If you’ve ever wondered what is a low-starch diet for horses, and more importantly, should my horse be on one, then you’re not alone. However, it isn’t ideal for all horses. Ultimately, it will depend on their caloric requirements, the work they’re in and existing health conditions..
Forages should of course be the basis of any diet and are 75-90% carbohydrates. Carbohydrates include sugars, starches, and some fibre. These carbohydrates found in pasture and hay fall into two broad categories: nonstructural and structural. So horses actually rely on carbohydrates as the largest portion of their diet. Especially soluble and insoluble fibres that make up forage.
Carbs, sugars and starches in forage.
Non-structural carbohydrates (NSCs) in forages are simple sugars and fructans and can be readily digested or fermented by horses. They are produced in plants during warmer weather, and are higher in more immature forages. Pasture is usually lowest in NSCs in the early morning unless overnight temperatures are cold. However, these carbohydrates can affect some disease processes, so you need to monitor how much your horse eats.
Carbs, sugars, and starches in your horse’s hard feed
Grain based hard feeds contain carbohydrates, including simple sugars and starch. Grains such as barley, maize and oats are high in NSCs, mostly starches. Starches are long chains of attached sugar molecules. These sugars get broken apart during the digestive process and the simple sugars (glucose) readily absorbed. Most horses can digest and absorb sugars and starches in the small intestine through a process called hydrolysis. From there, glucose in the bloodstream triggers the pancreas to release insulin. Then the glucose molecules move into cells for storage as glycogen. This is the fuel for the working muscles.
If there’s more starch in a single meal than the horse can digest, starch will enter the caecum, (the first part of the hindgut after the small intestine). Any undigested starch here is rapidly fermented creating lactic acid. This lowers hindgut pH, killing the good bacteria that live there. The endotoxins released from microbial death can then contribute to both colic and laminitis.
So, just how much starch is in a low-starch diet for horses?
A “low-starch” feed usually contains less than 15% starch, but some feed companies might classify low-starch as any feed below 20%. Compare this to a traditional hard feed with grains such as barley, maize and oats as its base. These types of feed might be as much as 40-60% starch. A “mid-level” starch content is usually between 20 and 25%. Whilst many horses are fed high starch feeds seemingly without problems, the key consideration that still remains for any horse is how much starch is fed in any one meal.
Ultimately, there is no single definition of a “low- starch” diet as both sugar and starch concentrations are important. Therefore, it’s better that feeds are referred to as ‘low-sugar and starch’ or ‘low nonstructural-carbohydrates (NSC). NSC is a laboratory measure containing starch plus all water-soluble carbs (sugars and fructans). The recommendation for horses with metabolic issues therefore is not actually low-starch but low-Non-Structural Carbohydrates. So, if f low starch/low NSC is a primary concern for your horse and it’s not quoted on your bag of feed, then contact the feed manufacturer directly to find out.
Starch Content of Common Feed Ingredients
|Legume hay (besides lucerne)
|Mixed, Mostly Grass, Pasture
|Beet Pulp, Dried, No Molasses
|Maize, Whole Grain
Data collected from Equi-Analytical Laboratories
When should your horse have a low-starch diet?
For some horses with certain health conditions, vets and nutritionists might recommend a low-starch diet to help maintain blood glucose at a steady level. These are conditions that cause horses to become more sensitive to sugars and starches. This then means that owners will need to reduce these levels in both forages and concentrates. Individual horses have variable responses related to a variety of factors, including age, body condition, fitness, metabolic status, and disease status.
Obesity and equine metabolic syndrome (EMS)
These metabolic conditions are of major concern and there needs to be an overall reduction in calories consumed, not just from starches. Some breeds, especially pony breeds are “metabolically thrifty”, so they’re able to readily convert glucose into fat for storage. They will benefit from a lower-quality forage and no hard feed. This is where a quality feed balancer supplement such as one from the Fibregenix range, is ideal. It will provide vitamins, minerals, protein, fatty acids and other essential nutrients to bridge nutritional gaps in forage.
Insulin dysregulation (ID)
Insulin dysregulation is considered a component of EMS. In affected horses or ponies, insulin is not effective at transporting glucose from the bloodstream into cells, so both remain elevated. This can increase susceptibility to laminitis. Horses with this condition are extremely sensitive to starches. Ideally, they should be on as low a starch and, specifically, soluble-carbohydrate diet as possible.
Pituitary pars intermedia dysfunction (PPID, formerly Equine Cushing’s)
This endocrine disease mostly affects horses or ponies over the age of 15. Some, but not all, PPID horses will require a lower-starch diet. PPID horses that are also insulin-dysregulated are the ones which will benefit. However, some PPID horses are thin, non-insulin-dysregulated, and they need calories. In such cases a more traditional NSC level is fine.
Polysaccharide storage myopathy (PSSM)
Horses with this muscle disorder often have a normal glucose/ insulin metabolic process. They’re unable to use the form of glucose stored in their cells as energy and are also susceptible to tying-up (exertional rhabdomyolysis). This is the breakdown or destruction of skeletal muscle cells associated with exercise.
Laminitis prone horses and ponies should also have diets low in soluble carbohydrates and starch. Elevated levels of starch reaching the hindgut can lead to hindgut acidosis, killing off the good microbes. This releases endotoxins, which can negatively affect enzymes involved in maintaining the integrity of the laminae in the hoof leading to laminitis. Susceptible horses should not be allowed to graze immature or lush, rapidly growing pasture routinely found in spring and early autumn.
Gastric ulcers (EGUS)
Signs of this condition include poor performance, poor attitude, and mild colic. Horses prone to ulcers and hindgut acidosis benefit from a low-starch/high fibre diet. This is because chewing and consuming fibrous carbohydrates produces more saliva which in turn helps reduce acidity in the stomach.
Anxious or hyperactive horses may also benefit from less starch in their diets. Multiple studies (Bulmer et al., 2019; Destrez et al., 2015) have focussed on the diet’s effect on behaviour. But more recently, they’ve focussed on the “why” behind this. The latest studies have revealed that glucose is a sugar that easily crosses the blood-brain barrier. Elevated glucose levels are associated with increased dopamine production. And this can lead to elevated awareness or hyperexcitability.
Should you change your horse to a low-starch diet?
If your horse doesn’t have any of the aforementioned conditions, then he probably doesn’t need a low-starch diet. In fact, performance horses benefit from a diet with readily available carbohydrates needed to replace the stored glycogen in skeletal muscle. Especially those that do anaerobic exercise (short bursts of high-intensity training) during work. When muscle glycogen is low, the muscle adapts by slowing contraction rate and power to conserve fuel (glycogen). This is obviously not desirable in a competition horse. Traditional hard feeds with grains such as barley, maize and oats as its base might be as much as 40-60% starch. A “mid-level” starch content is usually between 20 and 25%. Whilst many horses are fed high starch feeds seemingly without problems, the key consideration that still remains for any horse is how much starch is fed in any one meal.
Similarly, hard keepers might not be good candidates for low-starch feeds either, unless you increase the fat content in the diet. These horses need more readily available calories than the fibrous ingredients often used in low- starch feeds.
The table below shows ideal targets to follow when considering how much starch your horse should have.
||% starch in your hard feed
|To avoid starch overload,rapid fermention in the h/gut
||50-65% for sweet feeds, 45-75% for straight grains
|To avoid risk of gastric ulcer syndrome
|For metabolic disorders such as IR, Cushings, laminitis etc
Making Changes To a Horse’s Diet Safely
Any changes MUST be slow and gradual so as not to upset the hindgut microflora. Gut microbes must have time to adjust to a new diet, so it’s generally accepted to make the complete transition over about two weeks.
For horses needing a low-starch concentrate, transition them the same way you would to any new diet. Start with a meal that is ¼ of the new feed and ¾ old feed and stay at this level for four days. Move up to ½ and ½ for another four days. Then switch to ¾ new feed and ¼ old feed for another four days. By the end of this period, you should be able to feed a full meal of the new feed. If you are concerned about NSC levels in forage, then limit pasture access when they’re elevated (e.g. during spring grass growth). Soak hay before feeding. Just remember to discard the soak water, so the horse doesn’t drink it.
What if a sudden change can’t be avoided?
Sometimes, the transition to a low-starch diet has to happen suddenly. For instance, after a metabolic event (e.g., laminitis) where the horse is moved from lush pasture to being yarded. Or begins to wear a grazing muzzle. In these cases, you don’t have days or weeks to make the change. So watch your horse carefully for signs of digestive disturbance such as diaorrhea. If signs develop (and if possible), back off the transition rate and make the conversion more slowly.
What if you have more than one horse and only one requires a low-starch diet? You might be tempted to think you could feed all the horses the same feed. However, whilst it may make feeding more convenient, you still have to consider each individual horse’s needs and feed accordingly.
Feeding for individual needs
What if you have more than one horse and only one requires a low-starch diet? Tempted to feed all the horses the same feed? Whilst it may make feeding more convenient, you still have to consider each individual horse’s needs.
5 Take-home messages
- A low-starch diet might be a suitable option for your horse, but it depends on his health status.
- Horses in good body condition, fit for their discipline, with high caloric demands can cope on a more traditional feed containing higher starch levels. Even so, care must still be taken with how much starch is fed in any one meal.
- Before making any changes, talk to your vet or an equine nutritionist.
- Find out how much starch is in your horse’s feed when the term “low starch” is used. This will ensure you are making decisions based on the best information available.
- Always make any changes to the diet gradually so as not to upset the digestive microbes.
A few days ago you brought your gelding in from the pasture where he’s been living 24/7. You decided to stable him during the day so you can get him prepped for an upcoming show. Today, however, he seems dull and is off his feed, with mild colic signs. The sudden change from pasture to hay and hard feed must have upset his digestive system. To avoid such scenarios it’s vital you’re aware of what constitutes good or poor horse feeding practices.
The above example demonstrates how our horse feeding practices can greatly affect our horses’ gastrointestinal (GI) health. In order to refine our management techniques, we need to first look at the diet horses evolved to eat.
Horse Feeding Practices following The Horse’s Natural Way
Horses evolved in an environment where they grazed more or less continuously—about 14 to 18 hours a day. And for good reason. Digestion in horses is less efficient than digestion in ruminants. Therefore, the horse’s feeding strategy is to eat a lot of forage to get the necessary nutrients required on a daily basis. Forage has a relatively rapid rate of passage through the digestive tract, producing lots of faeces. As long as the horse has plenty of forage, this rapid rate of passage doesn’t matter.
So this strategy works well for horses which wander, graze, and eat continually except when resting. However, a study showed that stabled horses maintained a lower (more acidic) pH in the stomach than those allowed to move around in paddocks. Movement also helps gut motility and this is why confinement is one of the risk factors for colic.
In natural settings, social contact also affects digestion. It gives horses a sense of security so they can settle down and eat. Being herd animals, the comfort of being together reduces their stress levels, promoting normal grazing behavior.
The three aspects (free movement, foraging, and social interactions) of normal equine behavior are disturbed when we confine horses in stables. By limiting free movement and feeding at set times, foraging behavior is lost. Even if they can see other horses when they stabled it’s not the same as having continual social contact. This also adds stress to their daily lives.
These changes can affect horses in several ways. Some of them adopt abnormal stereotype behaviour such as cribbing, weaving, and stable-walking. Additionally, health issues such as gastric ulcers, colic or laminitis can develop. And all these are down to the unnatural conditions, feeds and feeding practices of modern horse-keeping.
The horse’s small stomach is designed to handle continual modest amounts of high-fibre food. This is why horse feeding practices work best if the horse is trickle-feeding throughout the day and night. It can’t hold a large meal eaten all at once. Not only that, the horse’s gut also works differently from ours. Humans, like other predatory species, eat nutrient-dense meals (such as meat) and don’t have to eat again for quite a while. Horses are prey animals, eating a large proportion of fibrous material continuously to gain an equal amount of nutrients. They are constantly on the move, and on the lookout for predators.
By imposing our type of eating on the horse, thinking a horse can eat meals like us, we forget this is unnatural. It’s also detrimental to his well-being and gut health. We adopt a regime of feeding our horses just twice a day. We may even be restricting his forage, feeding in such a manner. Yet we don’t stop to think about the horse’s natural feeding behavior and how the digestive tract works.
Best Horse Feeding practices – Increase Chew Time
Foraging behavior— ie, grazing for 50 to 70% of the day—translates into heaps of time spent chewing. The horse spends a lot more time chewing forage than eating grain/hard feed. Studies have shown that for 1 kilogram of hay, a horse chews 3,400 times and takes 40 minutes to eat it. If a horse is chewing 1 kilogram of oats, he only chews 850 times and finishes it in 10 minutes.
In another study, researchers looked at how many times horses chew per day when given constant access to hay: 43,000. By contrast, a horse consuming a pelleted diet chewed only a quarter of that amount, around 10,000 times per day.
Chewing is so important because the saliva it produces helps buffer the stomach from ulcer-causing acid. Therefore, we can increase chew time by making appropriate feeding adjustments. Feeding more fibre makes our horse chew more. The solid and liquid portions readily separate with he fibre floating on top forming a mat and the liquid underneath. There are also varying particle sizes.
By contrast, if a horse consumes a 100% pelleted diet, there’s not much physically effective fibre. This leaves the particle size very small in his GI tract . The horse doesn’t have to chew pellets as he would fibre, and there’s a very uniform mix of food within the tract. That uniform mixture will increase the risk for ulcers. It won’t move through the GI tract in the same way that a non-uniform mixture would. Primarily, because there’s not enough bulk to help keep things moving along properly.
Related Content: Journey Through the Equine GI Tract
Studies were undertaken at Marion DuPont Scott Equine Medical Center, at the Virginia-Maryland Regional College of Veterinary Medicine. They studied feedstuff characteristics in the caecum of cannulated horses. (Those with surgical portals created through the abdominal wall through which researchers can access the caecum).
High-grain diets resulted in more material in the cecum that lacked good solid and fluid separation. The researchers noted that this mixture was also frothier and trapped more gas. A potential for colic.
Findings showed the caecum and colon come together at the pelvic flexure which is geared toward high-fibre forage that horses eat naturally. The more uniform mixture of modern diets might not fit as well, increasing the risk for gastrointestinal disturbances. In fact, more feed impactions occur at the pelvic flexure than anywhere else in the digestive tract.
So horses with minimal chew time are prone to not only gastric ulcers but also colic due to gas, impaction, or other issues.
Importantly, chewing also has a calming effect. Horses that chew more during the day are less likely to develop stereotypical behaviour. If they’re happily eating, they’re content, less stressed, and healthier.
Several things, however, can diminish a horse’s ability to chew. Poor tooth alignment, tooth loss, or arthritis in the jaw can all happen in older horses. He will chew less, with a higher risk for gastric problems. If the horse can’t chew fibre effectively, then you have to make dietary changes. Provide something that’s easier to chew, such as hay cubes, pellets, chaff, beet pulp, and/or a complete feed.
A Paper Trail of Feeding.
Keep precise records of what and when you feed your horse. This makes it easier to determine any causative factors if there are gastrointestinal problems.
This might include the type and amount of hard feed. Hay type and weight, feeding frequency, and diet changes.
Know the body condition of your horse and vital signs. Take these periodically so you’re familiar with his normal temperature, pulse and respiration rate when he’s healthy. It’ll help you to recognize problems early— for instance, if he goes off feed and his heart rate is increased. If any of these things are abnormal for that horse, it can be indicative of a gastrointestinal problem. You may think you know what’s going on, but a diary note is better evidence than a recollection.
Best Horse Feeding Practices – Reduce Meal Size
Remembering a horse’s small stomach size, concentrate meals should never be too large. Generally, a 500-kg horse should consume no more than 2.3 kg of concentrate feed per meal.
However, the new way of thinking for feeding horses correctly focuses more on the amount of starch in any one feed. To decrease the incidence of gastric ulcers yet still provide a high-starch meal to horses needing lots of energy, limit grams of starch per kilogram of body weight. Ie. no more than 2g of starch per kg of horse’s bodyweight. Ulcer prone horses should have no more than 1 gram of starch per kilogram of body weight in any single meal. For horses in less demanding work, some studies advocate no grain at all.
This means if your feed is 20% starch, your 500 kg horse should consume 2kg of feed per meal. If the feed is 40% starch, his meal should be half that size. This helps reduce gastric ulcer risk. Feeding more than this in one meal, increases the risk of hindgut acidosis or colic. Hindgut acidosis occurs when we overwhelm the small intestine with too much starch. It doesn’t get enzymatically digested and ends up in the hindgut. There are bacteria in the hindgut that love to digest starch and the end product of their starch digestion is lactic acid. This makes the hindgut more acidic which increases the risk for colic and indigestion.
Such horses might lose weight and develop stereotypies. Keeping a concentrate meal under 2 grams per kilogram of body weight may prevent hindgut acidosis.
Best Horse Feeding practices – Feed More Frequent Meals
Increasing the number of meals per day is a management strategy that helps reduce gastric ulcer and colic risks. However, it can be a challenging practice for people accustomed to only morning and evening feeding—before and after work.
Many horse owners put a pile of forage in front of the horse first thing in the morning or at night, thinking he’ll feed on it until the next feeding. The problem is most horses eat it all at once and by mid-morning or late evening the hay is gone.
Instead, try grouping smaller, more frequent fibre-rich meals closer together. Use a slow feeder for hay and incorporate some kind of chopped fibre (or chaff) into the grain or concentrate feeding. This will slow eating and make the horse chew more. If this is combined with some pasture access during the day, the horse will probably have less risk for gastrointestinal problems.
In fact, if you’re trying to get more calories into a horse, you’re better off feeding smaller meals more frequently. If you’re trying to feed just 1 gram of starch per kilogram of body weight, and the horse needs 5 kilograms per day (to keep weight on or provide energy for hard work), you should be feeding several meals. For example, feeding oats, which are about 40% starch, means you would feed four meals per day to keep it under 1.25 kilograms per meal. Not always a viable option of course!
Some of today’s commercial concentrate feeds can be helpful if they are high-fibre, or high in fat and fibre and relatively lower in starch and sugar. (around 20%)
Many stabled horses spend as little as 30% of their time eating. Dividing food into more meals so they can eat more often, is healthier for the GI tract than going so long between meals. Abnormal behaviors such as eating manure and bedding, or stereotypies eg chewing wood, are primarily due to the horse’s inability to graze. This means lack of chew time, insufficient fiber in the diet, and not feeling full. When a horse doens’t get his daily gut fill he’ll resort to trying to eat or chew other things.
Best Horse Feeding Practices – Make Diet Changes Slowly
As we mentioned earlier, when making any changes to your horse’s diet, do so slowly and gradually. Make any change over a couple of weeks. Eg. from hay to pasture or pellets and vice versa. From one kind of hay to another. Or in a concentrate ration, content, or quantity.
Related Content: Switching Horse Feeds Safely
Even moving from one part of the country to another, where feedstuffs might be different, can be a challenge for horses. Many people on the East Coast go from north to south every year for showing, racing, etc. When making these moves, bring a little feed (both the hay and concentrate) that the horse is accustomed to eating. Thereafter, make a gradual change after the horse arrives in his new environment.
Some horses adjust readily, others don’t, so always err on the side of caution when it comes to feeding practices. Horses are a lot like humans in that there are variations in how different horses handle change or different foods. This is down to a combination of genetic factors, microbes in the gut and differences in ability to handle different foods.
For optimum gut health, our horse feeding practices should mimic nature as much as possible. Unnatural conditions can adversely impact horses’ GI tract health and function. This means paying attention to what we feed (nutrient and fibre levels). Plus, how we feed in terms of meal size and frequency. We should always be mindful of trying to find ways to increase his eating and chew time.
If you’re unsure about your horse’s diet please feel free to contact us. Alternatively, try our free diet audit. Our Equine Nutrition consultant will thoroughly review your horse’s diet with the experience gained from over 30 years of practical, hands-on and common sense knowledge.