going to help much. Magnesium sulphate is also well known as an unpalatable source of magnesium.
  • Cost – typically organic minerals are more expensive than inorganic minerals, so even though they might be slightly more bioavailable, they will be more expensive, even if their superior bioavailability is accounted for. For example, magnesium citrate is approximately $40/kg. To feed 5 grams per day of magnesium that is absorbed you would need to feed 62 grams of this supplement per day (based on the 50% bioavailability observed in rats). This would cost $2.48/day. Compare this to magnesium oxide at $10/kg. To feed 5 g/day of magnesium that is absorbed you would need to feed 35 grams per day which would cost 35 cents per day. So even though magnesium oxide is less bioavailable on a percent of magnesium absorbed basis, it costs less to feed the same amount of theoretically bioavailable magnesium.
  • Physical availability – some of these more obscure forms of magnesium are difficult to source, so even if they appear to be a good option for supplementation if you can’t access and purchase it easily, practically it isn’t going to work for you.

It is easy to get caught up in the bioavailability of minerals and to lose sight of the bigger picture. Always remember when assessing a mineral source to look at bioavailability together with these factors discussed above.

Magnesium Oxide

In taking all of these factors into account, magnesium oxide, which has been used as a magnesium supplement for humans and animals for decades is showing itself as an attractive option. Magnesium oxide is easy to source, cheap to buy, contains a lot of magnesium per kilogram, so you don’t need to feed a lot to achieve the level of magnesium you want in the diet and it appears to be readily absorbed in the small intestine.

However, you do need to be careful with the type of magnesium oxide you buy and use. Magnesium oxide is made via a process of calcination where a source of magnesium like magnesite or magnesium carbonate is burned at very high temperatures to produce magnesium oxide. The way the magnesium is calcined and its final particle size affect bioavailability, with product calcined at less than 800C or with a large particle size being less bioavailable. While selecting fine particle size product is relatively simple because you can see particle size to a large degree (ie fine powders versus granular forms), it is going to be difficult to know in some cases how well the product was calcined. My best suggestion is to purchase magnesium oxide from known manufacturers that produce magnesium oxide specifically for use in animal rations. ‘Causmag’ is an example of a company that does this.

Take home message

There is actually very little known about the bioavailability of magnesium in horses. Data in rats shows us that both organic and inorganic minerals are bioavailable and that both forms are capable of restoring blood magnesium levels in magnesium-deficient animals.

However, when you take into account the amount of each supplement you would need to feed to achieve the required daily magnesium dose, the cost of the different forms of magnesium, palatability and availability factors, magnesium oxide appears to be the most practical and cost-effective magnesium supplement available for use in horse rations.

When selecting magnesium oxide for your horses, use products from reputable companies known for producing magnesium oxide for use in animal rations and select the finest particle size product you can get.

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: 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


Understanding Protein Quality in Horse Feed

After energy, protein is the most important nutrient in a horse’s diet. Protein is needed to build good quality hoof, hair, skin, organ tissue, muscles, eyes, blood and bones. Protein is also a crucial part of enzymes and hormones and is an absolutely essential nutrient in a horse’s diet. After water, it’s the most plentiful substance in a horse’s body.

But as with many nutrients, ‘proteins ain’t proteins’. Some protein is of very high quality, other proteins can be so low in quality that they will seriously limit a horse’s ability to grow, reproduce, perform or build muscle. So what determines protein quality? First, let’s look at what proteins are.

What is protein?

Proteins are long chains of small molecules called amino acids. As a good analogy, think of amino acids as train carriages that join together with other amino acids to form a protein ‘train’. Amino acids, and therefore proteins, are organic compounds containing carbon, oxygen, hydrogen, nitrogen and sulphur.

The Amino Acid Puzzle

There are 21 amino acids which can be joined together in almost limitless combinations to form proteins. Up to 12 of these amino acids can be manufactured by the horse in its body, so they are known as non-essential amino acids. Under certain conditions like growth or illness, six of these non-essential amino acids must also be supplied in the diet. These ones are therefore known as ‘conditionally essential amino acids’. The remaining 9 amino acids are termed ESSENTIAL amino acids. These essential amino acids cannot be manufactured by the horse and must be supplied by the diet.

The 3 most limiting amino acids in the equine diet (meaning the amino acids that are likely to become deficient first and limit the horse’s ability to grow, reproduce, perform or build muscle) are lysine, threonine and methionine.

Protein quality

While it is possible, and even likely that horses do absorb some very high quality bacterial protein from their hindgut, a majority of a horse’s protein needs are met by what is fed in the diet. So the quality of protein you feed is extremely important.

Protein quality is determined by how well a particular protein meets a horse’s requirement for amino acids, and particularly the essential amino acids. In other words, a high quality protein will contain amino acids in very similar proportions to the amino acids a horse needs. Low quality proteins will either be too low in some of the essential amino acids to meet a horse’s requirement or they will contain essential amino acids that are not available for absorption, again making that protein unable to meet a horse’s requirement.

Selecting quality proteins?

Different feeds contain different levels of the essential amino acids and thus vary in ‘quality’. As a general rule, grass hay and pasture contains lower quality protein than legume hay and pasture like lucerne/alfalfa and clover. C4 type grasses also contain lower quality protein than C3 type grasses.

Cereal grains like oats, corn and barley contain lower quality protein than legumes such as soybean, lupins and beans. Co-products like copra meal sit in the middle with lower quality protein than legumes, but better quality protein than cereal grains. Of the commonly used protein ingredients in horse feed, heat treated cottonseed meal contains the lowest quality protein of all. Soybean contains the highest concentrations and best combination of many of the essential amino acids and is thus touted as the best quality vegetable protein available.

The absolute Rolls Royce of protein quality is whey protein. It has exceptionally high levels of essential amino acids that match almost perfectly a horse’s needs for protein. Just a small note of caution, if you wish to use whey protein in your horse’s diet, be sure to purchase ‘whey protein concentrate’ and not ‘whey powder’. Whey powder is only about 13% protein and contains over 50% lactose, making it unsuitable for use in equine rations.

Which horses need high quality protein?

Not all horses need very high quality protein in their diet. Dry or early pregnant mares and horses in good condition that are either not in work or only in light work have only moderate to low protein requirements that are generally easily met by average to good quality grass pasture and/or hay.

Growing horses, late pregnant and lactating mares, performance horses and any horse needing to build and maintain muscle mass do require high quality protein in their diet. These classes of horse will not do as well as they could unless high quality protein is supplied in the diet. Grass pasture or hay based diets will generally need to be supplemented with some legume hay or grain for the best results. This is why adding lucerne/alfalfa hay to the diet of horses needing to gain weight is recommended (see our post 7 simple steps for putting weight on your horse). The table below shows the % crude protein and g/kg of lysine in some common feed ingredients.

Name Crude Protein (%) Lysine (g/kg)
Whey Protein Concentrate 80 89.8
Soybean Meal 45 30.1
Soybean (Full Fat) 37 23.3
Canola Meal 37 21.1
 Faba (Tick) Beans  24  14.8
 Wheat Germ  23  14.7
 Cottonseed Meal*  36  14.7
 Lupins  28  13.3
 Linseed Meal  32  11.8
 Sunflower Meal  32  11.0
 Linseed  24  9.2
 Copra Meal  21  8.4
 Lucerne Hay  17  8.0
 Rice Bran  14  7.0
Palm Kernel Meal 17 6.4
 Millrun  15  6.3
 Wheat Pollard  14  6.3
 Wheat Bran  14  5.6
 Black Sunflower Seeds  29  5.1
 Soybean Hulls  12  4.7
 Sugarbeet Pulp  9  4.0
 C3 Type Grass Hay  11  3.8
 Barley  10  3.7
 Oaten Hay  8  3.0
 C4 Type Grass Hay  9  2.8
 Oats  8  2.8
 Wheaten Hay  8  2.8
 Corn (Maize)  10  2.8
 Rice (White)  8  2.7
 French White Millet  11  2.1
 Oat Hulls  4  1.8
* Heat treated cottonseed meal appears to have moderate levels of lysine, however during the oil extraction process, a toxic compound called gossypol binds itself to lysine, which means the gossypol is no longer toxic, but it does render the lysine indigestible, so digestible lysine levels are much lower than this.


Using FeedXL to monitor protein quality

The FeedXL Pro and Advisor plans include lysine as part of the nutrition analysis of a horse’s diet. Making sure that crude protein as well as lysine requirements are met in a diet will ensure your horse is getting the level of protein quality it needs.

If your diet is low in lysine, this indicates that the overall protein quality of the diet is low. In these situations, your horse’s ability to use the protein in its diet to grow, reproduce, build muscle or perform will be limited, even if crude protein requirements are met in the diet. If your horse’s diet does indicate lysine levels are too low, the following steps to increase lysine are recommended (in order):

  • Substitute some alfalfa/lucerne or clover pasture or hay for grass pasture or hay in the diet, adding up to 1 kg/100 kg of bodyweight (1 lb/100 lb bodyweight). In most cases, you will find this is enough.
  • If you use a complete feed, look for feeds that contain high quality protein legumes or if you mix you own feeds add legume grains like soybean, lupins or faba beans/tick beans/field beans to the diet. Avoid any feeds containing cottonseed meal or unnamed vegetable protein meals.
  • Small amounts of whey protein concentrate (or whey protein based products) can be used. For best effect in working horses, the whey protein should be fed within 15 minutes of the completion of exercise.

Lysine supplements are also available and can be used to boost lysine levels in your horse’s diet. You should however be aware that the level of lysine as shown by FeedXL in your horse’s diet is an indicator for overall protein quality in the diet. Increasing lysine by using legume hays or grains or whey means that along with lysine, you are also adding methionine, threonine and the remaining 6 essential amino acids. Adding purified lysine will certainly fill the specific lysine deficiency, but it may leave your horse with unquantified deficiencies of other essential amino acids.

Take Home Message

When looking at protein in your horse’s diet, always remember ‘proteins ain’t proteins’. Depending on their amino acid composition, some proteins are very high quality with good levels of essential amino acids while others are low in essential amino acids and therefore low in quality. The high quality proteins, including those from legume forages including lucerne/alfalfa and grains like soybean are able to support growth, pregnancy, lactation and muscle building, while low quality proteins like those from cottonseed meal and cereal grains will not be capable of properly supporting horses with large requirements for quality protein.

Not all horses require high quality protein, but if your horse is pregnant, lactating, growing or working hard and needing to build and maintain muscle mass the quality of protein in the diet will play a big role in determining how well your horse ‘performs’. Use FeedXL Pro to keep track of protein quality and to alert you when the diet is deficient.

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


Omega 3 for Horses: What, Why, How?

What is Omega 3?

‘Omega 3’ is a term used to describe a group of fatty acids that cannot be made by an animal. They are therefore classified as essential fatty acids because they must be consumed in the diet. There are three ‘Omega 3’ fatty acids; the ‘short chain’ alpha-linolenic acid (derived from plants) and the ‘long chain’ eicosapentaenoic acid (EPA) and docohexaenoic acid (DHA) (available almost exclusively from oily fish). Alpha-linolenic acid is the only form of Omega 3 present in a horse’s natural diet. This form of Omega 3 can be transformed (elongated) into EPA and DHA via a metabolic pathway in the horse’s body. EPA and DHA are the two biologically active forms of Omega 3.

What does Omega 3 do?

Omega 3 fatty acids are important constituents of all cell membranes. They are primarily needed for the production of eicosanoids, including leukotrienes (involved in inflammatory responses), prostaglandins (involved in smooth muscle contraction and inflammation), and thromboxanes (involved in blood clot formation). All cells in a horse’s body except the blood cells produce eicosanoids and the eicosanoids have their effect directly on the cell that produced them. They are highly potent chemicals and absolutely essential for the normal functioning of a cell.

Omega 3 fatty acids are also important in maintaining cell membrane structure and function as well as central nervous system development and immune function, plus they have a role in male fertility, affecting the shape, motility and concentration of sperm in seminal fluid.

Why is the Omega 6 to Omega 3 ratio important?

Omega 6 is another essential fatty acid. Omega 6 is present in equine diets as the ‘short chain’ linoleic acid (the plant form of Omega 6) which is then transformed (elongated) to the biologically active ‘long chain’ forms of Omega 6 known as dihomo-gamma-linolenic acid (DGLA) and arachidonic acid (AA). Both Omega 3 and Omega 6 are required in the equine diet. Omega 6, like Omega 3 is an important constituent of cell membranes and plays a critical role as a precursor for the eicosanoids (leukotrenes, prostaglandins and thromboxanes) that control swelling, inflammation, clotting and dilation.

The reason the Omega 6 to Omega 3 ratio is important is the plant derived Omega 3 fatty acids and Omega 6 fatty acids share a common enzyme in the first step of the metabolic pathway they need to travel to be ‘elongated’ into the long chain forms of Omega 3 and 6 fatty acids (which are then used to produce physiologically active prostaglandins).

Omega 3 fatty acids are first elongated to EPA and then EPA is turned into what are termed ‘series 3 prostaglandins’. Omega 6 fatty acids are elongated to DGLA which is then turned into ‘series 1 prostaglandins’ or AA which leads to the production of ‘series 2 prostaglandins’.

The first step in the elongation of Omega 3 and 6 fatty acids requires an enzyme called Delta-6 Desaturase (D6D). If there is too much Omega 6 present in the cells where prostaglandin production is occurring, the Omega 6 will ‘outcompete’ the Omega 3 fatty acids for this enzyme. The result being overproduction of the Omega 6 derived prostaglandins and not enough of the Omega 3 derived prostaglandins. The Omega 3 prostaglandins tend to have an opposing or modulating effect on the Omega 6 derived prostaglandins (Omega 3 derived prostaglandins aren’t necessarily anti-inflammatory, but they are less inflammatory than their Omega 6 relatives). The ultimate effect of too much Omega 6 in a diet is increased inflammation, increased risk of blood clotting and constriction of blood vessels.

Interestingly, phenylbutazone’s (Bute) mode of action is to block these same pathways, preventing Omega 6 fatty acids from being transformed into pro-inflammatory prostaglandins.

With the competitive nature between Omega 3 and Omega 6 and the consequences of a diet too high in Omega 6, the ratio of Omega 3 to Omega 6 in any animal’s diet (including our own) is extremely important.

Other nutrients including biotin, vitamin E, zinc, vitamin B12 and vitamin B6 are also reportedly required to allow the efficient transformation of alpha-linolenic acid to EPA and DHA.

What is the recommended Omega 6: 3 ratio in a horse’s diet?

To date there is no established ratio of Omega 6: Omega 3 in a horse’s diet. However, if we look at the diet horses evolved to eat, being primarily grasses and herbs, we can start to hypothesise that horses should have a diet that contains more Omega 3 than Omega 6. I would suggest at the very most a horse’s diet should contain 1 part Omega 6 to 1 part Omega 3.

How much Omega 3 and Omega 6 are in common horse feeds?

Forages contain more Omega 3 than Omega 6 while grains contain more Omega 6 than Omega 3. Some oilseeds like sunflowers contain more than 200 times as much Omega 6 as Omega 3 while other oilseeds like linseed (flax) contain close to 3.5 times more Omega 3 than 6. A detailed breakdown of the amount of Omega 3 and 6 in common horse feeds is shown in the table below (data from Premier Nutrition).

Ingredient Name Omega 3 (%) Omega 6 (%) O6: O3 Ratio
Pasture (3.5% Crude Fat)* 1.8 0.6 0.3: 1
Grass Hay 1.0 0.3 0.3: 1
Alfalfa/Lucerne Hay 0.5 0.4 0.7: 1
Oats 0.1 2.4 19.5: 1
 Corn/Maize  0.03  1.9  55: 1
 Barley  0.1  1.1  9.1: 1
 Rice Bran  0.2  6.6  37: 1
 Wheat Bran  0.2  2.1  11.6: 1
 Sunflower Seeds  0.13  27.1  206: 1
 Full Fat Soybean  1.4  9.8  7.2: 1
 Soybean Meal  0.1  1.0  7.2: 1
 Lupins  0.7  1.5  2: 1
 Faba Beans  0.1  0.9  12.8: 1
 Copra Meal  0  0.2  N/A
 Canola Meal  1.1  2.2  2.0: 1
 Sugarbeet Pulp  0.04  0.2  5.8: 1
 Soybean Hulls  0.2  1.1  7.2: 1
 Brewers Grains  0.2  2.2  9.3: 1
 Dried Distillers Grains (maize)  0.1  3.8  55.4: 1
 Linseed (Flax) Whole  19.1  5.6  0.3: 1
 Linseed Meal  4.5  1.3  0.3: 1
 Coconut Oil  0.1  2.0  20: 1
 Cod Liver Oil  24.5  2.0  0.1: 1
 Canola Oil  9.8  19.5  2: 1
 Soybean Oil  7.2  51.7  7.2: 1
 Sunflower Oil  0.3  60.5  206: 1
 Corn Oil  0.9  55  55: 1
 Olive Oil  0.7  10.8  15.7: 1
 Linseed (Flax) Oil  57.4  13.9  0.24: 1

* Data from Mel’uchova et al (2008)

Diets primarily based on forages that don’t use large amounts of oils like corn or sunflower oil should contain more Omega 3 than Omega 6. Diets that contain a moderate to large amount of grain and small amounts of forage (like the typical racehorse diet) will almost certainly contain far more Omega 6 than Omega 3.

Is there research to support the use of Omega 3 fatty acids in horses?

Most of what we know about omega fatty acids is derived from research in other animal species including humans. There is however some equine research that does lend support to supplementing diets with Omega 3 fatty acids. In a study that used 16 horses with arthritis, Manhart et al (2009) reported that horses supplemented with DHA and EPA experienced a greater decrease in joint fluid white blood cell counts and lower plasma prostaglandin E2 levels (an Omega 6 derived prostaglandin which is a pro-inflammatory pain producer and plays a major role in osteo-arthritis. It is this prostaglandin that many non-steroidal anti-inflammatory drugs block the production of to reduce pain and inflammation).

A study published in the Canadian Journal of Veterinary Research in 2002 (O’Neill et al) looked at the ability of flaxseed to reduce the inflammation associated with culicoides (midge) hypersensitivity (sweet itch or Queensland itch). These researchers reported that feeding 1 lb of flaxseed per 1000 lb of bodyweight to horses (or 0.5 kg per 500 kg bodyweight, equivalent to 3.5 oz or 100 ml of flaxseed oil) over a period of 42 days reduced inflammation and the size of the area that reacted to culicoides extract which was injected into the skin. In contrast to this study however, Friberg et al (2002) reported that horses supplemented with either 200 ml/day of flaxseed oil or 200 ml/day of corn oil showed no difference in the lesional surface area associated with culicoides allergy or the number of times horses itched. O’Neill et al believe the difference between the results reported by these two studies may lie somewhere in the fact they used whole flaxseed and not just the extracted oil. Unfortunately the omega 6 to omega 3 ratio was not reported in these studies. Horses in the Friberg et al study were maintained on ‘pellets’ so it is possible that their dietary Omega 6 ratio was too high for 200 ml of flax oil to have a noticeable benefit. It was noted in this study that a miniature horse receiving the full 200 ml dose responded particularly well to the supplement which may indicate that the dose for the larger horses needed to be much higher to have a significant benefit.

Brinsko et al (2009) studied the sperm quality in 8 stallions when they were fed their normal diets with or without a DHA-enriched supplement. This study found no difference in fresh sperm quality, however, as the semen was cooled and stored, sperm quality tended to be better when the stallions were supplemented with DHA. Most of the improvements observed however were not statistically significant (which means they may have just happened by chance and may not actually be due to the supplement).

Pagan et al (2010) reported that supplementation with 60 ml of fish oil significantly increased serum and red blood cell EPA and DHA while supplementation with 60 ml of corn oil significantly reduced red blood cell EPA levels. Pagan et al (2012) have also reported improved insulin sensitivity in horses supplemented with omega 3 fatty acids from fish oil.

When should you supplement?

If your horse’s diet contains a moderate to large amount of grain or high Omega 6 oils like corn or sunflower oil you may need to consider adding additional Omega 3 to the diet to keep the ratio of Omega 6 to Omega 3 at or preferably below 1: 1. Take the following diets as examples:

Diet 1 – High in Omega 3

10 kg/day (22 lb) Pasture
2 kg/day (4.4 lb) Alfalfa/Lucerne Hay
0.5 kg/day (1.1 lb) Oats
200 g/day (7 oz) Sunflowers
100 g/day (3.5 oz) Vitamin and Mineral Supplement

This diet will contain an Omega 6 to Omega 3 ratio of 0.4: 1 and does not need additional Omega 3 supplementation. The diet is however still higher in Omega 6 than a 100% forage based diet so some Omega 3 supplementation may be warranted in certain situations, for example if the horse is arthritic.

Diet 2 – High in Omega 6

2 kg/day (4.4 lb) Pasture
4 kg/day (8.8 lb) Alfalfa/Lucerne Hay
3 kg/day (6.6 lb) Oats
2.5 kg/day (5.5 lb) Corn/Maize
250 g/day (9 oz) (5.5 lb) Sunflowers
250 ml/day (9 floz) Corn Oil
100 g/day (3.5 oz) Vitamin and Mineral Supplement

This diet will contain an Omega 6 to Omega 3 ratio of 3.5: 1 and would benefit from additional Omega 3 supplementation. Adding 400 ml of linseed oil to this diet will lower the Omega 6 to Omega 3 ratio to 1: 1 and also allow for some of the high Omega 6 grain to be removed from the diet.

At this point in time there is no easy way to calculate your horse’s dietary Omega 6 to Omega 3 ratio. We will be incorporating this feature into FeedXL as soon as we can. The greatest challenge is going to be gathering the information needed for all of the commercially produced feeds.

How should you supplement?

There are various ways to add additional Omega 3 to diets. The best known Omega 3 supplement for horses is linseed (flax) oil. Linseed oil is 57% Omega 3, making it a useful Omega 3 supplement. Freshly ground linseed can also be used (read FeedXL Newsletter # 22 Feeding Flaxseed). Linseed meal will have very little effect on a diet’s overall Omega 6 to 3 ratio as even though linseed meal does contain more Omega 3 than 6, the amount of Omega 3 in linseed meal is so small it really won’t influence the overall diet’s Omega fatty acid ratio. Commercial Omega fatty acid supplements are also available and these now often contain fish oil to provide a direct source of DHA and EPA in the diet.

Of course the best way to maintain a balanced Omega 6 to 3 ratio in your horse’s diet is to maintain them on a largely forage based diet and only use grains and oilseeds like sunflower seeds in moderate to large amounts where absolutely necessary.

Take Home Messages

  • Diets that contain a lot of grain or high Omega 6 oils like corn or sunflower oil may cause your horse’s diet to contain more Omega 6 than Omega 3 fatty acids.
  • Too much Omega 6 in a horse’s diet interferes with the body’s use of Omega 3 fatty acids. This imbalance could lead to excess inflammation and problems like arthritis.
  • To help modify the inflammatory reaction of a horse’s body to stimuli like exercise, the Omega 3 to 6 ratio needs to be kept in balance.
  • Omega 6 is just as important in the diet as Omega 3, they just need to be kept in balance with one another.
  • There is no established ratio of Omega 6 to Omega 3 for horses, however a horse’s natural diet contains more Omega 3 than Omega 6, so keeping your horse’s diet ratio at 1: 1 or less is logically what will be best.
  • FeedXL currently doesn’t calculate your horses Omega 3 to Omega 6 ratio, however given the importance of this aspect of equine nutrition, this is a feature we are now working on implementing.

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


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