Straw or chaff is a high-fibre low-sugar forage that is ideal for horses that are overweight or insulin-resistant. Straw adds bulk to your horse’s diet without contributing significant calories or protein.

Research shows that adding straw to a forage ration can increase time spent grazing and the expression of natural foraging behaviours. [1] This can improve wellness and prevent boredom without adding excess energy to the diet. [2][3]

While straw is not widely used as horse feed in North America, chaff or chopped straw is commonly fed in the United Kingdom. Mixing straw with other forages is recommended to avoid health concerns that are associated with feeding a straw-only ration.

Although there are many benefits of feeding straw to horses, there are also some risks. Horses fed straw are more likely to experience impaction colic. This forage should also not be fed to horses requiring a low-dust diet or horses with dental issues.

Straw in Your Horse’s Diet

Straw is a crop residue or byproduct of cereal plants (such as wheat, oats, barley or rye) that is typically used as bedding or feed for farm animals.

It consists of the dried leaves and stems of cereal crops that remain after the grain is harvested. [4]

Straw is a coarse forage with high fibre content but low nutritional value, including low levels of digestible energy, protein, sugar, and certain vitamins and minerals. [2][5]

Because it is a low-calorie forage, it is ideal for easy keepers, horses that need to lose weight, and horses with Equine Metabolic Syndrome.

Straw can be used to add more roughage to the diets of horses expressing stereotypic behaviours, which are linked to a lack of continuous access to forage. [6]

Due to its low nutrient concentration, straw should not be fed as the sole ration for horses. Instead, it should be mixed with hay or other feeds and supplements to ensure the horse’s protein, mineral and vitamin requirements are met.

Equine nutritionists typically recommend replacing 10 – 25% of your horse’s hay with straw to support weight loss, and some researchers suggest that forage rations should not contain more than 30% straw. [7]

However, studies have looked at replacing 50% of daily forage with straw and found no ill effects. [8]

Straw vs. Hay

What is the main difference between feeding your horse straw and hay?

Hay consists of cut and dried leaves and stems from grasses and legumes that are typically harvested before the plants have matured and made seeds. In contrast, straw is the dried stalks of cereal grains harvested after the seed heads have been harvested.

Straw contains higher indigestible lignin than hay, is coarser, and tends to be less palatable. If straw is not chewed thoroughly, it could potentially irritate the stomach lining. [9]

Straw also has a different nutritional profile than hay, with generally higher fibre content, and lower crude protein, sugar, vitamin, mineral and fatty acid content.

In particular, mid-quality wheat straw provides approximately 20% less digestible energy than a comparable mixed alfalfa/grass hay. This makes it attractive for horses with lower energy requirements.

Nutritional Profile

The following table shows the nutrient composition of an average quality wheat straw compared to a mixed legume/grass hay.

Note that nutrient levels in straw and hay can vary depending on plant type, stage of maturity, growing, harvesting and storage conditions and other factors.

The best way to determine the nutritional profile of your horse’s forage is to submit a sample for analysis.

Nutrient Straw Hay
Energy 1.6 Mcal/kg 2 Mcal/kg
Fibre (NDF) 79% 57%
Fibre (ADF) 57% 38%
Sugar (ESC) 2% 8.1%
Protein 4.8% 10%
Fat 1.6% 2.8%

The Importance of Forage

The horse is a trickle-feeding herbivore that is adapted to consuming large volumes of low-calorie fibrous roughage.

The equine digestive system is optimized for continuous intake of forage, with wild horses spending between 10-15 hours grazing each day. [7]

To promote equine welfare and the expression of natural behaviours, horses should have constant access to forage and consume 1.5 – 2.5% of their bodyweight in forage daily.

For a typical 500 kg (1100 lb) horse, this is roughly equal to 10 kg (22 lb) of forage per day on a dry matter basis.

Restricting your horse’s access to forage by feeding less than this amount or going long periods without forage is associated with several hegative outcomes including: [10][11][12]

For this reason, forage restriction is not recommended as the primary weight-loss strategy for horses.

Forage Selection

Consider your horse’s energy and nutrition requirements when selecting a forage, including their age, exercise level, health and reproductive status.

Match forage quality to your horse’s energy requirements so you can provide constant free-choice access to forage.

Horses with high energy requirements due to work level or breeding status benefit from energy-dense forages, such as a high-quality grass/alfalfa mix.

Horses that are obese or overweight, have metabolic dysfunction or have a history of laminitis benefit from a low-energy diet with lower calorie forages, such as mature grass hay and straw.

Benefit of Feeding Straw to Horses

Straw is beneficial for horses that need more roughage in their diet to extend feeding time and prevent stereotypic behaviours.

It is also recommended for horses that require lower-quality forages to reduce the energy density of the diet or to create a calorie deficit for weight loss.

Lastly, straw is a low-NSC (non-structural carbohydrate) forage that may support metabolic regulation and healthy insulin levels. [2]

Extending Feeding Time

Horses consume straw at a slower rate and spend more time grazing when their forage ration contains straw. [7][8]

This is likely due to the lower palatability and high fibre content of this forage. Horses tend to eat palatable feeds quickly, altering the natural time budget for foraging behaviours. [3]

Wheat straw also contains 20% less digestible energy than typical hay, meaning a higher volume can be fed to provide the same caloric energy.

Therefore, adding straw to the diet can extend time spent grazing and allow for natural foraging patterns. [8]

Stereotypical Behaviours

Foraging opportunities for domesticated animals are often restricted by management practices, altering the horse’s natural time budget.

Horses kept in small enclosures and given limited access to forage are at risk of stereotypical behaviours and aggression. [3][8]

Diets providing less than 6.8 kg (15 lb) of forage per day are linked to behaviours such as weaving and wood-chewing. [13]

Keeping a horse on straw bedding has been shown to improve some behavioural problems by reducing boredom and frustration, and by providing natural enrichment through foraging behaviour. [14]

Weight Loss

To promote equine welfare, horses should be fed a minimum of 15 grams of forage per 1 kg (2.2 lb) of body weight or 7.5 kg / 16.5 lb for a 500 kg / 1100 lb horse. However, some horses may get too much energy from their forage even at this rate.

Feeding a diet that exceeds your horse’s energy requirements can lead to weight gain and obesity. Overweight horses have a higher risk of health conditions such as laminitis and equine metabolic syndrome (EMS).

Because straw has a lower energy density than hay, replacing some of your horse’s forage ration with straw can reduce their calorie intake, helping to maintain a healthy body condition. [2]

In one study, 40 horses were fed either a 50:50 combination of barley straw and hay or hay alone over winter. [15]

All 25 of the horses fed straw lost weight, with an average weight loss of 27 kg (60 lb). In comparison, only 3 of the 15 horses fed hay lost weight with the average horse gaining 6 kg (13 lb) over the trial. [15]

Reduced Blood Insulin Levels

Feeding straw may support metabolic health and normal blood insulin levels. Insulin dysregulation is a risk factor for laminitis and obesity. [8]

In one study, feeding a 50/50 diet of wheat straw and hay resulted in lower blood insulin levels compared to feeding grass haylage alone. [8]

This may be attributed to the generally lower ethanol-soluble carbohydrate (ESC) content of straw compared to hay. ESC consists of simple sugars – such as glucose, and starch. Glucose triggers insulin secretion when absorbed from the gut.

Considerations when Feeding Straw

Although straw benefits some horses, it may carry a higher risk of certain gut issues and may not be appropriate for all horses.

There are also different types of straw, which vary in colour, texture, length and nutritional profile. Lastly, they are some key considerations to factor in when feeding straw to any horse.

Work with an equine nutritionist to design an appropriate feeding program for your horse and to decide which type of straw and how much to feed. Ideally, submit a forage sample for analysis to balance your horse’s diet.

Digestibility

Horses are hindgut fermenters and are adapted to digest fibrous feeds with the help of microorganisms that live in the gastrointestinal tract.

In the hindgut, these microbes break down fibre and cellulose in forage through fermentation. [7] This process converts plant materials into energy and nutrients. [16]

Straw has little nutritional value and very low digestibility, which horses may compensate for by consuming more of it. [16]

Digestibility measures how much of a given nutrient is absorbed and used by the horse’s body. Because straw has high fibre content, it has low digestibility and moves through the gastrointestinal tract faster than lower-fibre feeds. [16]

Impaction Colic

Horses consuming coarse, low-quality forages are believed to have a higher risk of impaction colic. This condition occurs when a mass of food or other material gets stuck in the horse’s digestive tract, causing a blockage.

Forages with high ADF content such as mature warm-season grasses have been linked to higher incidence of impaction colic. Straw also has a high ADF content of approximately 57% which impacts digestibility. [17][18]

The sudden introduction of high-fibre feeds can lead to obstruction in the bowel. Large, dry and firm masses of forage can become stuck in the stomach or intestine, needing medical intervention to resolve.

To reduce the risk of impaction colic, straw should be gradually introduced to your horse’s diet over the span of 2-3 weeks. [7][19]

Horses must have constant access to fresh, clean water when eating straw to facilitate gut motility (the movement of feed through the gastrointestinal tract).

Ensuring adequate sodium intake also promotes water intake to support gut motility. Simply adding 1 – 2 tablespoons of salt to your horse’s diet is usually sufficient to meet their sodium requirement.

Choke

Choke occurs in horses when the esophagus becomes partially or fully obstructed due to food or another object. Horses can breathe when they experience choke, but this condition is still a veterinary emergency because complications can occur.

Choke may be caused by feed or forage that is inadequately chewed or not sufficiently hydrated with saliva. Diets containing large amounts of coarse straw may be a risk factor for choke.

To reduce the risk of choke, feed chopped straw and encourage your horse to drink lots of water. You can promote water intake by feeding your horse plain, loose salt or electrolytes.

Dental Care

Before feeding straw as forage, ensure that your horse’s teeth are in good shape with a dental examination.

Horses with bad teeth or dental issues are more at risk of impaction colic and choke because their teeth cannot grind long fibres into tiny pieces.

Avoid feeding coarse materials such as straw to horses with dental problems and older horses. Instead, feed softer forages such as soaked hay or haylage and provide feeds in a mash. [7][19]

Gastric Ulcers

Field studies suggest a higher risk of gastric ulcers in horses fed straw as the only forage. [9]

53 – 93% of domestic horses are believed to have gastric ulcers. These painful sores in the horse’s stomach can be caused by diet, restricted feed intake, stress, exercise and certain medications. [9][20]

Researchers suggest that feeding coarse straw alone may contribute to stomach ulceration due to mechanical damage to the stomach lining. Straw also has lower calcium and protein content than hay, which could reduce the forage’s natural buffering capacity of gastric acid. [9]

However, multiple studies show that rates of gastric ulcers are not increased and may actually decrease when feeding a 50/50 diet of straw and hay. [8][15]

Weanlings and Yearlings

Young horses (weanlings and yearlings) should not be fed straw as their digestive systems are not well-adapted to coarse forages. [19]

Without adult teeth, young horses cannot chew and break down coarse straw like a mature horse can. Straw also lacks important nutrients, vitamins and minerals that growing horses need for healthy development.

Yearlings should be offered high-quality hay and a vitamin and mineral supplement that meets their specific needs.

Mold and Mycotoxins (Fungal Toxins)

Mycotoxins are naturally occurring toxic substances produced by molds and fungi in hay and straw. Mold growth is common under humid, damp and warm conditions. [21]

Mycotoxins can accumulate in cereal crops during harvest and storage, jeopardizing feed safety for horses [22]. Improper storage conditions are a major risk factor for mycotoxins.

Myxotocin intoxication in horses can cause loss of appetite, diarrhea, low energy and difficulty breathing.

Moldy straw should never be used as bedding or forage. Some laboratories offer forage testing to identify the presence of mycotoxins and mold.

Straw is known to vary in hygienic quality. Always examine your forage before feeding and if you suspect your horse ingested mouldy forage, monitor their behaviour for symptoms.

Equine Asthma

Equine asthma is an umbrella term used to describe non-infectious chronic respiratory disease in horses. It encompasses conditions formerly known as Equine COPD, Recurrent Airway Obstruction (heaves), and Inflammatory Airway Disease.

Asthma in horses can contribute to exercise intolerance, poor performance and respiratory distress. It requires life-long management changes and treatment to alleviate symptoms.

Clinical signs of severe equine asthma include cough, nasal discharge, increased respiratory effort, head and neck extension and nasal flaring. [23]

Due to high dust content, straw is not recommended as bedding or feed for affected horses. Ingestion or inhalation of airborne dust in straw is a common trigger for this disease. [7]

How to Feed Straw to your Horse

Consult with an equine nutritionist to formulate a balanced feeding program for your horse that includes straw. Protein, vitamin and mineral deficiencies are a risk when feeding low-quality forages.

Nutritionists generally recommend replacing 10 – 25% of your horse’s hay with straw. Introduce this forage gradually, increasing the feeding rate by 10% every few days to the desired amount.

Ensure that the straw you feed your horse is hygienic by regularly inspecting bales. [7] If the straw seems damp, smells moldy or contains visible mold, it may be unstable for your horse.

Straw crops used as forage for horses should be cut and preserved during dry weather and low humidity to avoid mold growth. Consider purchasing bagged, dust-free straw from a feed store to use as forage.

Straw containing residual seedheads will also have higher levels of starch and sugar and may not be appropriate for horses with metabolic syndrome.

Feed a complete vitamin and mineral supplement along with your horse’s forage ration to avoid common nutrient deficiencies in your horse’s diet.

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Using Straw as Bedding

Is straw a good bedding material for horses? Bedding materials should be relatively hygienic, easy to manage and economical without negatively impacting indoor air quality. [24]

Straw is a low-cost, readily available bedding material that may benefit equine welfare. [1] Providing a horse with edible bedding such as straw allows for continuous foraging opportunities and can reduce aggressive behaviour in horses. [1][3]

Wheat straw is the most common type of straw used in animal bedding. It is soft and absorbent, making it ideal for horses housed indoors or outdoors. Oat and barley straw are more absorbent than wheat straw but not as soft, so they may not be as comfortable for horses.

However, straw contains higher levels of respirable dust particles compared to other bedding materials and may not be appropriate for horses with respiratory issues.

Straw bedding materials can produce high levels of ammonia emissions and contain mold, toxins, fungal spores, and other allergens and irritants that can affect the horse’s airways.

If your horse is susceptible to asthma or allergies, choose alternative dust-free and absorbent bedding for their stall.

Conclusion

Horses are naturally adapted to consuming low-quality fibrous forages consistently throughout the day.

Straw is a readily available and inexpensive forage with low nutritional value, making it ideal for horses on an energy-restricted diet.

Replacing up to 1/4th of your horse’s hay with dust-free straw can promote weight loss, improve insulin regulation, extend feeding time and reduce stereotypic behaviours.

Always choose hygienic straw, ensure your horse’s teeth are checked regularly, and provide fresh, clean water and free-choice loose salt to keep your horse healthy when feeding straw.

Some gastrointestinal issues are believed to occur more frequently in horses fed straw, including hay belly, diarrhea and free fecal water syndrome. While there is no research to evaluate this claim, you can support your horse’s gut health by making feed changes gradually.

Work with an equine nutritionist to formulate a balanced feeding program for your horse and determine whether straw is an appropriate forage for your horse. You can submit your horse’s information online for a free diet evaluation by our qualified equine nutritionists.

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References

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  3. Kelemen, Z. et al. Equine Activity Time Budgets: The Effect of Housing and Management Conditions on Geriatric Horses and Horses with Chronic Orthopaedic Disease. Animals. 2021.
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  11. Earl, L.R., Thompson, D.L., Jr., Mitcham, P.B. Factors affecting the glucose response to insulin injection in Mares: Epinephrine, short- and long-term prior to feed intake, cinnamon extract, and omega-3 fatty acid supplementation. Journal of Equine Veterinary Science. 2012.
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