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]

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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.