The art and science of feeding horses prone to gastric ulcers

Words - Sarah Nelson

Risk factors for squamous or ‘non-glandular’ ulcers are well documented and include low forage diets and long periods without eating, diets high in non-structural carbohydrate (NSC) or ‘starch and sugar’, intensive exercise and stress, as well as prolonged periods of stabling and travelling. While some risks may be unavoidable for racehorses in training, diet is one that can be influenced relatively easily. 

In this article, Nutritionist, Sarah Nelson, discusses some of the science and provides practical advice on the nutritional management of horses prone to non-glandular ulcers. While glandular ulcers may be less responsive to changes in diet, the same nutritional management is generally recommended for both glandular and non-glandular ulcers. 

Evidence that diet makes a difference

Research published by Luthersson et al (2019) was the first to show that changes in diet can reduce the recurrence of non-glandular ulcers following veterinary treatment. In this 10-week trial, fifty-eight race/ competition horses were paired according to their workload, management and gastric ulcer score (non-glandular ulcers graded 0-4). One horse from each pair continued with their normal diet while the other had their normal ‘hard feed’ replaced with the trial diet which was divided into three equal meals. Horses with grade 3 and grade 4 ulcers were also treated with the recommended dose of omeprazole for four weeks. All horses were scoped at the start of the trial, immediately after omeprazole treatment had finished and 6 weeks after treatment had stopped. 

The majority of horses improved as a result of omeprazole treatment regardless of diet. Diet had no effect on grade 2 ulcers. At the end of the study, gastric ulcer scores in the horses that were fed the trial diet were not significantly better or worse than in horses that were not fed the trial diet. Overall, gastric ulcer scores in horses that were fed the trial diet remained improved 6 weeks after treatment had stopped. Six weeks after treatment had stopped, gastric ulcers scores had worsened in the majority of horses that remained on their normal feed so that overall, there was no difference between pre and post treatment scores.  

Importantly, this research shows that changes in diet can help to reduce the risk of gastric ulcers recurring after treatment, even if other changes in management are not possible. There was also no apparent long-term benefit of omeprazole treatment alone, highlighting the importance of other strategies in the long-term management of horses prone to gastric ulcers.  As this study only evaluated changes in ‘hard feed’, it is possible that greater improvements could have been achieved if changes to forage were also made. 

Recent research reveals unexpected results

Regular turnout often isn’t possible for horses in training and while the risk of gastric ulcers generally seems lower in horses at pasture, recent research carried out in Iceland by Luthersson et al (2022) has highlighted this may not always be the case.

In Iceland, horses typically live out at pasture, often in large herds and if stabled, they are generally fed a high forage, low starch and low sugar diet. While Icelandic horses do get gastric ulcers, it’s been suggested that the over-all incidence is low. 

The aim of this study was to investigate the incidence of gastric ulcers in Icelandic horses moving from pasture into light work. Prior to the study, all horses had lived out in large herds for their entire adult lives (age range 3-7 years), had never been in work and were fed supplementary forage in winter months only. All horses were scoped within two weeks of being removed from pasture (prior to starting ‘training’) and were scoped again approximately after 8 weeks of being stabled and doing light work. Most horses were fed forage only during the training period, but 11 were given very small amounts of soaked sugar beet and 3 were given a small amount of commercially produced feed. However, in all cases, starch and sugar intake from ‘hard feed’ was equivalent to less 250g per meal for a 500kg horse which is well within the current recommendations for horses prone to gastric ulcers.

Approximately 72% of horses had non-glandular ulcers (grade 2 or above) at scope 1. The prevalence and severity of gastric ulcers improved after eight weeks of stabling and light work - approximately 25% of horses had non-glandular ulcers (grade 2 or above) at scope 2. Horses given forage three times per day as opposed to twice per day were almost 18 times more likely to improve! Over-all, the incidence of glandular ulcers decreased from 47% to approximately 41% 

The high prevalence and severity of non-glandular ulcers at the start of the study, and the subsequent improvement following the training period was unexpected. Not only is this research an important reminder that horses at pasture are still at risk of gastric ulcers, it highlights the importance of regular forage provision. 

Forage focus

Forage is critical for mental wellbeing and digestive health in all horses but sometimes receives less attention than ‘hard/ concentrate’ feed, particularly for performance horses. When it comes to reducing the risk of gastric ulcers, one of the main benefits is promoting chewing. 

Saliva provides a natural buffer to stomach acid but unlike people, horses only produce saliva when they chew, which is why long periods without eating increase stomach acidity. In one study, the risk of non-glandular ulcers was found to be approximately 4 times higher in horses left for more than 6 hours without forage, although the risk may be greater during the day. 

Research by Husted et al (2009) found gastric pH drops in the early hours of the morning, even in horses with free access to forage. Not only do horses generally stop eating/ grazing for a period of time during the early hours of the morning, they are normally less active at night, reducing the risk of gastric splashing.

It should also be remembered that forage is a source of fuel – even average hay fed at the minimum recommended amount may provide close to 45% of the published energy requirement for a horse in heavy exercise. Forage analysis can be a useful tool, especially if you can source a consistent supply. 

Routine analysis normally includes measuring / calculating the water, energy and protein content, as well as providing an indication of how digestible the fibre is - more digestible forages yield greater amounts of energy and can help to reduce the reliance on feed.

Minimum forage intake

Ideally all horses, including racehorses in training should be provided with as much forage as they will eat. However large amounts of bucket feed, intense training and stress can affect appetite so voluntary intake (how much is eaten) should be monitored wherever possible. 

In practice, this means weighing the amount of forage that’s provided, as well as any that is left in a 24-hour period.  Ideally, total daily forage intake should not be restricted to less than 1.5% bodyweight per day on a dry matter basis, although an absolute minimum of 1.25% bodyweight (dry matter) is considered acceptable for performance horses, including racehorses in heavy training. 

On an ‘as fed basis’ (the amount of forage you need to weigh out), this typically equates to (for a 500kg horse without grazing):

• 9kg of hay if it is to be fed dry or steamed (or an absolute minimum of 7.5kg)

• 11-12kg* of haylage (or an absolute minimum of 9-11kg*)

The difference in feeding rates can cause confusion but essentially, even unsoaked hay contains some water and the water doesn’t count towards the horse’s forage intake. 

*based on a dry matter of 65-70%

How much starch and sugar is ‘too much’?

The fermentation of starch by bacteria in the stomach results in the production of volatile fatty acids which in conjunction with a low pH (acidic environment), increases the risk of ulcers forming. Current advice, which is based on published research, is to restrict non-structural carbohydrate (NSC) or ‘starch and sugar’ intake from ‘bucket feed’ to less than 1g per kilogram of bodyweight per meal and ideally less than 2g per kilogram of bodyweight per day. For a 500kg horse, this is equivalent to:

• Less than 500g per meal 

• Ideally less than 1kg per day

Traditional racing feeds are based on whole cereal grains and as a result, are high in starch. By utilising oil and sources of highly digestible fibre such as sugar beet and soya hulls, feed manufacturers can reduce the reliance on cereal starch without compromising energy delivery. 

Meal size matters

There are several reasons why horses should be fed small meals but one that’s of particular importance to managing the risk of gastric ulcers is reducing the amount of starch and sugar consumed in each meal. 

Large meals may also delay gastric emptying and in turn, lead to increased fermentation of starch in the stomach, especially if cereal based. Restrict total feed intake to a maximum of 2kg per meal which is equivalent to approximately 1 Stubbs scoop of cubes.  

Feeding ‘chaff’ to prevent gastric splashing

The horse’s stomach produces acid continuously (although at variable rate). Exercise increases abdominal pressure, causing acid to ‘splash’ onto the stomach lining in the non-glandular region where it increases the risk of ulcers forming. Exercise may also increase acid production.

Feeding short chopped fibre helps to prevent ‘gastric splashing’ by forming a protective ‘fibre mat’ on top of the contents of the stomach and may be of increased benefit to horses on restricted forage diets. Current advice is to feed 2 litres of short chopped fibre volume – equivalent to 1 Stubbs scoop – within the 30 minutes prior to exercise. Ideally choose a fibre containing alfalfa as the high protein and calcium content is thought to help buffer acid.

Supplements safety & efficacy

Supplements are often an attractive option, with owners and trainers from various disciplines reporting benefits. Unfortunately, scientific evidence is currently limited with some studies producing conflicting results which means specific recommendations regarding the optimum blend of ingredients and recommended daily intakes have not been established. 

However, ‘ingredients’ that may help to support gastric health include pectin and lecithin, omega 3 fatty acids, fenugreek, threonine, liquorice and maerl, a marine derived source of bioavailable calcium. But don’t forget, there are some important safety considerations, both for horse health and mitigating the risk of prohibited substances. 

• Supplements should never be used as an alternative to veterinary treatment or an appropriate diet.

• Beware of bold claims – if it sounds too good to be true it probably is!

• It is illegal for manufacturers to claim products can cure, prevent or treat gastric ulcers. Words like ‘soothe’ and ‘improve’ are also prohibited. While bold or illegal claims do not automatically mean a supplement presents are unsafe, it does raise questions over the company’s ethics. 

• Speak to a nutrition advisor before feeding supplements containing added vitamins and minerals as some can be harmful (or even toxic) if oversupplied.

• Avoid supplements (and feeds) containing added iron.

• Be cautious of supplements containing iodine, including naturally occurring sources such as seaweed.

• Ensure the total diet provides no more than 1mg selenium per 100kg bodyweight (5mg per day for a 500kg horse).

• Natural does not always equal safe – avoid herbs of unknown origin.

• In the UK, use only BETA® NOPS (British Equestrian Trade Association, Naturally Occurring Prohibited Substances) approved feeds and supplements.

• Only use supplements produced by an authorised feed manufacturer (supplements are classified as feeds in the UK and the EU and regulated by the same legislation). Approval numbers must be included on the label but knowing what to look out for can be tricky. That said, any supplement carrying the BETA® EGUS approval mark will have been produced by an authorised manufacturer.

The BETA EGUS approval mark 

Although they are by no means the only suitable option, you can be assured that feeds carrying the BETA® EGUS approval mark have been through a rigorous independent review process to ensure:

• The combined starch and sugar content is less than 25% for high energy feeds and less than 20% for low-medium energy feeds

• They provide less than 1g of starch and sugar (combined) per kilogram bodyweight per meal when fed as recommended

• No inaccurate or medicinal claims are made on the packaging or in marketing materials

• The feed is correctly labelled

• It fulfils the nutrient specification – this includes independent laboratory analysis

Full references for scientific research available on request.

Understanding and treating depression in horses

Introduction

While depression is widely recognised in humans, it is a condition which is often overlooked in animals. The symptoms and clinical signs of depression vary from species to species but recent studies have shown that humans and horses share some characteristic warning signs which are important to recognise.  

Horses are prey animals with a well-developed fight-or-flight response and their behaviours are controlled by the nervous and endocrine system.  Like all animals, behaviour is influenced by many external factors that include genetic predisposition, environment, physiology, experience and learning. Foals are neurologically mature at birth and soon after birth can identify and react to dangerous stimuli, but like humans, the horse’s brain function does decrease with age resulting in increase in anxieties and fears. 

The brain and its neurotransmitters play an instrumental role in the temperament and behaviour of the horse; therefore, abnormal levels of various hormones can lead to a change. Normal survival instincts for the horse fall into two broad categories that includes ‘something to fear and must flee’ and ‘something not to fear and should be explored or ignored’. New research has also demonstrated that there is not a linear dominance hierarchy but rather the herd communicates with positive reinforcement and less from punishment.

In order to achieve the best results when training, it is important to consider these natural behavioural instincts. Maintaining a positive mental attitude in both training and management regimes for the horse will have considerable benefits to performance and reduce negative behaviours. 

What is depression? 

Depressive disorder (also known as depression) is a mental disorder that can occur in horses.  It involves a depressed mood or loss of pleasure or interest in activities for long periods of time.  Depression affects how the horse thinks and behaves and may lead to a variety of potential physical problems.  

While depression is widely recognised in humans, it is an illness which is often overlooked in animals.  The symptoms and clinical signs of depression vary from species to species but recent studies show that humans and horses share some characteristics. With racehorse welfare being a key topic at present, understanding and recognising small behaviour changes can allow for small management adaptations to be made thus enhancing the horses wellbeing. 

The research 

Recent research from France alongside the growing body of research, suggests that horses may develop something similar to depression in a response to physical or social discomfort.   

Researchers have observed horses that become withdrawn because of undergoing a cognitive shift.  It has been found that horses tune out to their surroundings due to physical or psychological stress.  Horses have the cognitive ability to be attentive; however, with the presence of chronic stressors there is a delay in a horse's response as they have “switched off” from their environment and demonstrated sensory inattention. 

Because we do not truly know how the horse is feeling, the hypothesis currently being considered is that the horse develops an “inward-oriented attention” when subjected to chronic disorders.  It must be stressed that this long delay in attentiveness does not indicate a state of calm for the horse but a withdrawal from its surroundings. 

Dr Georgia Mason from The Ontario Veterinary College has suggested that a horse may respond similarly to humans with depression.  It is thought that the horse’s withdrawal can be a result of a ‘learned helplessness’ in that responding to negative stimuli does not make any difference.  Thus depressed people are prone, for example, to judge ambiguous stimuli as being unlikely to be positive and to recall unpleasant memories more readily than pleasant ones.

In addition, a number of studies have assessed cortisol levels in those horses that are withdrawn. Cortisol acts to assist in relieving stress by increasing glucose metabolism to provide energy, which then enables the horse to escape from the stress. In the short-term, cortisol release is beneficial to the horse to help it cope with a stressor. This study found that abnormally low levels of cortisol (hence a physiological depression) were found in withdrawn horses that are in a pathological and depressed state.  These depressed horses also expressed anhedonia, which is the loss of pleasure to feed on an appetent substance.  

Further studies and research are needed to better understand the pathology of depression in horses.  It has been suggested that the life conditions, such as food, space, social conditions and health problems should be questioned and observed in order to identify potential acute or chronic stressors that may lead to depression. 

However, there are reviews that question the current animal models of depression and suggest that ethological models of mood disorders based on animals living under natural conditions need to be improved and developed. 

Symptoms of a depressed horse 

It is important to become acquainted with potential signs of depression in the horse so that you can identify them quickly.  By identifying the symptoms of depression, one can rapidly begin the task of identifying the underlying cause such as an injury, illness, social or environmental stressor.  With these tools, one can reduce the risk of the short-term and long-term negative effects that could ultimately hinder the horse’s health and performance.  

Lack of response

In humans and animals, being attentive is one aspect of subject cognitive abilities and capacities. The delay in responding to stimulation shows that withdrawn horses ‘switch off’ from their environment and show sensory inattention. Such lapses of attention are likely to be associated with the chronic effect of stressors, which might be expected to induce a lowered state of arousal.

A French study from the Universite de Rennes, demonstrated that depressed horses that were subjected to a series of five new, unique and unusual sounds were significantly less likely to pay attention to the noises compared to normal horses.  Their findings demonstrated that the withdrawn horses had undergone a cognitive shift that they were so physically or psychologically stressed that they developed sensory inattention. 

Heightened anxiety 

While the depressed horse will often be disinterested in everyday activities, people and companions, they are likely to demonstrate heightened emotions towards challenging situations and new stimuli as they try to express their discomfort. Stimuli that are usually unremarkable to the horse may become uncomfortable for the horse and make them “spooky”, anxious or fearful when they weren’t before. 

Lack of interest in food 

A change in mental well-being in your horse can lead to a loss of appetite.  The potential complications are the loss of weight, condition, muscle development, fitness, energy levels as well as the increased susceptibility to infection and prone to other health conditions such as colic or gastric ulcers. 

There are other illnesses and ailments that can lead to inappetence; hence, it is worth seeking veterinary advice in order to rule out any other physical problems.  

Anhedonia

Dr Carole Fureix looked at anhedonia which is the loss of feeling pleasure from experiences that used to be pleasurable.  This symptom is prominent in the depression of humans. Her study demonstrated that horses who are at times withdrawn are more anhedonic than those that are not withdrawn.  She concluded that this is a key symptom of clinical depression and suggests that withdrawn horses are indeed in a depression-like state.  

The horse may show unwillingness to work or no longer take pleasure in work they used to enjoy. This is especially important when considering rider and horse safety too as a withdrawn horse may not react appropriately to potentially dangerous situations.

Posture

Standing facing the stall wall for periods of time while demonstrating a withdrawn posture showing a fixed gaze, neck stretched out level with back, eyes open but lack of eye and ear movement. This differs from a content horse that is resting and displaying relaxed muscles, laterally rotated ears, the drooping of its eyelids and lips and holding its neck such that it slopes lower and rounder.  

Physical changes are perhaps somewhat easier to spot with a withdrawn posture being one of the typical signs of depression.  A healthy and content horse will stand with their head up and ears moving inquisitively.

Causes of depression 

The domesticated horse is often managed in such a way that they cannot express their natural behavioural instincts, thus exposing them to stressors which can lead to depression.

Lack of adequate positive social interaction with other horses 

A study from Michael Steger and Todd Kashdan explained that dysfunctional social behaviour has been implicated in the experience of depression. 

In addition, Timothy Elmer and Christoph Stadtfeld described individuals with depressive symptoms are more likely to be isolated from their social group(s), which can further increase their symptoms.  

Similarly, lack of social interaction without conscious choice for extended periods of time can lead to depression in humans.

Lack of adequate exercise and/or turnout 

It is well documented in human medicine that exercise and physical activity can improve many health conditions. Research on depression, anxiety and exercise demonstrates that the mental health and physical benefits can help improve mood and lessen anxiety.  The link between depression, anxiety and exercise are not entirely clear.  It has also been shown that exercise and physical activity may help keep depression and anxiety from coming back. 

Companionship reduces stress in the horse, hence naturally  living in a herd.  Horses are able to form companionships with their own species and other animals including humans.  In fact, horses kept in isolation, such as in closed stables, can become anxious, flighty and difficult to manage. 

Exercise releases endorphins which are feel-good chemicals in the body and also allows for more social interaction.  A recent University of London study demonstrated that people with low aerobic and muscular fitness are nearly twice as likely to experience depression.  

Illness or injury that causes pain or discomfort 

In humans studies have found that anywhere between 30-85% of patients suffering from chronic pain are also clinically depressed. Other illnesses in humans such as nutritional deficiencies, cushing’s disease, lyme disease, chronic pain, and insulin resistance can cause depression.

Stress during training, competing or in the daily routine 

If there is chronic stress in which the horse’s physiological stress response is taxed beyond what it is designed to do it can begin to impair the horse possibly leading to depression 

Inflammation and depression 

There is evidence that there is a link between inflammation and depression. Inflammations that lead to serious depression in humans can be caused by infections such as those caused by bacteria, viruses or even parasites.  There is increasing evidence that inflammation can cause depression because of the increase of cytokines setting the horse’s brain into “sick mode”.   

Treating depression

Simple changes in management can help treat the underlying cause of depression and can substantially improve the horses well-being thus having a positive impact on performance.

Light therapy

Modern management methods mean that horses can spend a large amount of time stabled which impacts the horse’s circadian rhythm (body clock). 

A study was performed at Nottingham Trent University where trial horses were put under an hour of high intensity broad spectrum light every day for six weeks. Their behaviours regarding feeding, sleep patterns and attitude to being handled and ridden were compared to a group of horses that had not received the therapy. The untreated horses were noted to be sleeping longer, lazier at ridden exercise and grumpier.

Light therapies have many positive benefits that can reduce signs of depression and improve overall well being; better daytime alertness and improved rest and sleep pattern, extending summer coat and body condition and encouraging the body to convert feed to muscle mass, noticeably fewer stable vices such as box walking, cribbing, weaving and reduced bacterial pathogens and fungal load leading to improved respiratory function.

Management

Racing is already making moves to ensure the best welfare conditions for horses, with German trainers now having to comply with regulations regarding size of stable, the amount of light in the stable, the provision of windows enabling horses to socialise and turn out capacity for a minimum two hours per day.

Increasing turnout time is reported to have positive effects on their horses' mental wellbeing, reduces stiffness and lowers the rate of stable vices. It also allows the horse to make social connections whilst allowing them to show their natural instinctual behaviours. 

With horses in varying routines in large yards, this can sometimes become stressful to some individuals. By providing company of other horses when stabled, this can help with social interactions and reduce stress. Stable enrichment and adlib forage can also replicate positive behaviours in the stable. 

It is known that exercise releases ‘feel good’ endorphins, thus, keeping the horse in a regular training regime complimented with the correct nutrition will be beneficial. 

Veterinary advice

It is important to seek veterinary advice should the horse be exhibiting signs of depression to help identify the underlying cause. Diagnostics such as blood tests can ensure there is no infection present and work-ups will highlight any pain or discomfort.

Conclusion 

While depression is widely recognised in humans, it is an illness which is often overlooked in animals. Depression in horses can be significant and harmful regardless of the underlying cause and can be temporary or long term. It is vital to ascertain the underlying cause of depression in a horse in order to treat and remedy the illness.