Was it Something He Ate?

There’s an increasing awareness of the possibility of allergies or intolerances to feeds or feed ingredients, among horses, but how prevalent are they?

We’re all aware of the dramatic and potentially drastic reaction that the human body can have to certain foods but true feed allergies in horses are relatively rare.  Allergies involve the stimulation of the immune system to react excessively against a certain protein or protein-like molecule (allergen) which would not normally happen in the non-allergic horse.  This reaction results in the release of histamines which, when produced to excess, cause symptoms which may vary from sneezing and wheezing to itching, swelling, hives (lumps on the skin) or diarrhoea.
The symptoms of feed allergies can include swelling of the lips and mouth but are more commonly seen as diarrhoea and/or hives, although symptoms alone are not necessarily indicative of an allergic reaction to something the horse ate.  Allergies can be hard to diagnose and, in severe cases, a vet may carry out blood and skin tests with varying degrees of success. 

A more common occurrence are hyper-sensitive reactions to substances which do not involve the immune system and these tend to be referred to as intolerances.  They can result in many and varied symptoms which may not necessarily, in the first instance, be attributable to a feed-related issue and, as such, can be equally hard to diagnose.  Indeed, it is only in recent years that intolerances to feeds or feed ingredients have become recognised so, although there’s a perception that they are becoming increasingly prevalent among equines, it’s more likely that we are simply more aware of their existence.
Symptoms of a feed intolerance can include, “crabby” or “jumpy” behaviour, hives, dry itchy skin, loose droppings or a tendency to colic, all of which can also be the result of environmental and management issues.  Any horse which is uncomfortable in its gut, for example, is likely to be crabby, unsettled and prone to colic so eliminating all which could be causing this can help settle the situation.  Stress is a primary factor in gut discomfort and this can have innumerable causes from insufficient turn-out or bullying in the field to travelling, competing, over-zealous training; the list goes on.

One common consequence of a “stressed-out” equine is EGUS (Equine Gastric Ulcer Syndrome) as a result of acid attacking the lining of the horse’s stomach.  Any horse prone to ulcers or any digestive discomfort MUST have constant access to forage and the starch content of any supplementary feed should preferably be kept to a minimum.  The simple provision of ad lib forage can help reduce stress levels by satisfying a horse’s physiological need to chew and ensures there is always some food in the stomach to stop the digestive acid reaching areas it shouldn’t.
A constant flow of fibre through the digestive system also ensures that any gases which are produced during digestion are carried through thus avoiding a build-up which could cause colic.  Fibre from forage is also essential to maintain a healthy population of gut bacteria, which are also instrumental in its digestion and any imbalance can not only affect digestive efficiency but gut pH (acidity) and symptoms of an imbalance can include, loose droppings, diarrhoea or colic. 
Digestive Enhancers

Any horses with loose droppings, whether continuously or during times of stress, would benefit from a digestive enhancer like a pro or prebiotic, like Baileys Digest Plus.  Probiotics contain live bacteria and can be fed to replenish gut bacteria populations which may have been depleted, whilst prebiotics support the existing populations of beneficial bacteria and help them flourish. 
They may either act as a food source which only good bacteria can utilise or by disabling pathogenic bacteria and facilitating their removal.  In severe cases it can be worth feeding a course of a probiotic followed by a prebiotic which can then be fed daily or just during times of stress to help maintain a healthy bacterial balance, supporting gut efficiency and helping alleviate loose droppings and discomfort.

Scurfy or itchy skin can be a sign of a dietary imbalance and a look at the overall balance of the diet should always be taken before turning to supplements or special feeds in an attempt to alleviate specific symptoms.  A fully balanced diet, supplying correct levels of essential vitamins and minerals and quality protein, helps support health and well-being, of which visual signs will include, strong healthy hooves and a shiny coat.  Omega 3 oils are also essential for soft supple skin and may be found in a good quality feed or balancer or can be added to a fully balanced diet in the form of a high oil supplement or straight vegetable oil.
Elimination Diets

Feeding the recommended amount of a compound feed or balancer alongside forage will ensure the diet is supplying all the nutrients a horse needs for well-being and to support its work.  Should problems persist and remain unexplained, then a feed intolerance is possible but the only way to find out what is causing the reaction is to put the horse on an elimination diet.  Whilst this can be difficult for the hard-working horse or poorer-doer, it may be the only option and involves cutting out all supplementary feeds and giving just ad lib forage for a minimum of four weeks.
By this time, unless the cause is within the pasture or forage, symptoms should have subsided and other feed ingredients can be reintroduced one by one until a problem recurs that can be attributable to what has been added to diet.  Your vet or feed company nutritionists can help you plan the process and discuss feeds or feed ingredients which you can add separately to aid in the identification of the culprit.  It’s entirely possible that the problem is contained within the horse’s grass, hay or haylage but this should become apparent if problems persist despite the elimination of the usual suspects in compound feed.
Special Feeds
Since elimination diets can be both time consuming and complicated to exercise, there’s an increasing tendency to assume, not only that an intolerance exists but also that it is due to one or more of a number of commonly implicated ingredients.  Feeds are available which avoid these ingredients so offer a potential “quick fix” meaning that neither the specific cause nor any environmental implications are ever addressed.  Should an elimination diet result in the recognition of a reaction to a specific ingredient, then such feeds can prove useful in re-establishing a fully balanced diet whilst avoiding intolerance reactions.
Feed ingredients which have been identified as causing hyper-sensitive reactions include certain cereals, alfalfa and molasses.  If a horse is truly allergic to any of these, it is a protein which they contain that will be the actual allergen; oils, starch, cellulose or sugars are not allergens and cannot cause an allergic response. 
Bad Press

Indeed sugar often receives bad press which is unwarranted since it is both an essential nutrient and a natural component of the horse’s diet because grass has a high sugar content.  Feeds which contain molasses are often perceived to be “high sugar” but not only is molasses not 100% sugar (it’s what’s left after the sugar has been extracted, after all!) but it is used in feeds at an inclusion rate of less than 5% so the actual amount of sugar it contributes to a horse’s diet is minimal. 
So, while there’s no doubt that horse’s can be allergic or intolerant to something in their diets, there are other factors to consider when presented with potential symptoms.  Contrary to popular perception too, modern compound feeds from reputable manufacturers contain carefully prepared natural ingredients and are backed by meticulous research to ensure that they provide the very best and safest nutrition for the horse.