It occurs in susceptible horses and ponies when phototoxic or photoactive substances accumulate in the skin and interact with sunlight. This can result in severe itchy, crusty and often painful dermatitis. It generally occurs in non-pigmented (i.e. white) skin and skin with little hair cover (such as the muzzle, eyelids, ears and coronary bands).

Equine photosensitivity may be caused by the ingestion of plant or fungal products, chlorophyll metabolites, or other chemicals. It can also occur in conjunction with the use of some medications.

Effects of ingestion of the offending substance may be cumulative and a horse may not develop signs of photodermatitis immediately.

Using lucerne/alfalfa or clover as an example, horses may not develop any clinical signs of photosensitisation until weeks after initially consuming the hay, chaff or pasture which is causing the reaction. We can be feeding our horses this feedstuff for quite some time without any issues, before seemingly all of a sudden, photodermatitis occurs. This can be difficult and confusing, as we often expect clinical signs to appear immediately or very soon after consumption of the offending feed. This can lead to constantly changing our horse’s feed, in attempt to identify the culprit. As a result, this may significantly increase a horse’s risk of developing colic or laminitis.

Other recognised potential causes of photosensitisation include gluten sensitivity; reactions to drugs such as tetracycline antibiotics and phenothiazine tranquillisers; exposure to certain chemicals; and consumption of pastures rich in phosphorus fertilisers.

These are commonly overlooked, but in the author’s experience, generally contribute to photosensitivity reactions more commonly than consumption of lucerne/alfalfa and clover alone, which are often thought to be culprits.

Photosensitisation may also occur as a result of impaired liver function in a horse (known as secondary photosensitivity/photosensitisation).

For these reasons, the effective prevention and treatment of photosensitisation should involve thorough analysis of diet, management, pasture, supplement and medication use in susceptible horses. In many cases, there may be more than one factor contributing to photosensitisation.

The complexity of the condition can also help to explain why simply applying topical creams or lotions and/or simply removing lucerne/alfalfa from the diet or adding a mycotoxin binder to our horse or pony’s feed often doesn’t provide a long-term or effective solution.  Removing certain feeds from a diet can also contribute to nutritional insufficiencies or deficiencies, which can sometimes further compound the problem.

It is critically important to address the underlying cause(s) of the photosensitivity if we want treatment to be effective and to prevent recurrence.

Optim Equine

Camilla Whishaw is a highly regarded, experienced horsewoman and naturopath, helping to holistically treat and manage a broad range of equine health conditions and injuries, with a passion for mare and stallion fertility.

As a world-renowned practitioner, presenter, author, and consultant in the field of Equine Naturopathy, Camilla shares her knowledge through keynote presentations, interviews, lectures, panel sessions, and workshop training.

The availability and use of antimicrobial herbal and pharmaceutical medicines gives us the ability to help our equines live longer, healthier lives. If we want this to continue, however, we need to be incredibly judicious in how we use these treatments.

Antimicrobial Resistance (AMR) occurs when bacteria, viruses, fungi and parasites no longer respond to antimicrobial agents. Using antimicrobial drugs inappropriately or unnecessarily increases AMR. This means that antibiotics and other antimicrobial agents become ineffective in helping our horses in conditions they were once effective in helping to resolve.  This can mean that when our horses actually genuinely need such medications to help, our options are more limited.

The largest contributor to AMR is overuse and misuse of antimicrobial agents. It can be quite easy to accidentally fall into the trap of using such medications without stopping to give thought to what we are actually doing. For example, we give our horses antibiotics unnecessarily, such as in the case of a horse with a snotty nose (viral infection), which we want to ‘treat’ with antibiotics. Antibiotics are ineffective in the case of viral infections. Or when we routinely deworm our horses on a seasonal basis as opposed to employing strategic deworming, faecal egg sampling and pasture management methods (for example regularly picking up manure, harrowing and/or rotating paddocks). To learn more about deworming, see the article: Drenching/Deworming with Panacur.

In some parts of the world (such as Australia and New Zealand), the use of feed supplements that contain antibiotics is a real concern. An example of this is a product which claims to assist in helping prevent laminitis (claims which are not supported in many other parts of the world) Laminitis ‘Prevention’- But at what cost? Even something as innocent as using anti-fungal washes on any skin condition that we may see on our horses and ponies increases the risk of AMR.

Starting with sound animal husbandry practices such as feeding our horses well-balanced diets which meet key nutrient requirements Nutrient Requirements for Horses: Fortified Feeds and the need for Supplementation; employing good pasture management and stable hygiene practices; avoiding self-prescribing for our horses ‘just-in-case’; and disposing of unused antibiotics and anti-fungals appropriately are all really good places to start to help reduce AMR.

In many instances, appropriately applied and selected nutritional supplements and herbal medicines can be used to effectively prevent, treat or manage health challenges in our equines: sometimes used as stand-alone therapies, other times used in conjunction with standard medications. In both cases, they can help to significantly reduce AMR.

We can also be mindful not to pressure our vets to prescribe medications when they don’t feel it is necessary for our horses and ponies. This is in the best interests of not only our equines, but all animals and humans for the long term.

Optim Equine

Camilla Whishaw is a highly regarded, experienced horsewoman and naturopath, helping to holistically treat and manage a broad range of equine health conditions and injuries, with a passion for mare and stallion fertility.

As a world-renowned practitioner, presenter, author, and consultant in the field of Equine Naturopathy, Camilla shares her knowledge through keynote presentations, interviews, lectures, panel sessions, and workshop training.

In short, it relates to the microbiota of our equines’ digestive systems.

The bacteria, fungi, protozoa, and viruses that colonise the equine gastrointestinal tract (GIT) (collectively known as the microbiota), play many crucial roles in horse health.

These microbes influence digestion, energy and nutrient production, immune health, levels of inflammation in the body, overall GI health, body condition, respiratory health, skin health, metabolic health, reproductive hormones and the production of neurotransmitters (chemicals which influence their mood, temperament, learning, motor control and behaviour).

When the microbiota deviates away from what is optimal, a horse is more susceptible to conditions of inflammation, illness, pathology, GI disturbances including colic, gastric and colonic ulcers, stressed behaviour and diminished nutrient and energy production and uptake.

The large population of microbes that inhabit the equine GI tract are influenced by what our horses and ponies eat. The specific types of microbes become accustomed to what our equines are fed and must adapt to different types of feed. This means that when they eat different types of feed, there are different populations and types of microbes.

Sudden dietary changes induce rapid shifts in this delicate balance of microbes and the byproducts they produce, rendering a horse more susceptible to illness. Whilst this is a broad simplification, the sudden changes in the microbes and their activity are largely indicated in many cases of colic, laminitis and other serious health conditions.

When we add new feeds to a diet or change a horse’s diet- we want to facilitate a gradual change in the microbial population and the products these microbes produce. The best way to do this is to introduce new feeds into their diet gradually over a 7-14 day period, slowly increasing the amounts of the new feed as the microbial population adjusts.

It’s a simple process, which is largely overlooked: something which can save a lot of pain, heartache and expense.

Optim Equine

Camilla Whishaw is a highly regarded, experienced horsewoman and naturopath, helping to holistically treat and manage a broad range of equine health conditions and injuries, with a passion for mare and stallion fertility.

As a world-renowned practitioner, presenter, author, and consultant in the field of Equine Naturopathy, Camilla shares her knowledge through keynote presentations, interviews, lectures, panel sessions, and workshop training.

What is Protein?

Protein is a crucial macronutrient in a horse’s diet and is comprised of long chains of building blocks called amino acids. There are 21 amino acids. The specific order and combination of amino acids determines the structure and function of each protein. Insufficient dietary intake of specific amino acids limits the production of key proteins essential in our horse’s bodies. For more in-depth information on protein quality see the article: Soy: The Good, Bad and Confusing.

Protein is Needed for Growth, Maintenance and Repair of Tissue

We commonly only think of this as important when we are trying to increase muscle mass in a horse. For instance, building top-line on our ridden horse, or conditioning a thoroughbred yearling for sale. Yet protein is absolutely essential for normal growth and development of the young horse, and recovery from riding and training in active horses. Insufficient protein in the diet can therefore increase risk of illness and injury in our horses. Times of illness and injury also increase protein requirements in order to help recover from the illness or heal from the injury. Providing insufficient protein to a sick or injured horse during their recovery can significantly delay and/or impair their healing and adversely impact their future athletic potential.

Protein Facilitates Biochemical Reactions

Enzymes are a specific type of protein that aid in the normal biochemical reactions that take place in a horse. Specific enzymes are needed to facilitate proper digestion (therefore helping to promote optimal gut health and utilisation of feed); energy production (helping a horse to perform); normal metabolism (helping to regulate weight and temperature in a horse); blood clotting; and muscle contraction. Insufficient protein in the diet can lead to digestive problems- a critical consideration given the heightened focus on gastrointestinal (GI) health. A common mistake is to restrict protein intake in the overweight horse: this can further slow metabolism (compounding the problem) and compromise overall health.

Protein is Required for Proper Communication in the Body

Hormones are chemical messengers that aid in communication between a horse’s cells, tissues and organs. They are needed for everything from normal growth, metabolism, reproductive function and digestion. Amino acids are also an important component of neurotransmitters: the chemical messengers which play a crucial role in a horse’s mood, temperament, learning and behaviour.

Protein Provides Structure

Different types of protein are essential for the formation of healthy bones, tendons, ligaments, muscles, skin and hooves. Depending on the type of protein, they aid in providing structure, strength, elasticity and rigidity to specific tissues. Insufficient protein in the diet can make a horse more susceptible to injury to muscles, tendons, bones and ligaments. They may also have poor skin and/or hoof quality.

Protein Helps to Maintain pH Balance in the Body

Proteins act as a buffer system, helping a horse’s body to maintain proper pH values of the blood and other bodily fluids.

Protein Helps to Balance Body Fluid Levels

Albumin and globulin are two important proteins found in a horse’s blood. They help to maintain the body’s fluid balance by attracting and retaining water. If a horse’s diet has consistently has low quantities of quality protein, the levels of albumin and globulin eventually decrease. This can result in swelling or oedema as these proteins can no longer keep blood in the blood vessels, forcing the fluid into the spaces between cells. The irony is that protein is often blamed for causing swelling in horses- with the reverse often being the cause!

Protein is Needed for a Healthy Immune System

Protein is absolutely essential for white blood cell production and the formation of immunoglobulins (antibodies) needed to fight infection in our horses. Insufficient protein in the diet can leave a horse more susceptible to bacterial, viral and fungal infections.

Protein Aids in the Transportation and Storage of Nutrients

Transport proteins carry substances in our horse’s blood streams- into, out of and within cells. The substances transported by these proteins include nutrients such as vitamins and minerals, blood sugar, cholesterol and oxygen. Whilst we often think of iron as being a key driver in helping oxygen delivery to the body’s tissues, protein plays a paramount role- yet is often overlooked. Specific proteins also have a storage role: ferritin is a storage protein that stores iron.

Problems with Excessive Protein: Myths or Facts?

So now we can see that protein is absolutely vital in keeping our horses healthy, yet is there a downside to this nutrient? And can we feed too much? Like most things, the answer is relative to the situation and the individual horse.

Excess Protein

To overly simplify, horses are unable to store excess protein that they consume in their diet for later use. The metabolism of excess protein increases levels of nitrogen end-products, such as ammonia and urea. A diet containing excess protein will increase the horse’s water requirements and urine output as the ammonia and urea are flushed out of the body. If a horse is kept out at pasture, is only in light work and has free access to plenty of fresh water, this generally isn’t a problem. It is an issue however where horses are stabled. Exposure to this strong urine can cause lung irritation and other respiratory problems. Extra urination means extra wet bedding, which equates to more mucking out.

Metabolism of Protein Produces Heat

Protein digestion and metabolism is a heat generating process. A horse that is on a high protein diet that is burning a lot of protein as an energy source will sweat more to help get rid of the heat. It is important to remember that the body has a preference for using carbohydrates and fats over protein as an energy source, and will only use protein as a significant energy source when these other two nutrients don’t meet their requirements. Protein fed in appropriate amounts to meet a horse’s needs will not contribute greatly to heat production or sweating. Feeding excessive amounts of protein however, particularly to horses in hot and humid climates, or those undertaking moderate to heavy work, can contribute to dehydration and heat stress.

Protein Causes Poor Behaviour/ Hot Horses: MYTH

Protein is often blamed for making horses ‘hot’, nervy or spooky. This is turn can cause some owners to avoid including quality sources of protein in their horse’s diet. Protein has not been shown to cause behavioural issues in horses. Diets which are high in energy and excessive to a horse’s energy needs which are also high in protein can contribute to a horse being hyperactive or silly. The problem here is the overall energy intake, not the protein!

Kidney and/or Liver Damage: MYTH

In healthy horses, high protein diets have not been demonstrated to cause kidney and/or liver damage. In horses that have pre-existing liver or kidney problems, then protein intake may need to be restricted- ensuring that intake is still sufficient to meet a horse’s daily requirements but does not exceed them.

Take Home Message

As a general rule, I see far more horses in clinical practice with insufficient protein intakes compared to those with excessive protein intakes. Insufficient protein in the diet may leave a horse more susceptible to illness and/or injury and delay or impair their recovery. Including adequate, quality protein in the diets of our horses is absolutely essential in order for them to be healthy, perform and recover at their best.

Optim Equine

Camilla Whishaw is a highly regarded, experienced horsewoman and naturopath, helping to holistically treat and manage a broad range of equine health conditions and injuries, with a passion for mare and stallion fertility.

As a world-renowned practitioner, presenter, author, and consultant in the field of Equine Naturopathy, Camilla shares her knowledge through keynote presentations, interviews, lectures, panel sessions, and workshop training.

For the purpose of this article, we will focus on soy bean meal and feeds containing processed soy- not soy oil or soy bean hulls- as these components alone have significantly different nutritional value and properties.

Pros

Soy is one of the more widely fed significant sources of protein in a horse’s diet. It is a common misconception that protein is only needed to promote weight gain, muscle condition or the development of topline. Whilst it is important in these instances (in combination with appropriate exercise and training), protein is absolutely essential for a multitude of functions in all horses at any life stage and exercise level: it is a critical component of normal immune function; facilitates proper growth and repair of the musculoskeletal system; and is needed for the majority of metabolic processes in the horse. Even horse’s who aren’t in heavy work and/or actually need to lose weight need sufficient protein in their diet.

Protein is comprised of smaller units called amino acids. Horses require 21 amino acids, 12 of which a horse can synthesise (produce) themselves. The remaining nine (and in the case of illness or injury- potentially ten) amino acids must be present in a horse’s diet. These are known as ‘essential amino acids’. In addition to all essential amino acids being present in the diet, they must be present in appropriate quantities- so a horse has enough of each of them to facilitate various bodily functions. If they fall short of any essential amino acids then health, normal development, performance and recovery may be compromised.

With the exception of oils, practically all horse feeds, grains and forages contain SOME protein- Depending on the exact feed source, the actual amounts of protein contained in these feeds will vary. Different sources of protein are comprised of different sequences of amino acids. This influences how useful they are to a horse. Some high protein feed sources are actually of little value to a horse, as they lack decent amounts of essential amino acids that a horse needs, or they are unable to be properly digested and absorbed by a horse.

So how does all this relate to soy? Soy is one of the best dietary sources of lysine for our horses and ponies. Lysine is a very important essential amino acid in the equine and it is generally one which is lowest in our horse’s diets. Lysine is absolutely essential for normal muscle growth and turnover, helps to promote collagen integrity (important for healthy bones, skin, muscles, tendons and ligaments), is critical for proper immune function, and may further help bone health through improving calcium absorption and utilisation. Animal studies have also shown that diets low in lysine may be associated with anxiety. Thus, a diet low in lysine may be one of many potential contributing factors in some cases of horses with an anxious tendency.

For horses competing in endurance events, optimising hydration pre-event is an important consideration. Commercial soy feed products which require soaking before being fed, can help to increase fluid intake in horses. It’s important to keep in mind that there are other feeds which can be used for this same purpose. Soy is not the only option.

Being a low starch and protein rich feed, processed soy meal can aid in stabilising blood glucose levels- thus helping to prevent rapid spikes in insulin levels. High insulin levels are a driving factor of equine metabolic syndrome and are commonly implicated in many cases of laminitis. Horses with Pituitary Pars Intermedia Dysfunction (PPID) (also commonly referred to as ‘Cushings’) and Polysaccharide Storage Myopathy (PSSM)- a component in many cases of ‘tying up’, may also particularly benefit from a diet low in starch and containing adequate quantities of quality protein.

The phytoestrogen content of soy is an important, yet often misunderstood concept. Soy is unique in that it contains a high concentration of isoflavones, a type of plant oestrogen (phytoestrogen) that is similar in function to the hormone oestrogen but with much weaker effects. Soy isoflavones can bind to oestrogen receptors in the body and can either increase or decrease oestrogen levels in the body. Research has demonstrated that when oestrogen levels in the body are naturally low, then ingestion of phytoestrogens may help to increase the body’s levels.  When oestrogen levels in the body are naturally high, then consuming phytoestrogens may help to reduce oestrogen levels, as they bind to some of the receptor sites that naturally produced oestrogen may bind to.

Potential Cons

The phytoestrogen activity of soy may also potentially be a drawback of this feed. Excessively high intakes of phytoestrogens have the potential to decrease testosterone levels, an important consideration in stallions and colts. Soy certainly isn’t the only source of phytoestrogens commonly found in horse diets: clover grass is rich in phytoestrogens. Before attributing potential positive or negative effects of phytoestrogens in a horse’s diet, the total quantity of all phytoestrogen rich food sources needs to be taken into account.

Soy is commonly attributed to causing allergic symptoms in horses- everything from itchiness and skin irritation, colic and digestive disturbances, to overly-reactive behaviour and respiratory issues. Whilst soy is a common allergen in humans, the same has not yet been demonstrated in horses. Diagnostic tests for equine food allergies are difficult to carry out, time-consuming and often unreliable. In clinical practice, I find that the majority of horses with allergy related symptoms (whether these be environmental or food related) improve significantly when overall nutritional status and specific components of both immune and gut health have been therapeutically addressed. Generally something which may appear to cause allergic symptoms in a horse is not the real culprit.

A significant valid concern with soy is the fact that it is one of the most commonly genetically modified (GM) crops. Whilst this is only an issue in some parts of the world, it is certainly worth taking into consideration. Animal studies with GM foods indicate that they may cause some common toxic effects such as hepatic, pancreatic, renal, or reproductive effects and may alter blood parameters and immune function.

Soy is high in omega six fatty acids. Whilst these types of fatty acids are an essential component in our horse’s diets, they are generally present in higher than desirable amounts. Of further importance is the percentage of omega six fatty acids in proportion to omega three fatty acids. High levels of omega six fatty acids with accompanying low levels of omega three fatty acids are known to promote inflammation. Adding large amounts of soy products to a diet already high in omega six fatty acids further accentuates the shift towards a pro-inflammatory tendency. This can  have wide-ranging effects from impairing recovery from training, competition and exercise; compromising immune function; and exacerbating already existing inflammatory conditions such as osteoarthritis, desmitis, placentitis and laminitis to name a few.

Uncooked or even inadequately cooked soybean meal has some anti-nutritional factors. Trypsin inhibitor is the most significant one. Trypsin is an essential enzyme which helps horses to properly digest protein, allowing for absorption and metabolism of the amino acids which make up the protein. Trypsin inhibitor found in uncooked soybean prevents trypsin from being able to properly break down proteins. This means that in the presence of trypsin inhibitors a large percentage of all protein from all sources a horse is consuming is unable to be properly digested, absorbed and metabolised.

Some concerns exist that soy can have a negative effect on thyroid function and can alter the levels of thyroid hormones. Whilst the majority of data is from human studies, it is unlikely that regular consumption of small amounts of soy containing foods have significant impact on thyroid function in healthy subjects. In cases where hypothyroidism already exists (keeping in mind that diagnosis and true cases of hypothyroidism in horses is rare), then reviewing the appropriate feeding of soybean containing products is warranted.

Conclusion

Processed soybean meal and feeds containing this product can be a valuable inclusion in the diets of many horses. Factors which may caution against the feeding of soy to some horses include specific health concerns and where in the world the soy is grown and produced. Soybean meal MUST be properly heat treated to prevent trypsin inhibitor from interfering with protein digestion. The quantity of soy products fed and the overall diet of the horse are crucial factors to take into consideration.

Rarely is anything inherently good or bad: the same may be said of soybean products. The most important consideration is that one size doesn’t fit all: feed the individual horse in front of you!

Optim Equine

Camilla Whishaw is a highly regarded, experienced horsewoman and naturopath, helping to holistically treat and manage a broad range of equine health conditions and injuries, with a passion for mare and stallion fertility.

As a world-renowned practitioner, presenter, author, and consultant in the field of Equine Naturopathy, Camilla shares her knowledge through keynote presentations, interviews, lectures, panel sessions, and workshop training.

The condition is caused by biting midges or gnats (Culicoids). It’s not the actual bite that causes the reaction, but rather the insect’s saliva. Whilst this may not affect some horses, other horses are abnormally sensitive to the midge saliva. 

There are many different species of Culicoides, and although their activity is commonly seasonal, in some regions, they are active year round.

In those horses with sensitivities to Culicoides, there are two types of commonly recognised allergic responses: Type 1 which is an immediate reaction, often resulting in hives; and Type 4, which is a delayed reaction. The reactions are mediated by different chemicals in the body. Horses can experience both Type 1 and Type 4 reactions.

Those horses who experience hypersensitivity reactions to Culicoides are commonly atopic, referring to their genetic tendency to develop various allergic conditions, with heightened immune responses. This in part explains why simply applying various lotions and medications to help ‘treat’ the symptoms are merely a ‘band-aid’ effect as they do not address the underlying atopic cause. 

Atopic conditions are associated with imbalances in T helper 2 and T helper 1 cells (important cells of the immune system).

Whilst minimising exposure (as is feasibly practical) is important, correctly employed ingestive herbal and nutraceutical supplements, used under qualified and experienced guidance can play an incredibly valuable role by regulating T helper 1 and T helper 2 cell balances, thereby helping horses with such sensitivities.

Skin conditions are so often more than skin deep, and without addressing the underlying cause, results will only ever be superficial….

Optim Equine

Camilla Whishaw is a highly regarded, experienced horsewoman and naturopath, helping to holistically treat and manage a broad range of equine health conditions and injuries, with a passion for mare and stallion fertility.

As a world-renowned practitioner, presenter, author, and consultant in the field of Equine Naturopathy, Camilla shares her knowledge through keynote presentations, interviews, lectures, panel sessions, and workshop training.

Research strongly suggests that selenium may help to prevent tying-up in certain cases. When prescribed appropriately, selenium has been demonstrated to improve performance, stamina and muscle strength in the equine.

Australian soils and pastures are generally low in selenium, particularly those that are: acidic or sandy; have a high clover content; have heavy or long-term fertiliser application; have high amounts of rainfall.

Many people are unaware that an excess intake of selenium is extremely toxic. Whilst soils and pastures may be low in this nutrient, the widespread use of fortified feeds and supplements ‘self-prescribed’ by well meaning owners to their horses may result in inadvertent over-dosing.

Supplementation of any nutrient should be strategic and well indicated, encompassing a holistic approach. Be smart…. seek professional advice to OPTIMise your horse’s health…

Optim Equine

Camilla Whishaw is a highly regarded, experienced horsewoman and naturopath, helping to holistically treat and manage a broad range of equine health conditions and injuries, with a passion for mare and stallion fertility.

As a world-renowned practitioner, presenter, author, and consultant in the field of Equine Naturopathy, Camilla shares her knowledge through keynote presentations, interviews, lectures, panel sessions, and workshop training.

Within each leaf of the plant is a gel which helps to increase healing rate (by promoting cell proliferation) and decrease inflammation when applied to wounds and burns. Studies have also shown aloe vera gel to have antibacterial and anti fungal effects and to reduce swelling associated with insect bites.

Using fresh aloe vera gel is best (most commercial products contain artificial preservatives, many have colourants added, and the beneficial therapeutic compounds of the plant may only be in small amounts if at all!). The good news is even those who aren’t green thumbs can easily grow aloe vera in a pot at home!

Fresh aloe vera gel can be obtained by splitting a leaf and applying the green tinged clear jelly inside of the split leaf to cuts, wounds, fungal infections, burns and insect bites.

Optim Equine

Camilla Whishaw is a highly regarded, experienced horsewoman and naturopath, helping to holistically treat and manage a broad range of equine health conditions and injuries, with a passion for mare and stallion fertility.

As a world-renowned practitioner, presenter, author, and consultant in the field of Equine Naturopathy, Camilla shares her knowledge through keynote presentations, interviews, lectures, panel sessions, and workshop training.