In the UK, straw is rarely used as the sole forage for horses in contrast to what is done in other countries. Some people are wary of feeding straw due to concerns that it may contribute to digestive issues in horses such as colic and gastric ulcers. Clearly, if a horse or pony gorges on straw and consumes a lot then there is an increased risk of colic but if introduced slowly and mixed with other forages, this risk is minimised. Straw lacks certain nutrients such as protein and calcium which are thought to help buffer acidity within the digestive tract and may present an issue for gastric health if fed as the sole or majority forage. However, recent studies have shown that there is no increased risk of gastric ulcers in horses when straw makes up 50% of their ration. In fact, straw can be a very useful ingredient when mixed with more nutritious fibre sources, such as alfalfa and grass, to dilute the calorie level and to maximise chew time for good doers.
Although straw is high in fibre, it has a very low-calorie content compared to other forages as it contains higher proportions of indigestible materials such as lignin. Straw is indigestible because, as the plant grows tall, it needs to develop a structure to remain upright. That indigestible material means the horse doesn’t have time to extract significant energy from the straw before it has passed through the gut.
Although straw is not always the most palatable source of fibre, most horses will eat it, especially if they are on a restricted diet and it is mixed with other forages. If your horse is on a restricted ration and you use straw as a bedding in their stable, they are very likely to browse on it which is another way horses consume straw. At Dengie, we add herbs or coatings to improve palatability, and the straw is also dust-extracted.
In the UK, and particularly here at Dengie, oat straw is the preferred choice. However, wheat and barley straw can be fed to horses too. A recent study by Jansson et al. (2021) used 50% wheat straw to replace haylage with no ill effects, and other studies have used barley straw. The nutritional value of different straws will vary to a small degree depending on the type, as well as growing and environmental conditions. On average, straw contains around 2.5% starch and 6.5% WSC (water soluble carbohydrates) (Equine Applied and Clinical Nutrition, 2013).
Straw is high in fibre and has a very low-calorie level compared to other forages. This makes straw an ideal fibre source for mixing with high quality hay or haylage to dilute the calories for good doers, especially in situations where it is difficult to buy separate forages, such as on a livery yard where forage is provided as part of the livery package.
It is recommended that horses and ponies with insulin dysregulation should be fed forages lower than 10% non-structural carbohydrate (NSC). In practice this can be very hard to achieve, especially in years when there is a long hot summer as has been seen in 2018 and 2022. NSC values in hay made in these years has exceeded 20% regularly and more than 30% in some cases. Straw provides us with a useful tool to ensure that horses and ponies that need a low NSC forage can still receive plenty of fibre to promote digestive health and satisfy their need to chew.
Another benefit of horses eating straw is that it can be included in the bucket feed. At Dengie, we use straw as a key ingredient in our Hi-Fi range to provide a lower calorie ration, helping to promote weight loss and reduce the risk of issues such as laminitis. Studies have shown that chopped straw takes twice as long to chew as other chopped fibres. Although straw has very little buffering capability on its own, it still benefits gastric health by increasing chew time, which leads to greater saliva production. This is important because saliva contains bicarbonate, which helps buffer acidity in the horse’s digestive tract.
Straw can also be made into pellets to provide low calorie fibre that can be added to compound feeds and fibre blends. Very high fibre pellets can absorb a lot of moisture which could increase the risk of choke and colic and so to mitigate this, straw is treated before it is pelleted. This process effectively starts the digestion of the straw before it reaches the digestive tract. It is widely used in human food preparation too, including to soften olives and create pretzels. Treated straw may be found on ingredients lists as NIS (nutritionally improved straw) or PTS (partially treated straw). It is important to note that a lot of misinformation abounds about treated straw. The agent used to break down the structure has to be a strong natural chemical as fibre is very complex and therefore has a robust structure. The chemical reaction that occurs actually means there is a low level of bicarbonate left in the straw. Bicarbonate acts as a natural buffer to acidity in the gut and so would be considered beneficial although because the levels are so low in NIS or PTS, it is unlikely to have any discernible effect in the horse.
Additional concerns may relate to risk of impactions which largely stem from studies published in the 1980s. In more recent studies exploring different types of bedding for horses and their implications for welfare, it is apparent that if horses have access to straw bedding they do move between their hay and their bedding and so the time taken to consume their forage ration is longer. Researchers in these welfare focussed studies advocate this behaviour and highlight that those bedded on shavings do, in some cases, eat their shavings but also spend less time eating which has negative consequences for digestive health. What we want to avoid is a horse or pony eating a large amount of straw in one go and so if it’s part of a mix of forages, this is less likely to occur. If a horse or pony has poor teeth or a history of impaction colic then straw is probably best avoided if fed in long length. It may still be suitable if chopped and mixed with other ingredients in the bucket feed though. If you are in any doubt please consult your vet.
If your horse has poor dentition or a history of impaction colic then straw may not be suitable but it is worth discussing with your vet as straw isn’t necessarily any more fibrous than some late cut hays. Chopped straw may be a viable option in these scenarios or dampening to soften may help too. As with any new feed introduce small amounts and increase gradually over at least 7 days. Mixing straw with the other forage will help to reduce the amount the horse is consuming at one time – problems typically occur when a horse gorges on one ingredient so the key is to limit the amount they can consume. Horses will often pick through the mix of straw and other forage which is great as it slows their intake even further!
Some horses won’t eat straw, even if there is nothing else on offer. Whilst it might seem wasteful, mixing straw in with other forages can mean it still serves a purpose by slowing the horse down when eating as they sort the straw out from the other forage.
Calculations using typical values for forages show that if straw replaces one third of the weight of an average hay, a reduction in energy intake of 16% is achieved. Obviously replacing half of a higher quality forage such as haylage will achieve an even greater reduction. Interestingly, research suggests that to lose 0.5 unit on a 5 point body condition scoring system is thought to require a reduction in energy intake of 11-15% in the total diet. This makes straw the ideal choice for maintaining forage intake but reducing weight.
Straw has a much lower water-soluble carbohydrate (WSC) content than grass forages so it has less of an impact on blood glucose and insulin levels when eaten. This, combined with a slow rate of consumption meant that in one study, no significant increase in insulin levels occurred in horses consuming 50% straw and 50% haylage. This is really valuable information for managing insulin dysregulated (ID) horses such as those with EMS or PPID.
The hygienic quality of straw can vary, so some care is required when sourcing some for your horse or pony. Straw can be soaked or steamed but if this isn’t practical then chopped straw is available to buy in branded packaging. This will have been dust-extracted and sourced from reliable growers.