Why Testing Hay Is Important and Understanding Hay Analysis Results

Horses are naturally designed to thrive on a forage-based diet, with pasture and hay serving as the ideal foundation for optimal nutrition. 

While hay is a significant component of the horse’s diet, it’s often the least understood, as it lacks the readily available Guaranteed Analysis (GA) that full intake horse feeds, ration balancers and supplements have.

In this article, you'll gain a better understanding of why hay testing is crucial for your horse’s health and how to interpret hay analysis results. 

Why Testing Hay is Important

While many horse owners recognize that high-quality hay smells pleasant, feels soft, and contains more leaves than stems, these visual cues don't always reflect the actual nutrient content. There is a more consistent and accurate way to determine the levels of crude protein, starch, and other essential nutrients in a bale of hay. This can be accomplished by conducting a hay analysis.

Testing hay allows for a more definitive assessment of a horse’s diet composition. A hay analysis is a helpful tool in many situations, including the following:

• A horse is not performing as expected

• Breeding operations

• Managing horses with metabolic conditions, such as Insulin Resistance, Polysaccharide Storage Myopathy (PSSM), and Recurrent Exertional Rhabdomyolysis (RER)

For horses with metabolic conditions, equine nutritionists commonly recommend a diet with limited non-structural carbohydrate (NSC) intake—making hay testing even more valuable for these horses. 

The Hay Testing Process

The hay testing process starts with collecting a sample from each load of hay. Be mindful that sampling a single bale or taking samples from several bales does not provide a complete analysis of the average nutrients across the entire load of hay. Hay from different suppliers and even different cuttings from the same supplier should be tested separately.

A hay probe can be used to collect a core sample from 10 bales or 10% of the hay load—whichever is greater. Samples should be taken from the small end of square bales and the round side of round bales. You can purchase a hay probe or borrow one from your county extension office if you don’t already own one. The samples you take from multiple bales are then combined in a sealable plastic bag and mailed to a commercial laboratory for testing. 

While numerous labs offer forage testing services, ensure that they are familiar with equine nutrients for accurate hay testing. Some labs make this very easy by providing equine-specific packages. A testing package designed for livestock species may not provide all the necessary information required to evaluate hay for horses.

Understanding Hay Analysis Results

Interpreting a hay analysis can be challenging, as the results often contain abbreviations, numbers, and percentages that may leave horse owners uncertain about which values are considered good or bad. It can be helpful to break down the meanings of these abbreviations, identify typical nutrient values, and have them handy when reading through the hay analysis.

It’s also important to note that most hay analyses include two columns of nutrient values. One column is labeled "as is" or "as fed," which reflects the nutrient content of the hay in its natural state — the way it would be fed to a horse. The other column is labeled "DM," meaning Dry Matter, which represents the nutrient content after all moisture has been removed from the sample. The DM column enables a more accurate comparison between different forage types, such as pasture and hay, and it eliminates the variability caused by water content. Unless otherwise stated (except for moisture values), the nutrient values referenced in the analysis are typically reported on a DM basis.

Other essential aspects of understanding a hay analysis include:

Moisture: Optimal moisture levels range from 10% to 16%. If the moisture content is below 10 percent, the hay becomes excessively dry, leading to significant leaf loss due to shattering and reduced palatability. 

Overly dried hay tends to be brittle, and in the case of alfalfa, this brittleness results in a high degree of leaf shatter, further diminishing its nutritional value. Hay with a moisture content above 16 percent is more likely to develop mold unless a preservative is used during baling. If the moisture exceeds 18 percent, the risk of mold increases significantly, and at levels above 20 percent, there is even a danger of spontaneous combustion.

Crude Protein: For adult horses, adequate protein levels are typically provided when the crude protein (CP) content in hay is around 10 to 12 percent. However, young horses, performance horses undergoing high-intensity exercise, and lactating broodmares may benefit from a higher percentage of crude protein in their forage. 

The type of hay also influences CP levels, with legumes like alfalfa generally containing higher CP levels (15–20%) compared to grass hays (7–14%). Additionally, the maturity of the plant at harvest affects CP levels, which is why testing hay is essential to determine its accurate nutrient content. Generally, hay with a crude protein level of 12 percent or higher is suitable for most horses, while hay with a crude protein level of less than 10 percent is considered low quality.

Fiber: Carbohydrates in hay are divided into two categories: structural carbohydrates (fibers) and non-structural carbohydrates (sugars, starch, fructans, etc.). The fiber content and quality of the hay are determined by NDF (neutral detergent fiber) and ADF (acid detergent fiber) values, which provide insight into forage maturity and digestibility. 

NDF measures cellulose, hemicellulose, and lignin, while ADF measures cellulose and lignin. As forage matures, NDF and ADF levels increase, making the hay less digestible and less palatable for horses.

For horses that need to lose weight or are easy keepers, higher ADF and NDF values within the ideal range are preferable, as these forages provide fewer calories. Conversely, young, growing horses and those in hard work will benefit from hay with lower ADF and NDF values to meet their higher calorie demands. 

Monitoring ADF and NDF levels helps ensure that the hay selected aligns with the horse's individual nutritional requirements. The table below shows the ADF and NDF percentage ranges and how they affect hay quality: 

*Refusals or significant intake reductions are observed with hay containing more than 65% NDF and 45% ADF.

Non-Structural Carbohydrates: Non-structural carbohydrates (NSC) refer to the starch and sugar content in feedstuffs. NSC in hay is calculated as WSC (water-structural carbohydrates) plus starch. WSC is comprised of sugars and fructans—a significant storage carbohydrate of forages. Horses that are sensitive to NSC benefit from low (<12%) to ultra-low (<10%) hay, depending on the individual level of sensitivity. Forage is the primary source of non-structural carbohydrates (NSC) in many horses’ diets.

Calcium and Phosphorus: The total diet (forage plus horse feed) calcium-to-phosphorus ratio should be less than 3:1 for mature horses. Growing horses, as well as pregnant and lactating mares, should be fed a diet with a calcium-to-phosphorus ratio of 2:1 to 1:1 to minimize the likelihood of Developmental Orthopedic Disorders.

Other Information on a Hay Analysis

A hay analysis can provide more information than what is mentioned above. It can reveal the levels of other various vitamins and minerals in the forage, which can be particularly useful when balancing a horse’s diet based on specific health conditions. 

The analysis may also include values for “ether extract fat”, which measures the fat content in the hay. However, since forage is naturally low in fat, this value is generally not a significant concern when evaluating hay quality.

Another value that may be on the analysis is RFV (Relative Feed Value), which is primarily used in cattle nutrition to estimate the quality of hay. A value of 100 represents good-quality alfalfa hay, with higher RFV values indicating better digestibility for ruminants, such as cows, which differ from horses, who are hindgut fermenters. For horse owners, the forage testing laboratory may offer different levels of analysis packages, allowing selection based on specific needs.

It’s essential to remember that ideal nutrient levels vary based on the individual horse and are influenced by factors such as health status, activity level, age, and body condition score.

Key Takeaways

A hay analysis provides valuable insights into the nutrient content of a horse's forage, helping ensure a well-balanced diet. It's crucial to select hay based on your horse’s specific needs, as not all horses require high-energy, high-protein hay. 

For horses with conditions such as chronic laminitis, equine metabolic syndrome, or obesity, a hay analysis is crucial for effectively managing these diseases. If you're unsure of how to balance your horse's diet, consulting with an equine nutritionist is highly recommended.

To ensure accurate results, follow the instructions provided by your forage testing laboratory when collecting a hay sample. If you don’t have access to a hay corer, your local extension office may have one available for loan or can assist with sample collection. A list of certified forage testing laboratories can be found on the National Forage Testing Association website.

If you need assistance interpreting your hay analysis or developing a personalized feeding plan with the help of an equine nutritionist, please don't hesitate to contact us.