Beef Cattle Forage Quality Testing: How to Sample and Interpret Results

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-14

Key Takeaways

• Forage quality is highly variable and significantly impacts beef cattle nutrition, reproduction, and health; testing is crucial for cost-effective supplementation, preventing deficiencies like low crude protein (CP < 7% for rumen function) or energy (Total Digestible Nutrients - TDN < 50%), and avoiding toxicities such as nitrates (>1000 ppm DM).
• Representative sampling is paramount: use a hay probe to collect 15-20 cores per lot (defined by forage type, cutting, or field), combine them in a clean bucket, and submit approximately one pound to the laboratory, ensuring samples are taken 2-4 weeks before sale or feeding.
• Standard laboratory analyses should include Dry Matter (DM), Crude Protein (CP), Acid Detergent Fiber (ADF), Neutral Detergent Fiber (NDF), and TDN; for annual forages or drought-stressed crops, nitrate testing is essential due to accumulation risks.
• Interpret results by comparing forage nutrient levels to specific animal requirements (e.g., lactating cows need 10-12% CP and higher energy than dry cows), using ADF to predict digestibility and NDF to estimate dry matter intake (DMI ≈ 120/NDF%).
• Supplementation should directly address measured deficiencies identified by forage testing and animal requirements; for example, low CP necessitates rumen-degradable protein sources, while low TDN requires energy supplements like corn or barley, introduced gradually to prevent acidosis.

Forage is the foundation of every beef cattle operation, yet most producers never test what they feed. Hay and silage vary widely in nutrient content depending on plant species, maturity at harvest, soil fertility, and storage conditions. Feeding untested forage is like balancing a checkbook without knowing the balances. This guide explains exactly how to collect a representative forage sample, what laboratory tests to request, how to read the results, and how to use those numbers to build a cost-effective supplementation program. It is written for cow-calf producers, stocker operators, and anyone who buys or sells hay in commercial quantities.

At a Glance

• Test every cutting or field separately. Never mix samples from different fields, cuttings, or forage types.
• Use a hay probe that is at least 12 inches long and 3/8 inch inside diameter. Coring is the only accurate way to sample baled hay.
• Collect 15 to 20 cores per lot. Combine them in one clean bucket, mix thoroughly, and send about one pound to the lab.
• Sample hay within 2 to 4 weeks of harvest if you plan to sell it. Sample stored hay 2 to 4 weeks before feeding.
• Request a standard nutrient package that includes crude protein, ADF, NDF, TDN, and key minerals. Add nitrate testing for annual forages or drought-stressed crops.
• Interpret results relative to the animal that will eat the forage. A lactating cow needs more protein and energy than a dry cow in mid-gestation.
• Use forage test results to design a supplementation program. Every pound of supplement should correct a measured deficiency, not a guessed one.
• Keep records for at least three years. Compare results across cuttings, fields, and years to spot trends in soil fertility or harvest timing.
• If forage tests indicate a problem you cannot explain, contact your local cooperative extension office or a veterinary nutritionist before making major changes.

Why Forage Quality Testing Matters

Beef cattle forage testing is the single most cost-effective management tool available to a cow-calf producer. A single hay test costs between $15 and $40 depending on the lab and the package you request. The information from that test can save hundreds of dollars per ton in wasted supplement, prevent reproductive failures from nutritional deficiencies, and help you avoid the catastrophic losses that come from feeding moldy or nitrate-toxic forage.

Forage quality is not a fixed property. It changes constantly. A grass hay field cut in early boot stage might test 16 percent crude protein and 58 percent TDN. The same field cut at full bloom might test 8 percent crude protein and 50 percent TDN. Wait until the seed heads are fully mature and you might be looking at 5 percent crude protein and 42 percent TDN. The difference between those numbers is the difference between a heifer that breeds on time and a cow that comes up open at pregnancy check.

The economics are straightforward. Hay typically represents 40 to 60 percent of the annual cost of keeping a beef cow. If you are feeding 40 pounds of hay per cow per day for 120 days of winter, that is 4,800 pounds of hay per cow per year. A difference of 2 percentage points in crude protein means the difference between buying 100 pounds of supplemental protein or not. At current supplement prices, that is often $20 to $40 per cow per year. For a 100-cow herd, that is $2,000 to $4,000 that you either spend or save based entirely on what a forage test tells you.

Forage testing also protects you from hidden dangers. Nitrate accumulation in drought-stressed annual forages can kill cattle in a matter of hours. Moldy hay can cause respiratory disease and mycotoxin poisoning. Poorly fermented silage can harbor Clostridium bacteria that cause fatal disease within days of feeding. A forage analysis that includes the right tests can flag these risks before you put the feed in front of your animals.

Understanding What the Lab Measures

Before you can interpret a forage test report, you need to understand what each number means. The standard forage analysis measures several components. Each one tells you something different about how that forage will perform in your herd.

Dry Matter and Moisture

Dry matter is the percentage of the sample that is not water. Fresh pasture might be 20 percent dry matter. Hay should be 88 to 92 percent dry matter. Silage is typically 30 to 45 percent dry matter. All other nutrient values are reported either as-fed or on a dry matter basis. Always compare forages on a dry matter basis. Otherwise you are comparing apples to oranges.

To convert an as-fed value to dry matter basis, divide the as-fed percentage by the dry matter percentage and multiply by 100. For example, if a hay tests 10 percent crude protein as-fed and 90 percent dry matter, the dry matter protein is 10 divided by 0.90, which equals 11.1 percent.

Crude Protein

Crude protein is an estimate of the total protein content of the forage. It is calculated by measuring the nitrogen content and multiplying by 6.25. This assumes that protein is about 16 percent nitrogen. The crude protein value includes both true protein and non-protein nitrogen such as nitrates and urea.

Mature beef cows in mid-gestation need about 7 to 8 percent crude protein in their total diet. Lactating cows need 10 to 12 percent. Growing replacement heifers need 12 to 14 percent. Most grass hays harvested at the right stage will meet the needs of dry cows but fall short for lactating cows or growing animals.

ADF and NDF

Acid detergent fiber and neutral detergent fiber are the two most important structural carbohydrate measurements in a forage test. They tell you about the fiber content and, by extension, the digestibility and energy value of the forage.

NDF measures the total cell wall content of the plant. This includes cellulose, hemicellulose, and lignin. As plants mature, NDF increases. High NDF means the forage is bulky and the animal cannot eat as much of it. NDF also predicts dry matter intake. A general rule is that dry matter intake as a percentage of body weight equals 120 divided by the NDF percentage. If your hay has 60 percent NDF, cows will eat about 2 percent of their body weight in dry matter. If NDF drops to 40 percent, intake can rise to 3 percent.

ADF measures the cellulose and lignin portion of the cell wall. ADF is highly correlated with digestibility. As ADF increases, digestibility decreases. ADF is used to calculate energy values such as TDN. Legume hays typically run 30 to 40 percent ADF. Grass hays run 35 to 45 percent ADF. Values above 45 percent indicate very mature, low-quality forage.

TDN and Energy Values

Total digestible nutrients is an estimate of the energy content of the forage. It is usually calculated from ADF using a regression equation. A common formula is TDN percent equals 88.9 minus 0.779 times ADF percent. So a hay with 40 percent ADF would have a TDN of about 57.7 percent.

Some labs now report net energy values instead of or in addition to TDN. Net energy for maintenance, gain, and lactation are more precise for ration balancing. If your lab reports these values, use them. If not, TDN is adequate for most cow-calf decisions.

Minerals

The standard forage test usually includes calcium, phosphorus, magnesium, potassium, and sometimes sulfur. These are the macrominerals most likely to be deficient or imbalanced in beef cattle diets. Trace minerals like copper, zinc, and selenium require a separate test and are often not included in the basic package.

Calcium and phosphorus are particularly important for breeding herds. The ideal calcium to phosphorus ratio in the total diet is between 1.5 to 1 and 2 to 1. Legume hays are high in calcium and can create a wide ratio. Grain-based supplements are high in phosphorus. Grass hays are often adequate in calcium but marginal to deficient in phosphorus.

Nitrates

Nitrate testing is essential for annual forages like sorghum, sudan, millet, corn stalks, and any forage that has been stressed by drought, frost, or heavy nitrogen fertilization. Nitrates accumulate in the lower portion of the plant when growth is slowed but nitrogen uptake continues.

Nitrate levels above 1,000 parts per million on a dry matter basis are considered risky for pregnant cattle. Levels above 3,000 ppm are dangerous. Levels above 10,000 ppm are potentially fatal. Nitrate poisoning causes sudden death, weakness, and abortion in surviving animals.

Relative Feed Value

Some labs report a single index called Relative Feed Value. RFV compares the digestible dry matter intake of your forage to full-bloom alfalfa, which is assigned a value of 100. RFV above 100 means the forage is better than full-bloom alfalfa. RFV below 100 means it is worse.

RFV is a useful marketing tool for buying and selling hay. It is less useful for ration balancing because it does not directly measure protein or minerals. Use RFV to compare lots of hay. Use the component values to build a ration.

How to Sample Hay Correctly

The most common mistake in forage testing is poor sampling. A lab test is only as good as the sample you send. A handful of hay grabbed from the outside of a bale is not representative of the bale, let alone the entire lot. You need a hay probe, a clean bucket, and a systematic sampling plan.

Choosing a Hay Probe

A hay probe is a hollow metal tube with a cutting tip. You attach it to a drill and core into the end of a bale. The probe should be at least 12 inches long and 3/8 inch inside diameter. Longer probes, 18 to 24 inches, work better for large round bales because they reach deeper into the bale.

Do not try to sample hay by grabbing handfuls from broken bales or by pulling flakes from the outside. Surface hay is weathered and does not represent the interior of the bale. Hay that has been rained on, bleached by the sun, or moldy on the outside will test differently than the good hay inside. The probe is the only tool that gives you a true cross-section of the bale.

Hay probes are available from agricultural supply catalogs, cooperative extension offices, and some feed stores. They cost between $50 and $150. If you buy or sell hay on a regular basis, a probe pays for itself in the first season.

Defining a Lot

A lot is a group of bales that you expect to be similar. Sample each lot separately. Never combine samples from different fields, different cuttings, or different forage species. If you have 100 bales of orchardgrass from the first cutting and 100 bales of orchardgrass from the second cutting, those are two lots. If you have 50 bales of orchardgrass and 50 bales of fescue from the same field, those are two lots.

When in doubt, split the lot. It is better to test too many lots than too few. The cost of an extra test is small compared to the cost of feeding the wrong supplement to the entire herd for a winter.

How Many Bales to Core

Sample 15 to 20 bales per lot. If the lot has fewer than 20 bales, core every bale. Take one core from each bale. For large round bales, core from the curved side, not the flat end. The flat end has been exposed to weather and will not represent the bale. Insert the probe perpendicular to the bale surface, about halfway up the side.

For small square bales, core from the end of the bale, pushing the probe through the flakes. Sample bales that are not on the very outside of the stack. The outer layer of bales is more weathered than the interior.

Handling the Sample

As you take each core, place it in a clean plastic bucket. Do not use a galvanized bucket. The zinc coating can contaminate the sample and affect mineral analysis. Mix the cores thoroughly in the bucket. Break up any large pieces. Fill a one-quart resealable plastic bag with the mixed sample. Squeeze out as much air as possible and seal the bag.

Label the bag clearly with a permanent marker. Include the lot name or number, the forage type, the cutting, and the date. Write the same information on the submission form that goes with the sample. If the lab assigns sample numbers, use those on both the bag and the form.

Shipping the Sample

Send the sample to the lab as soon as possible after collection. If you cannot ship it the same day, store it in a refrigerator. Do not freeze the sample unless the lab instructs you to. Do not leave it in a hot truck or barn. Heat and moisture can change the nutrient content of the sample before it reaches the lab.

Most labs accept samples by mail or through a drop-off location. Check with your lab for specific shipping instructions. Some labs provide prepaid shipping labels. Others require you to pay postage. The cost of shipping is usually $5 to $15.

When to Sample

The best time to sample depends on what you are doing with the hay. If you are selling hay, sample it within 2 to 4 weeks of harvest. This gives you time to get the test results before you negotiate a price. If you are buying hay, ask the seller for a test report. If the seller does not have one, sample the hay before you commit to the purchase.

If you are feeding hay from your own operation, sample it 2 to 4 weeks before you plan to start feeding. This gives you time to design a supplementation program and purchase any needed supplements. Do not wait until the day you open the first bale. By then it is too late to plan.

For silage and haylage, sample at harvest and then again just before feeding. Silage continues to ferment after harvest, and nutrient values can change during storage. A sample taken at harvest tells you what you put in the silo. A sample taken at feedout tells you what you are actually feeding.

How to Sample Silage and Haylage

Silage and haylage require a different sampling approach than baled hay. The material is wetter, and it is stored in a structure that makes access difficult. The goal is the same: get a representative sample of what the animals will actually eat.

Sampling at Harvest

At harvest, take samples from the forage as it is being blown into the silo or bag. Collect a handful of chopped material every 10 to 15 minutes during filling. Combine all the handfuls in a clean bucket. Mix thoroughly. Fill a one-quart bag and label it. This sample represents the average of the entire fill.

Sampling at Feedout

At feedout, sample from the face of the silo or the end of the bag. Take small handfuls from the top, middle, and bottom of the exposed face. Collect samples from several different feeding days and combine them. Do not take a single sample from one day and expect it to represent the whole silo. The material at the top and edges of a bunker silo is often more spoiled than the material in the center.

For silage that is being fed from a bag, take samples from the loose material at the open end of the bag. Do not reach into the bag to grab material from deep inside. The loose material at the face is what the animals are actually eating.

Handling Wet Samples

Silage samples need special handling. They are wet and can spoil quickly. Ship them to the lab the same day you collect them. If you cannot ship them immediately, freeze them. The lab will need to know the dry matter content to interpret the results correctly. Most labs include dry matter analysis in the standard package.

How to Sample Pasture

Sampling pasture is more difficult than sampling hay because the animals are selectively grazing. They do not eat everything in front of them. They prefer certain plants and certain parts of plants. A pasture sample that represents what is growing is not the same as what the animals are eating.

The most practical approach for most producers is to observe animal condition and performance rather than trying to sample pasture. If cows are maintaining body condition and calves are gaining at expected rates, the pasture is meeting their needs. If animals are losing weight or calves are falling behind, the pasture is likely deficient in protein or energy.

If you need a pasture sample for diagnostic purposes, clip forage at the height the animals are actually grazing. Collect samples from several locations across the pasture. Combine them and send to the lab. Interpret the results with the understanding that the sample represents what is available, not necessarily what the animals are eating. Selective grazing means animals often consume a diet that is higher in protein and lower in fiber than the average of the pasture.

Choosing a Laboratory

Several commercial laboratories and many state university labs offer forage analysis. The cost and the specific tests included vary. Choose a lab that is certified by the National Forage Testing Association. This certification ensures the lab follows standardized procedures and participates in regular proficiency testing.

Your local cooperative extension office can recommend a lab. Many state universities operate forage testing labs that serve local producers. These labs are often less expensive than commercial labs and are familiar with local forage species.

When comparing labs, look at the standard package. Most labs offer a basic package that includes dry matter, crude protein, ADF, NDF, and TDN. Some labs include minerals in the basic package. Others charge extra. If you feed a lot of annual forages or have had nitrate problems in the past, choose a lab that offers nitrate testing and request it on every sample.

Turnaround time varies from a few days to two weeks. If you need results quickly, ask the lab about rush service. Some labs charge extra for faster turnaround. Plan ahead so you are not paying rush fees.

Reading a Forage Test Report

A forage test report looks intimidating at first glance, but the layout is logical. Most labs report each nutrient as a percentage on a dry matter basis. Some labs also report as-fed values. Always use the dry matter basis for comparison and ration balancing.

A Sample Report

Here is an example of a typical forage test report for a grass hay lot:

What does this report tell you? The crude protein of 9.4 percent is adequate for a dry cow in mid-gestation but below the 10 to 12 percent needed by a lactating cow. The TDN of 56.8 percent is adequate for dry cows but marginal for lactating cows. The NDF of 62.5 percent predicts dry matter intake of about 1.9 percent of body weight. The calcium to phosphorus ratio is 2.3 to 1, which is acceptable. The RFV of 87 tells you this is average quality hay, slightly below full-bloom alfalfa.

Comparing to Animal Requirements

The next step is to compare the forage test results to the requirements of the animals that will eat the forage. The National Research Council publishes detailed nutrient requirements for beef cattle. Your extension office can provide a copy or direct you to an online calculator.

For a dry, mature beef cow in mid-gestation weighing 1,200 pounds, the daily requirements are roughly:

• Dry matter intake: 24 to 27 pounds
• Crude protein: 1.9 to 2.2 pounds
• TDN: 11 to 13 pounds
• Calcium: 0.04 to 0.05 pounds
• Phosphorus: 0.03 to 0.04 pounds

Using the example hay above, a cow eating 25 pounds of dry matter would consume 2.35 pounds of crude protein and 14.2 pounds of TDN. This hay easily meets the needs of a dry cow.

For the same cow in early lactation, the requirements jump to roughly:

• Dry matter intake: 32 to 36 pounds
• Crude protein: 3.5 to 4.0 pounds
• TDN: 18 to 21 pounds
• Calcium: 0.10 to 0.12 pounds
• Phosphorus: 0.06 to 0.08 pounds

The same hay would provide 3.0 pounds of crude protein and 18.2 pounds of TDN. The cow would be short on protein and marginally short on energy. She would need supplementation to maintain milk production and body condition.

Identifying Deficiencies

The forage test tells you what is in the feed. The animal requirement tells you what the animal needs. The difference between the two is your supplementation target.

If crude protein is deficient, you need a protein supplement. Common options include commercial protein blocks, dried distillers grains, soybean meal, or alfalfa hay. If energy is deficient, you need an energy supplement such as corn, barley, or a high-energy commercial feed. If both are deficient, you need a combined supplement.

If calcium and phosphorus are deficient, you need a mineral supplement. The ratio matters as much as the absolute levels. Too much calcium relative to phosphorus can interfere with phosphorus absorption. Too much phosphorus relative to calcium can cause urinary calculi in steers.

Common Mistakes in Forage Testing

Sampling Only the Best Bales

It is human nature to pull a sample from the best-looking bales in the lot. This gives you a false sense of security. The test results will look better than the actual average of the lot. When you feed the poorer bales, the animals will perform worse than expected.

Sample bales at random. Do not select bales based on appearance. If you are sampling a stack, sample bales from the top, middle, and bottom of the stack. Sample bales that were harvested at different times of the day and from different areas of the field.

Combining Samples from Different Lots

Combining samples from different fields or cuttings saves money on lab fees but produces a meaningless average. The average does not tell you what any individual lot contains. You cannot design a supplementation program for a blended sample because you do not know which bales are high quality and which are low quality.

Test each lot separately. If you have limited funds, test the lots you plan to feed first and the lots you plan to feed to your most vulnerable animals. Priorities are replacement heifers, lactating cows, and young calves.

Sampling Hay That Has Been Rained On

Hay that was rained on after cutting has lost soluble nutrients through leaching. The protein and energy values will be lower than hay that was harvested without rain. If you sample rain-damaged hay, the test results will reflect the damage. That is useful information, but it does not tell you what the hay would have been worth if it had not rained.

Sample the hay as it will be fed. If the outside of the bale is weathered and you plan to feed the whole bale, the weathered portion is part of what the animals will eat. If you plan to remove and discard the weathered outside layer, sample only the good interior.

Misinterpreting Dry Matter

Forage test reports often list values both as-fed and on a dry matter basis. If you compare as-fed values from one lab to dry matter values from another lab, you will draw wrong conclusions. Always check the basis of the report before comparing numbers.

When calculating how much forage to feed, use dry matter values. A cow that needs 25 pounds of dry matter will eat about 28 pounds of hay that is 90 percent dry matter. If the hay is only 85 percent dry matter, she will need to eat about 29 pounds to get the same dry matter.

Ignoring Mineral Results

Many producers focus on protein and energy and ignore the mineral values. Minerals are just as important for reproduction and health. A cow that is marginally deficient in phosphorus will have reduced conception rates even if her protein and energy needs are met.

Pay attention to the calcium to phosphorus ratio and to the magnesium level. Low magnesium can cause grass tetany in lactating cows grazing lush spring pasture. High potassium can interfere with magnesium absorption.

Using Test Results to Build a Supplementation Program

The goal of a supplementation program is to feed the animal what it needs, not what you happen to have on hand. Every supplement should correct a measured deficiency. If the forage test shows adequate protein, do not feed a protein supplement. If the forage test shows adequate energy, do not feed grain.

Protein Supplementation

When forage crude protein falls below 7 percent, rumen function slows down. The microbes that digest fiber need nitrogen to do their job. Without enough protein in the diet, the animal cannot extract enough energy from the forage, even if the forage itself contains adequate energy.

The classic response is to feed a high-protein supplement such as cottonseed meal, soybean meal, or a commercial protein block. These supplements provide rumen-degradable protein that stimulates fiber digestion. A common recommendation is to feed 1 to 2 pounds of a 30 to 40 percent protein supplement per cow per day when forage protein is below 6 to 7 percent.

Energy Supplementation

When forage TDN falls below about 50 percent, the cow cannot consume enough dry matter to meet her energy needs. This is common with mature grass hays and straw. The solution is to feed a high-energy supplement such as corn, barley, or a commercial energy feed.

Energy supplements should be introduced gradually. Start with 1 pound per head per day and increase by 1 pound every 3 to 4 days until you reach the target. Sudden introduction of large amounts of grain can cause acidosis and founder.

Mineral Supplementation

Provide a free-choice mineral supplement that is formulated to correct the deficiencies in your forage. If your forage is high in calcium, choose a mineral with a narrow calcium to phosphorus ratio. If your forage is low in magnesium, choose a mineral with added magnesium.

Work with your extension agent or a nutritionist to select the right mineral. The mineral market is confusing, and not every product is appropriate for every operation. The cheapest mineral is not always the best value. Look at the levels of the minerals your forage is lacking.

Body Condition Scoring

Body condition scoring is the ultimate check on your feeding program. A cow in good body condition is a cow that is getting what she needs. A cow that is losing condition is not, regardless of what the forage test says.

Body condition is scored on a 1 to 9 scale. A score of 1 is emaciated. A score of 9 is obese. The target for mature cows at calving is 5 to 6. Cows that calve at a body condition score below 5 have longer postpartum intervals and lower conception rates.

Score your cows at weaning, at mid-gestation, and at calving. If cows are losing condition between weaning and calving, increase supplementation. If they are gaining condition, you may be overfeeding and can reduce supplement costs.

Monitoring and Recordkeeping

Forage testing is not a one-time event. It is a continuous process. Keep records of every test you run and compare results across years. This is the only way to identify trends in your forage quality and to evaluate the impact of changes in your management.

What to Record

For each forage test, record:

• The field or farm where the forage was grown
• The forage species and variety
• The cutting or harvest number
• The harvest date
• The weather conditions at harvest
• The fertilizer program used
• The laboratory results
• The animals that were fed the forage
• The supplementation program used
• Animal performance data such as body condition scores and pregnancy rates

How to Use the Records

After several years of records, patterns will emerge. You may notice that first-cutting hay is consistently lower in protein than second-cutting hay. You may notice that hay from a particular field is always deficient in phosphorus. You may notice that forage quality declines when you delay harvest by even a few days.

Use these patterns to make management changes. If a field consistently produces low-protein hay, adjust the fertilizer program or harvest earlier. If a particular cutting is always low in phosphorus, plan to supplement phosphorus during the months you feed that hay.

When to Retest

Retest forage whenever there is a reason to believe the quality has changed. This includes:

• A new cutting or harvest
• A new field
• A change in forage species
• A change in harvest timing
• Weather damage during harvest or storage
• Evidence of mold or heating in storage
• A change in the animals being fed

Do not assume that this year's hay is the same as last year's hay. Weather, soil conditions, and harvest timing all affect forage quality. The only way to know what you are feeding is to test it.

When to Call a Veterinarian or Extension Agent

Forage testing answers many questions, but it does not answer all of them. There are times when you need professional help to interpret results or to diagnose problems.

Call Your Extension Agent When

• You need help interpreting a forage test report
• You are designing a supplementation program and want a second opinion
• You are considering a major change in your feeding program
• You want to compare forage test results across years or fields
• You need help selecting a laboratory
• You have questions about fertilizer recommendations based on forage quality

Extension agents are trained to help producers use forage testing information. Their services are free or low cost. They have access to local data and can help you interpret results in the context of your specific operation.

Call Your Veterinarian When

• Animals are losing weight despite adequate forage and supplementation
• Animals are showing signs of nutritional deficiency such as poor hair coat, reduced fertility, or weak calves
• You suspect nitrate poisoning, mold toxicity, or other forage-related illness
• Multiple animals are sick or dying and you do not know why
• You see signs of urinary calculi in steers
• You suspect a mineral deficiency or toxicity

Your veterinarian can run diagnostic tests to confirm or rule out forage-related problems. They can also help you treat sick animals and prevent further losses.

Call Both When

• You are investigating a herd-wide health problem that might be related to nutrition
• You are developing a herd health and nutrition plan for the coming year
• You are considering changes to your breeding program that will affect nutritional requirements

Special Considerations for Different Forage Types

Legume Hays

Legume hays such as alfalfa and clover are higher in protein and calcium than grass hays. They are also more digestible. A good alfalfa hay can test 18 to 20 percent crude protein and 58 to 62 percent TDN. Legume hays are excellent for growing animals and lactating cows but can be too rich for dry cows.

The main concern with legume hays is the calcium to phosphorus ratio. Alfalfa is very high in calcium. If you feed alfalfa as the primary forage, the calcium to phosphorus ratio in the total diet can exceed 6 to 1. This can interfere with phosphorus absorption and cause reproductive problems.

Grass Hays

Grass hays are the most common forage for beef cattle in many regions. Timothy, orchardgrass, fescue, and brome are all popular choices. Grass hays are lower in protein and calcium than legume hays but are often adequate for dry cows.

The quality of grass hay depends heavily on maturity at harvest. Grass harvested in the vegetative stage can test 12 to 16 percent crude protein. Grass harvested at full maturity can test below 6 percent. The window for harvesting high-quality grass hay is narrow, often only a few days.

Annual Forages

Annual forages like sorghum, sudan, millet, and corn are commonly used for silage or hay. These forages can be high yielding but require careful management. Nitrate accumulation is a major concern, especially in drought-stressed crops.

Test annual forages for nitrates before feeding. If nitrate levels are elevated, the forage can be diluted with other feeds to reduce the risk. Ensiling can reduce nitrate levels by 30 to 50 percent, but the reduction is not guaranteed.

Straw

Straw is the lowest quality forage commonly fed to beef cattle. Wheat straw and barley straw typically test 3 to 5 percent crude protein and 40 to 45 percent TDN. Straw is only suitable for dry, mature cows in mid-gestation, and even then it requires supplementation.

If you feed straw, test it and supplement aggressively. Protein supplementation is essential to maintain rumen function. Energy supplementation may also be needed if the straw is very low quality.

Buying and Selling Hay Based on Test Results

Forage testing is a valuable tool for hay marketing. Sellers who test their hay can command higher prices because they can document quality. Buyers who test hay can avoid overpaying for low-quality forage.

If You Are Selling Hay

Sample each lot and have the results available before you advertise the hay. Include the test results in your advertisement or provide them to prospective buyers. Be honest about what the test shows. A buyer who is burned by misrepresented hay will not return.

Price your hay based on its nutrient content, not just its weight. A ton of 14 percent protein hay is worth more than a ton of 8 percent protein hay. The test results give you a defensible basis for your price.

If You Are Buying Hay

Ask the seller for a forage test report before you commit to a purchase. If the seller does not have a test report, ask if you can sample the hay before you buy. Most reputable sellers will allow this.

When comparing hay from different sellers, compare on a dry matter basis and on a cost per pound of nutrient basis. A hay that costs $180 per ton but tests 12 percent protein is a better value than a hay that costs $150 per ton but tests 8 percent protein. Do the math before you buy.

Frequently Asked Questions

How much does a forage test cost?

A basic forage test that includes dry matter, crude protein, ADF, NDF, and TDN typically costs $15 to $30. Adding minerals increases the cost to $25 to $40. Nitrate testing adds $5 to $15. The cost of the test is small compared to the cost of the feed it evaluates. A single test can save you hundreds of dollars in unnecessary supplement or prevent a costly herd health problem.

How many bales should I sample for a reliable test?

Sample 15 to 20 bales per lot. If the lot has fewer than 20 bales, sample every bale. Take one core from each bale and combine the cores into a single sample. This gives you a representative average of the lot. Sampling fewer bales increases the risk that your sample does not represent the true average of the lot.

Can I test hay that is already being fed?

Yes. If you are already feeding a lot of hay and want to know what it is providing, sample it as you feed it. Core the bales before you feed them, just as you would at any other time. The results will tell you what the animals are actually consuming. This information can help you adjust supplementation for the remainder of the feeding period.

What is the difference between ADF and NDF?

ADF measures the cellulose and lignin in the plant cell wall. It is used to estimate digestibility and energy content. NDF measures the total cell wall, including hemicellulose. It is used to estimate dry matter intake. As plants mature, both ADF and NDF increase, meaning the forage becomes less digestible and the animal can eat less of it.

Why does my hay test show different protein than the seller claimed?

Forage quality varies within a field, within a cutting, and even within a single bale. The seller may have sampled a different lot or may have sampled only the best bales. Weather conditions during harvest, storage conditions, and sampling technique all affect test results. If you are buying hay, sample it yourself or ask to see the lab report for the specific lot you are purchasing.

How often should I test my hay?

Test every lot of hay you plan to feed. A lot is a group of bales from the same field and cutting. If you harvest multiple cuttings from the same field, test each cutting separately. Test again if the hay has been stored for more than a year or if you suspect spoilage. For silage, test at harvest and again at feedout.

What nitrate level is dangerous for cattle?

Nitrate levels below 1,000 parts per million on a dry matter basis are generally safe. Levels between 1,000 and 3,000 ppm are risky for pregnant cattle and should be diluted with other feeds. Levels above 3,000 ppm are dangerous and should not be fed free choice. Levels above 10,000 ppm are potentially fatal. If you suspect nitrate problems, test before feeding.

Do I need to test minerals separately?

The standard forage test usually includes calcium, phosphorus, magnesium, and potassium. These are the macrominerals most likely to be deficient. Trace minerals like copper, zinc, and selenium require a separate test. If you have had trace mineral problems in your herd, or if your region is known for trace mineral deficiencies, request a trace mineral analysis.

Related Farming Guides

This section will be populated with links to related farming guides on beef cattle nutrition, hay production, pasture management, and herd health. Check back for updates.

Related Clinical & Scientific Guides

• Cattle Head Gate Selection and Adjustment
• Beef Cattle Handling Facility Flow
• Beef Cattle Maternity Pen Design: Comfort and Monitoring

References

• Beef Cattle Research Council: https://www.beefresearch.ca/
• USDA APHIS Cattle Health: https://www.aphis.usda.gov/livestock-poultry-disease/cattle
• WOAH Terrestrial Animal Health Code: https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/
• FAO Animal Production and Health: https://www.fao.org/animal-production/en/
• WOAH (World Organisation for Animal Health): https://www.woah.org/en/home/

This article is educational and is not a substitute for veterinary diagnosis, treatment, public-health guidance, or regulatory reporting.