Lately, more and more producers have been reaching out to Extension with a recurring concern: “I need to test my hay, but what exactly should I be testing for, and where should I send it?” This guide helps answer those questions.

Why test forage?

The purpose of a forage test is to determine the nutritional content of your hay or pasture. This includes moisture, protein, fiber, minerals, and energy levels—key components that affect animal intake and performance. With reliable lab results, you can make informed feeding decisions, plan your rations more accurately, and even price or market your hay more effectively.

Forage testing is also a critical step when dealing with specific challenges like low conception rates, poor weight gains, or inconsistent milk production. Sometimes, the problem isn’t the animals, it’s the feed. As shown in several studies, even a 2% misjudgment in crude protein (CP) can add significant feed costs or reduce milk and weight gains.

Forage quality classification

According to the University of Minnesota Extension, the USDA Agricultural Marketing Service has established standardized hay quality designations. These classifications are utilized in hay auction reports to create consistent and recognizable categories that can be applied nationwide.

Notes:

• Supreme: Very early stage prior to blooming. This type of hay is extremely leafy with soft, fine stems. It has excellent color, shows no signs of damage, and offers strong potential for high nutritional value.
• Premium: Early stage, mostly before blooming in legumes and before heading in grasses. This type of hay is exceptionally leafy with fine stems. It is green, free from damage, and has strong potential for high nutritional value.
• Good: Early to mid-maturity, such as early-to-mid-bloom in legumes or early heading in grasses. This type of hay is leafy with mostly fine stems. It is typically green in color and largely free from damage.
• Fair: More advanced stage of maturity, such as mid- to late-bloom in legumes or when grasses have headed. Hay typically contains fewer leaves and has thicker, coarser stems. It may also exhibit slight discoloration.
• Utility: Hay that falls short of the outlined standards or appears coarse and stem-heavy with mature seed heads may show noticeable discoloration and could contain mold or a musty odor. It is appropriate only for certain classes of animals with limited nutritional needs.
• *TDN (100%): Refers to the total digestible nutrients expressed on a 100% dry matter basis. This means all the moisture is removed from the forage sample when calculating the energy value. It's the standard way to compare feedstuffs fairly, regardless of their moisture content.
• **TDN (90%): Represents the total digestible nutrients adjusted to a 90% dry matter basis, which is more reflective of typical hay (since hay typically contains about 10% moisture). This format is sometimes used in practical ration formulations to better reflect what livestock actually consume.

What to test for and key forage analysis terminologies

Dry Matter (DM): This represents the portion of forage that remains after all water is removed. Since water does not contribute protein or energy, nutrient comparisons across forages are made on a dry matter basis.

Crude Protein (CP): Crude protein reflects the total nitrogen (N) content in a forage, calculated by multiplying N by 6.25, based on the assumption that protein contains about 16% nitrogen. This value includes both true protein and non-protein nitrogen, without distinguishing between usable and unusable forms.

Heat-Damaged Protein (ADIN): Protein can become less digestible when forage undergoes excessive heating, often due to rain, improper storage while wet, or poor packing of haylage. This heat alters the protein chemically, binding it within the fiber and making it less available to animals. The affected protein is measured as acid detergent insoluble nitrogen (ADIN). If ADIN exceeds 10% of the total CP, the protein value of the sample should be adjusted downward. For instance, in a sample with 12% CP, a reading over 1.2% ADIN would warrant a discount.

Fiber: Fiber consists of plant components that are less digestible and must be broken down in the rumen. While essential for rumen function, high fiber levels can limit intake and energy availability.

Crude Fiber (CF): One of the earliest methods of measuring fiber, crude fiber is no longer preferred for evaluating forage quality. Though still used on feed labels for regulatory purposes, it tends to underestimate good-quality forage and overestimate poor-quality forage.

Neutral Detergent Fiber (NDF): NDF quantifies the total structural carbohydrates (e.g., hemicellulose, cellulose, lignin), silica, and heat-damaged proteins in a plant, representing both digestible and indigestible components. It serves as an indicator of how bulky a forage is and influences dry matter intake (DMI). Lower NDF usually means higher intake potential. Typically, grasses have more NDF than legumes at the same maturity.

Acid Detergent Fiber (ADF): Is a procedure for extracting the hemicellulose component of the cell walls, leaving all the other components (lignin, silica, heat-damaged proteins).  Hemicellulose is less digestible than starches and sugars, but more digestible than cellulose. ADF is inversely related to digestibility and is commonly used to estimate forage energy content. Lower ADF values indicate greater digestibility. Total digestible nutrients (TDN) are estimated using ADF values.

Energy Estimates: Energy is a vital attribute of forage, determining how much milk or meat it can support. Energy levels can be measured in animals (in vivo), in laboratory settings (in vitro), or predicted using fiber content and mathematical models. Due to cost and time constraints, fiber-based estimations are most common.

Total Digestible Nutrients (TDN): TDN provides an estimate of all digestible components in a forage, including protein, carbohydrates, and fat, that animals can utilize for energy.

Relative Feed Value (RFV): RFV is a single-number index used to assess forage quality based on digestibility (via ADF) and intake potential (via NDF). While it doesn't express a percentage, it allows for comparison among forages. Originally developed for alfalfa, RFV can also be applied to other legumes and grasses.

Relative Feed Quality (RFQ): RFQ expands upon RFV by incorporating fiber digestibility and TDN to predict animal performance more accurately. It offers better differentiation between forage types, such as legumes and grasses, making it particularly useful for evaluating forages.

Net Energy (NE1, NEm, NEg): Net energy is the portion of energy remaining after digestion losses (in feces, urine, gases, and heat). It is categorized based on use: maintenance (NEm), weight gain (NEg), or milk production (NE1).

Near Infrared Reflectance Spectroscopy (NIR or NIRS): This rapid, computerized technique estimates forage nutrient content by analyzing how light is absorbed and reflected by a sample. Each nutrient produces a unique spectral signature, allowing for quick chemical analysis when suitable equations are available. If the results fall outside expected parameters, traditional wet lab testing is used. NIRS offers significant time savings over wet chemistry, which can take up to two weeks, while NIRS delivers results in minutes.

How to obtain a representative forage sample to send to the lab

Accurate forage testing begins with obtaining a representative and randomly selected sample. Each core must reflect the characteristics of an individual bale, and enough cores should be taken to represent the entire lot. Submitting un-cored material, like flakes, will not yield reliable results. To help ensure accurate results, follow these important steps:

1. Select a single hay lot: Obtain lots from the same cutting, variety, field, maturity stage, and harvested within a 48-hour window. Avoid mixing lots. A lot should not exceed 150–200 tons, and if you have variations in sources, divide into separate lots.
2. Use an appropriate coring tool: Choose a probe with a sharp cutting edge measuring between 3/8 inch and 5/8 inch in inside diameter. The cutting surface should be at right angles to the shaft and kept sharp to avoid compressing the sample. Avoid augers or corkscrew-type tools, as they may disproportionately collect certain plant parts.
3. Sample randomly across the stack: Walk around the stack and collect cores from bales located at different heights and locations. Avoid any pattern or preference in bale selection. The goal is to represent the entire lot evenly.
4. Collect a sufficient number of cores: In larger or more variable lots, increase the number to 20–40 cores. If you're sampling small square bales, follow the standard 20 cores from 20 bales. If you're sampling large square or round bales, aim for 20 total cores, but collected as two cores from 10 bales. If your lot is especially variable with mixed species, differing fields, and weather-influenced consider increasing to 25–40 cores per lot, whether big or small bales. 
5. Apply proper sampling technique: Insert the probe into the center of the bale’s end (not the side), at a straight angle, going 12–18 inches deep. Avoid tilting the probe or sampling from the sides.
6. Handle the sample correctly: Combine all cores from a single lot into one composite sample. Place it in a gallon zip lock bag. Keep it away from heat and sunlight, and send it to the lab promptly.
7. Maintain the right sample size: Aim for a total sample weight of about ½ pound (200 grams). If your sample exceeds this, your probe may be too wide. Oversized samples may not be processed properly in the lab. Too small a sample, on the other hand, won’t represent the lot effectively.
8. Split samples properly (if needed): If comparing lab results, send a fully ground and mixed sample to the second lab. Never divide an unground sample. Reputable labs can return a ground portion upon request for further testing, if you need to.

Here is a link to a 9-minute YouTube video on hay sampling techniques from South Dakota State University, showing you step by step on how to obtain a representative sample from all kinds of hay bales: https://youtu.be/uQT8w7bHfuA?si=IWRcysJQNL_LfFQH.

According to the University of California Cooperative Extension, when these procedures are followed, consistent and accurate results can be achieved, even when using different sampling tools or personnel. Some variation of about ±0.5% is still normal and expected.

What to look for in a hay probe and where to find one

Not all probes are built equally, and choosing the wrong one can result in inaccurate forage samples. The ideal hay probe should have a sharp cutting edge set at a 90-degree angle to the shaft, a proper diameter (between 3/8" and 5/8"), and allow for 12 to 24 inches of sampling depth. It should be able to take a clean core sample without dropping parts of the hay during removal. Probes that are too wide, too narrow, or poorly shaped may give a distorted view of your forage quality.

Below is a listing of several hay probes currently available on the market. Many of these can be ordered online or over the phone, with both hand-driven and drill-compatible options available.

Note: This list is not intended to be exhaustive and is not an endorsement of these probes, nor intends any disrespect to other probes by omission. 

Where to Test: Certified labs in the United States

The National Forage Testing Association (NFTA) certifies labs globally. Below is the complete list of NFTA-certified laboratories located in the United States as of 2025:

A full certified lab list is available at www.foragetesting.org 

References

1. Arispe, S. (2025, June 25). Understanding your forage test results. Oregon State University Extension Service. 
2. Drewitz, N., & Goplen. (n.2023). Measuring forage quality. University of Minnesota Extension. 
3. Kellems, R., & Church, D. (2010). Livestock Feeds and Feeding. Pearson.
4. National Forage Testing Association (NFTA). (2025). NFTA 2025 certified laboratory facilities. In NFTA. 
5. NFTA. (n.d.). Forage Testing. NFTA
6. Putnam, D., & Orloff, S. (1999). Proper sampling methods improve accuracy of lab testing. In California alfalfa & forage review. University of California Cooperative Extension. 
7. Putnam, D., Owens, V. & Ackerly, T.  (2023). Listing of hay probes. Cumberland Valley Analytical Services. 
8. Twidwell, E. (2015). Why test feeds? Louisiana State University. 
9. Van Saun Dvm Ms, R. (2023). Determining forage quality: Understanding Feed analysis. PennStae Extension. 
10. Zhang, H., & Redfearn, R. (n.d.). Collecting forage samples for analysis. In Oklahoma Cooperative Extension Fact Sheets (Report PSS-2589). Oklahoma Cooperative Extension Service.