What are the advantages of steaming or soaking hay before you feed it to your horse? There are pros and cons for each method of preparing hay.
Both steaming and soaking are beneficial for reducing dust in hay. This can have benefits for horses with respiratory conditions, such as heaves or inflammatory airway disease.
Soaking hay is superior for reducing sugar content and is better for horses with metabolic concerns or horses prone to laminitis. However, soaking can reduce the mineral content of hay and increases the risk of mould growth.
Steaming is more effective for eliminating a wide range of contaminants and airborne particles while preserving nutrients. Steaming requires specialized equipment and is therefore more expensive than soaking.
In this article, we will compare steaming and soaking hay and discuss some of the reasons to consider We will also describe the best way to steam or soak your horse’s hay.
Why Steam or Soak your Horse’s Hay
Steaming and soaking hay are management practices that can support equine health. While not necessary for all horses, these methods can benefit horses with:
- Poor dental condition
- Digestive issues such as diarrhea
- Poor respiratory health
- Metabolic concerns such as obesity or equine metabolic syndrome
Fresh grass typically contains 80% water compared to hay which contains only 10 – 20% water. Steaming and soaking add moisture to hay which makes it easier to chew and supports hydration.
Hay that is higher in water content is also easier to digest and is less likely to cause choke or intestinal impaction.
But is it better to steam your horse’s hay or to soak it? These feeding practices affect forage in different ways and the right strategy will depend on the specific health needs of your horse.
Soaking involves submerging forage in water for between 30 minutes to several hours. The most common reason to soak hay is to reduce the amount of non-structural carbohydrates (NSC) present in the forage.
This method is superior to steaming when it comes to decreasing sugar content. If your horse needs to lose weight or is insulin resistant, soaking can significantly decrease the energy density of your forage to make it more suitable for your horse.
When soaking hay, it is common to fill a hay net and submerge it in a garbage bin or plastic tote containing clean water.
Nutritionists typically recommend soaking for 30 minutes in warm/hot water or 60 minutes in cold water.
After submerging the hay, hang the hay net for at least 30 minutes to allow the water to drain before offering it to your horse.
Soaking for longer can further reduce the sugar content of the hay, but also increases the risk of mould growth and can affect palatability.
Reducing NSC Content
NSC in hay refers to the carbohydrates that are found within the plant cell and not the cell wall. A hay analysis can tell you the NSC value of your horse’s hay.
Non-structural carbohydrates in forage consist of:
- Starch: polysaccharides or long-chain polymers of glucose molecules
- Ethanol-soluble carbohydrates (ESC): simple sugars such as fructose and glucose
- Water-soluble carbohydrates (WSC): primarily fructans and pectins
The names “water-soluble” and “ethanol-soluble” refer to how the fibre content of hay is processed in the lab to measure these fractions. Soaking hay with water does not only remove the WSC; it also reduces ESC and starch content. 
Non-structural carbohydrates, particularly starch and ESC fractions, are broken down by enzymes in the digestive tract and absorbed in the horse’s foregut. They can quickly increase blood sugar levels and raise insulin levels.
In contrast, fibre is a structural carbohydrate found in the cell wall. It cannot be broken down by the horse’s enzymes.
Fibre is instead digested by microbes in the horse’s hindgut and is converted into volatile fatty acids (VFAs), which the horse can use for energy.
Horses with metabolic conditions typically benefit from restricted carbohydrate consumption and soaked hay.  Some examples of these conditions include:
- Insulin resistance
- Polysaccharide Storage Myopathy (PSSM)
- Hyperkalemic Periodic Paralysis (HYPP)
Lowering the NSC content of hay by soaking is also beneficial for horses that are overweight and on calorie-restricted diets.
Soaking decreases the amount of digestible energy in a forage. Because the hay is less energy-dense, it may be possible to feed more of it.
This can eliminate the need to restrict your horse’s forage intake and allow you to extend feeding time. Providing adequate forage can help to both prevent ulcers and avoid the development of stereotypic behaviours.
Effects of Soaking Hay
Several factors affect the reduction in NSC by soaking. These include:
- Water temperature
- Duration of soaking
- Type and maturity of forage
Research shows that carbohydrate reductions in hay due to soaking are highly variable. In one study, hay was soaked at 8oC (46oF) for 16 hours. 
The researchers looked at the WSC content of the hay before and after soaking. Prior to soaking, WSC content ranged from 123 to 230 g/kg dry matter.
After soaking, the hay lost an average of 27% of WSC content.  However, total reductions in the hay tested ranged from 6 to 54 percent of WSC. 
The average percentage losses of different carbohydrates in the hay were: 
- Fructan – 24 percent
- Fructose – 41 percent
- Sucrose – 45 percent
- Glucose – 56 percent
Different Durations & Temperatures
Length of soaking time also influences the extent of WSC reduction. One study determined that soaking hay in cold water for 20 minutes removed approximately 5% of the WSC content, whereas soaking for 16 hours removed 27%.  However, in another study, soaking for longer than 15 minutes did not further decrease WSC content. 
Given the potential for mold growth and palatability issues, it would not be recommended to soak hay for 16 hours.
Water temperature can also affect the results. Both warm and cold water can be used to reduce WSC content, but warm water requires less soaking time to achieve the same rate of carbohydrate removal. 
Reducing Respirable Particles
Soaking hay also reduces amounts of potentially respirable particulate matter (particles that can be breathed in), including dust, bacteria, mold, fungal spores, and insect fragments.
If inhaled, these particles can contribute to allergies and inflammatory airway disease by promoting hypersensitivity in the respiratory tract.
Research shows that soaking hay for 30 minutes reduces the number of respirable particles by approximately 90%. 
Soaking hay dampens these particles to reduce the amount breathed in by your horse, but does not destroy them in the same manner that steaming does.
Disadvantages of Soaking Hay
While soaking hay can have benefits for horses with metabolic concerns or respiratory issues, there are some important points to keep in mind.
Soaking hay before feeding it does not guarantee that your forage will be suitable for horses that need to avoid high levels of non-structural carbohydrates.
Horses that are obese, insulin resistant, or prone to laminitis should select hay with less than 10% NSC content. This also applies to horses with PSSM who require low sugar diets. 
The only reliable way to determine if the NSC level of forage has been adequately reduced by soaking is to have it analyzed. Even with soaking, some hays that have a high NSC value to begin with may not be suitable for these horses with special needs.
Soaking hay reduces levels of several other important nutrients including the macrominerals potassium, calcium, phosphorus, and magnesium. 
Soaking also reduces the digestible fiber and soluble protein content of the hay. 
To avoid excessive nutrient loss, hay should only be soaked for 30 – 60 minutes unless under the guidance of a nutritionist.
You should always feed a vitamin and mineral supplement or a ration balancer to ensure your horse receives adequate nutrients in their diet.
Soaking hay can actually increase levels of bacteria present and is less hygienic than steaming. Always use clean water and containers to soak your horse’s hay and feed it soon after removing the hay from water.
In a study of five types of hay, researchers found that bacterial contamination increased by 50% in hay soaked for 10 minutes and 500% if soaked for 9 hours. 
Soaking hay requires large amounts of water to completely submerse your horse’s forage. The excess water drained from hay is contaminated and must be disposed of properly to avoid polluting grazing areas or water sources.
It takes time and effort to soak hay properly. Moving soaked hay from one place to another can be messy and difficult. Wet hay is also heavier to transport around your barn.
Lastly, soaking hay adds to the cost of your feeding program by increasing your water bill. You may need to invest in equipment up front to make it easier soak your hay and to handle the large volumes of water needed for soaking. However, the upfront investment is typically less than with steaming hay.
If you have a horse with metabolic issues or respiratory concerns, one of our nutritionists can help you determine whether it is worth it to soak your horse’s hay or whether you should make other changes to their feeding program instead.
Submit your horse’s information online for a complementary diet analysis from our trained nutritionists.
Steaming Hay for your Horse
All types of hay, including those of the highest quality, can contain unwanted organisms or allergens that could negatively impact your horse’s health.
Some examples of allergens and pathogens that may be found in hay include:
- Dust Spores
- Mycotoxins produced by mold
- Plant or insect fragments
Steaming hay reduces the health risks associated with these organisms by effectively destroying most of them. An estimated 60 – 99% of bacteria is eliminated from hay by steaming. 
Steaming is more effective than soaking at eliminating these types of contaminants. Soaking only dampens particles to reduce the risk of inhalation.
Bacteria that remain after steaming include spore-forming microbes – such as Saccharopolyspora rectivirgula and Thermoactinomyces vulgaris – that can withstand high temperatures and are unlikely to be killed by steaming. 
Horses with respiratory problems, including recurrent airway obstruction (RAO), derive greater benefits from hay that is steamed than soaked.
Research shows that steaming significantly reduces mold and yeast concentrations, making hay more hygienic. 
Reduced Skin Allergies
Forages can house large numbers of bacterial contaminants and lead to allergic responses in horses. Ingesting gram-negative bacteria present in forage can elicit a strong immune response in your horse. 
Steaming may help to reduce the development of allergic skin conditions by improving the hygienic quality of hay.
Hay that contains microbial contaminants is more likely to cause digestive problems by disrupting the balance of microbes in the hindgut. This can lead to dysbiosis and related conditions, including colic.
Steaming may reduce the risk of gut issues by eliminating pathogenic microbes.
Research shows that steamed hay is more palatable than soaked hay. Steaming the hay does not appear to affect palatability when compared to dry hay. 
Whereas soaking hay can result in nutrient loss, steaming preserves most of the minerals, trace elements, and crude protein in forage.
In a research study involving 30 different hay samples, protein and mineral levels remained unaltered after the hay was steamed. 
In another study, a 16% decrease in phosphorus levels was observed post-steaming, but this was less than the 25-65% loss seen with soaking. 
How to Steam your Horse’s Hay
Steaming involves placing hay in a specially designed chamber and passing steam through it. Hay is steamed for approximately one hour and the temperature should reach above 80°C (176°F) for a minimum of ten minutes before the hay is removed.
Commercially available steamers are convenient to use, safe and effective. Hay steaming equipment is available from companies such as Haygain and EquiSteam.
Homemade hay steaming units can be constructed from materials including large bins and wallpaper steamers. Although this equipment may be more affordable than commercial devices, it may not be as effective or safe.
These devices may not produce enough steam to fully penetrate hay or be insulated sufficiently to reach temperatures high enough to eliminate bacteria.
Disadvantages of Steaming Hay
Steaming is less effective at reducing the sugar and starch content of hay. Steaming has been shown to reduce water-soluble carbohydrate levels in hay by 0 – 18%, compared to 8 – 50% for soaking. 
For horses that require low NSC hay, soaking before steaming can help. Soaking hay for nine hours followed by steaming for 50 minutes can reduce carbohydrate content while also eliminating microbial contaminants.  However, potential palatability issues are likely with this approach.
The costs of hay steaming equipment can range from several hundred to thousands of dollars.
Operating this equipment will also add to your electricity bill. Steaming devices require approximately 1.5 kWh per 60 min cycle to operate.
Steaming or soaking your horse’s forage can help to make the hay you have available better suited to your horse’s individual needs.
Soaking is the most effective method for reducing the sugar and starch content of energy-dense forages. This is the best option for obese or metabolic horses that need to avoid hays with an NSC value over 10%.
However, soaking can lead to nutrient leeching from hay and result in an imbalanced diet. Vitamin and mineral supplementation is particularly important if you are feeding soaked hay.
Steaming is more effective for improving the hygienic quality of hay by eliminating allergens and microbial contaminants. Steaming is recommended for horses with respiratory issues, allergies or immune complications.
A hay sample is a always a good first step when considering any changes to your feeding program. This is the only way to determine the NSC content of your hay and whether soaking is warranted.
To help you decide whether to steam or soak your horse’s hay, contact our nutritionists for a free consultation.
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