How to test the quality of your hay?

Published 14th October 2021
Feeding Health and Welfare All Studies

Hay quality is critically important, especially for animals having high nutritional requirements, and the ultimate test of hay quality is animal performance. Hay quality is considered satisfactory when animals consuming it perform as desired. However, in our last article, we found that laboratory testing hay was a crucial part of a farm/ranch’s strategy in order to optimise the herd’s health while mitigating the costs of your feeding programme.

Sampling and testing hay for quality can help to design your feeding programme. Photo credit Troy Walz.

As you know, the factors that affect hay quality include: growing conditions, fertility, species, varieties, pests, presence of weeds, harvesting, curing, handling, storage and feeding.

Before we drill into today’s subject, an important thing to remember is that the storage conditions can have a dramatic effect on hay chemical composition and feeding value. We will elaborate on this specific topic in a future article, but keep in mind that the hay you tested at the beginning of the season could not get the same testing results at the end of the season due to, amongst various reasons, storage conditions.

How to evaluate hay quality?

Several methods exist for evaluating hay quality: visual, chemical, near-infrared reflectance spectroscopy (NIRS), and animal performance. Visual estimates can help but vary considerably.

Descriptions based on these estimates show high-quality hay to be early cut, leafy, soft, free of mold and foreign material and having a pleasant odor. Color can be misleading, because hay having a bright green color may be mature and fibrous, while faded hay may often have excellent nutritional value.

The most precise way to determine the nutrient content of hay is through laboratory analysis. If a representative sample is taken and analyzed for nutritive content, the results can help determine how much and what type of supplementation, if any, is needed in order to meet the nutrient requirements of the animals being fed, and to obtain the level of performance desired. This leads to efficient and economical feeding programs.

How to sample hay for laboratory quality analyses?

Taking a proper and representative sample is the most important factor in correct forage analysis. While laboratory analysis can determine the quality of a submitted sample, if the submitted sample does not represent fully the quality of an entire lot, a correct analysis cannot be determined. Bales within a lot of hay should be sampled at random. 

A sample should be taken for each lot of hay. A “lot” represents a group of bales of hay that were grown in the same field, harvested under the same conditions and at the same time, and stored in the same way. If two lots of hay are in a stack, sample them separately.

When collecting samples, a hay/forage probe should be used which has a minimum cutting diameter of 1,5 cm (or 1/2 inch) and a minimum length of 30 cm (12 inches). Open the bales gently (you do not want to lose the leaf matter in your sample). Firmly grab a sample out of the slab and use the scissors to cut each side of the hay, so you are left with a handful of hay sample.

Samples should be taken from the ends of conventional rectangular bales or from the radial sides of large round bales. A minimum of 20 core samples are recommended for a lot of 10 tons or more.

Samples should be stored in an airtight bag for shipment to the laboratory. A sampling of weathered (exterior portion of the bale) hay for nutritive value is more complex than sampling unweathered (interior portion of the bale) hay. Ideally, weathered and unweathered portions of bales should be sampled separately and the analysis results from the two fractions weighted according to their relative contributions to entire bales.

How to read hay laboratory analysis?

At first glance, your hay analysis report may be intimidating. You will see a large collection of numbers, usually arrayed in two columns labeled as “As Fed” or “As Samples” and “Dry Matter”.

For the purposes of evaluating the hay for your livestock, you will most often consult the “Dry Matter Basis” column. Both sets of numbers represent the actual amount of the specific nutrient in the hay, but the “As Fed”/”As Sampled” column is reported with the values expressed as a percentage of the feed including the weight of the moisture in it. The “Dry Matter” column is reporting the nutrients expressed as a percentage of the feed without the moisture included. 

In order to accurately compare the inputs into your livestock’s diet of one feed component relative to another, it is important to compare them on a dry matter basis so that the nutrients they contribute are not being “diluted” in percentage by the moisture present in the feed.

Ideally, grass or alfalfa hay should be 90 percent or more dry matter, indicating the presence of 10 percent moisture or less. More than 10 percent moisture in a hay sample could indicate a higher risk for mold or heating in the bales.


DRY MATTER (DM) The percentage of a plant sample that remains after all water has been removed.

DIGESTIBLE DRY MATTER INTAKE (DDMI) An estimate of how much DDM an animal will consume in a given period of time. It is calculated as follows: DDM X DMI/100.

DRY MATTER INTAKE (DMI) This is the amount of forage an animal will eat in a given period of time. Estimates of DMI are based on results from animal feeding trials and the measured NDF concentration of a forage or feed.

DIGESTIBLE DRY MATTER (DDM) The percentage of a sample that is digestible. DDM is a calculated estimate based on feeding trials and from the measured ADF concentration.

CRUDE PROTEIN (CP) The total quantity of true protein and nonprotein nitrogen present in plant tissue. This can be calculated by multiplying the nitrogen fraction by 6.25. In ruminants, evaluation of the fraction that is degradable in the rumen, degradable intake protein (DIP), versus the rumen-undegradable fraction, undegradable intake protein (UIP), is also important. However, the rumen degradability of protein is not measured in most commercial labs. Therefore, it is recommended that rations be formulated using analyzed CP values and average values for DIP and UIP.

HEAT DAMAGED PROTEIN OR INSOLUBLE CRUDE PROTEIN (ICP) Nitrogen that has become chemically linked to carbohydrates and thus does not contribute to either DIP or UIP supply. This linkage is mainly due to overheating when hay is baled or stacked with greater than 20% moisture, or when silage is harvested at less than 65% moisture. Feedstuffs with high ICP are often discolored and have distinctly sweet odors in many cases. When the ratio of ICP:CP is 0.1 or greater, meaning more than 10% of the CP is unavailable, the crude protein value is adjusted. Adjusted crude protein (ACP; see below) values should be used for ration formulation.

ADJUSTED CRUDE PROTEIN (ACP) Crude protein corrected for ICP. In most nutrient analysis reports, when ACP is greater than 10% of CP, the adjusted value is reported. This value should be used in formulating rations when ICP:CP is greater than 0.1.

DIGESTIBLE PROTEIN (DP):  Reported by some laboratories, do not use without the guidance of a nutritionist. Digestible protein values are not needed for most ration formulation because nutrient requirements and most formulation tools are already adjusted for protein digestibility. Furthermore, protein digestibility is influenced by external factors.

CRUDE FIBER (CF) Crude fiber is a traditional measure of fiber content in feeds. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) are more useful measures of feeding value and should be used to evaluate forages and formulate rations.

NEUTRAL DETERGENT FIBER (NDF) The percentage of cell walls or other plants structural material present. This constituent is only partially digestible by animals. Lower NDF levels are generally associated with higher animal intake.

ACID DETERGENT FIBER (ADF) The percentage of highly indigestible plant material. Higher ADF levels are generally associated with lower digestibility.

IN VITRO DIGESTIBLE DRY MATTER (IVDDM) is a similar term which indicates that the digestibility level was determined via a laboratory test as opposed to one which utilized live animals fitted with a port open to the rumen which allows digestion of small samples inside the animal.

TOTAL DIGESTIBLE NUTRIENTS (TDN) The sum of the digestible fiber, protein, lipid, and carbohydrate components of a feedstuff or diet. TDN is directly related to digestible energy and is often calculated based on ADF. TDN is useful for beef cow rations that are primarily foraging. When moderate to high concentrations of concentrate are fed, net energy (NE, see below) should be used to formulate diets and predict animal performance. TDN values tend to underpredict the feeding value of concentrate relative to forage.

NET ENERGY (NE) Mainly referred to as net energy for maintenance (NEm), net energy for gain (NEg), and net energy for lactation (NEl). The net energy system separates the energy requirements into their fractional components used for tissue maintenance, tissue gain, and lactation. Accurate use of the NE system relies on the careful prediction of feed intake. In general, NEg overestimates the energy value of concentrates relative to roughages.

ETHER EXTRACT (EE) The crude fat content of a feedstuff. Fat is an energy source with 2.25 times the energy density of carbohydrates.

RELATIVE FEED VALUE (RFV) A measure of a forage’s intake and energy value. It compares one forage to another according to the relationship DDM X DMI/100 divided by a constant. RFV is used to evaluate legume hay. RFV is often used as a benchmark of quality when buying or selling alfalfa hay. RFV is not used for ration formulation.

RELATIVE FORAGE QUALITY (RFQ):  Like RFV, RFQ combines predicted intake (NDF) and digestibility (ADF). However, RFQ differs from RFV because it is based on estimates of forage intake and digestibility determined by incubating the feedstuff with rumen microorganisms in simulated digestion. Therefore, it is a more accurate predictor of forage value than RFV. Neither RFV nor RFQ are used in ration formulation.

MINERALS AND MACRO-ELEMENTS Macro-elements are those required in relatively large amounts. This group consists of calcium, phosphorus, magnesium, sulphur, potassium and salt (sodium chloride). The requirements for macro-minerals vary depending on the class of animal, and the level and region of production. Daily nutrient requirements of livestock during different stages of production can be found online on local forage/livestock associations or universities’ websites.


Applying hay analysis on the farm/ranch

Review your forage analysis results to determine overall quality on a dry matter basis.

Compare the expected dry matter intake, total digestible nutrients, protein, calcium, and phosphorous values to the nutrient requirements of your herd (again, lots of data are available online on local forage/livestock associations or universities’ websites).

If forage/hay report values are less than the daily nutrient needs, additional supplemental feeds may be needed in the diet. Your nutrition agent or your vet can provide more information and help you to develop balanced rations/diets for your herd.


Remember that your feeding method is also important to deliver and preserve the highest quality hay possible. Find out more on our previous #FeedGrassForGood articles: