Understanding Feed Analysis Reports for Livestock

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

Key Takeaways

Dry Matter (DM) is foundational for accurate ration balancing: Always convert nutrient values from an "as-fed" basis to a dry matter basis by dividing the as-fed percentage by the DM percentage to accurately compare feeds and calculate nutrient intake. For example, 8% crude protein silage at 35% DM is equivalent to 22.9% crude protein on a dry matter basis.
Crude Protein (CP) is a nitrogen-based estimate, not always true protein: CP is calculated by multiplying nitrogen content by 6.25 and includes non-protein nitrogen (NPN) which ruminants can utilize, but it overestimates true protein in forages with high NPN content like silage or urea-treated feeds.
Fiber components dictate intake and digestibility: Neutral Detergent Fiber (NDF) predicts feed intake capacity, with higher NDF leading to reduced intake due to rumen fill. Acid Detergent Fiber (ADF) predicts digestibility, with higher ADF correlating to lower energy availability.
Energy metrics like TDN and Net Energy are crucial for performance: Total Digestible Nutrients (TDN) is a common energy estimate for beef cattle, while Net Energy systems (NEM, NEG, NEL) are more precise, particularly for dairy cows, and are expressed in megacalories per unit of dry matter.
Indices like RFV and RFQ provide comparative quality assessments: Relative Feed Value (RFV) and the more advanced Relative Forage Quality (RFQ) index compare forages to alfalfa, with RFQ offering a better prediction of animal performance, especially for grasses, by incorporating fiber digestibility.
Mineral balance, particularly Calcium:Phosphorus ratio, is critical for health: The Ca:P ratio should ideally be between 1.5:1 and 2:1; legumes are typically high in calcium, while grasses are lower, necessitating careful supplementation to prevent deficiencies or imbalances like grass tetany.

Every livestock producer has stared at a feed analysis report and wondered what the numbers actually mean for the animals in the barn. A feed test is only useful if you can translate the lab results into a ration that meets your herd or flock's nutritional needs. This guide explains how to read forage testing results, understand feed test terminology, and use hay analysis interpretation to make better feeding decisions. It is written for beef and dairy cattle producers, sheep and goat farmers, horse owners, and anyone who buys or grows feed for livestock.

At a Glance

Feed analysis reports measure moisture, protein, fiber, energy, minerals, and sometimes vitamins in a feed sample.
The most important numbers for ruminants are dry matter, crude protein, neutral detergent fiber, acid detergent fiber, and total digestible nutrients.
Dry matter tells you how much actual feed is in a sample after removing water. Always balance rations on a dry matter basis.
Crude protein is a measure of nitrogen content, not actual usable protein. It overestimates true protein in forages with high non-protein nitrogen.
Neutral detergent fiber predicts how much feed an animal can eat. Acid detergent fiber predicts how digestible the feed is and relates to energy availability.
Relative feed value and relative forage quality are indexes that compare a forage to full-bloom alfalfa. They are useful for ranking lots but do not tell you the actual nutrient content.
Always test hay before buying a large quantity. Sample with a core probe, not by grabbing flakes from the outside.
Send samples to a reputable lab that uses near-infrared reflectance spectroscopy or wet chemistry methods.
Keep records of every feed test and compare results across years to spot trends in your soil, harvest timing, and storage practices.
Call your veterinarian or extension agent if animals lose condition, drop milk production, or show signs of nutritional deficiency despite a balanced ration.

Why Feed Analysis Matters

Feed is the largest variable cost on most livestock operations. You cannot manage what you do not measure. Feeding without a feed analysis is like balancing a checkbook without knowing your account balance. You might get lucky, but you will eventually make a costly mistake.

Forage quality varies widely based on plant species, soil fertility, moisture conditions at harvest, maturity stage, and storage method. The same field can produce hay with 8 percent crude protein one year and 16 percent the next. Two cuttings from the same field in the same season can differ by 5 percentage points of protein. Buying hay based on how it looks or smells is unreliable because visual appearance correlates poorly with actual nutrient content.

Feed analysis reports protect you in the hay market. When you buy hay, a lab report gives you objective data to compare prices across sellers. When you sell hay, a lab report justifies a higher price for better quality. When you feed your own hay, a lab report lets you build a ration that meets animal requirements without wasting expensive supplement.

The cost of a feed test is small compared to the cost of overfeeding or underfeeding. A standard forage test costs between 15 and 40 dollars depending on the lab and the package you choose. One round bale of hay can cost more than that. A single missed nutrient deficiency can cost far more in lost production, veterinary bills, or animal death.

How Feed Testing Works

Feed testing labs use two main methods to analyze samples: near-infrared reflectance spectroscopy (NIRS) and wet chemistry.

NIRS works by shining infrared light at a ground sample and measuring how much light is absorbed at different wavelengths. Different chemical bonds in the feed absorb light differently, and the lab uses calibration equations to convert the light patterns into nutrient estimates. NIRS is fast, inexpensive, and accurate for the components it is calibrated to measure. Most commercial forage labs use NIRS as their primary method.

Wet chemistry uses actual chemical reactions to measure nutrients. The lab dries, grinds, and weighs the sample, then uses acids, bases, and heat to isolate and measure specific components. Wet chemistry is more expensive and takes longer, but it is the reference method that NIRS calibrations are based on. Some labs offer wet chemistry as an add-on for specific components like minerals or when NIRS results look unusual.

For most producers, a standard NIRS forage test is sufficient. You do not need to specify the method when you send a sample. The lab chooses the best method for each component. What matters is that you use a reputable lab that participates in proficiency testing programs.

Several labs across the United States process feed samples for livestock producers. Many land-grant university extension services offer testing through their soil and forage testing laboratories. Private labs include Dairy One, Dairyland Laboratories, Rock River Laboratory, and others. Your local extension office can recommend a lab that serves your region.

Collecting a Representative Sample

The most accurate lab in the world cannot fix a bad sample. A feed analysis report is only as good as the sample you submit. A sample that does not represent the entire lot of feed will give you misleading numbers and lead to poor feeding decisions.

For baled hay, use a hay probe or core sampler. These are hollow metal tubes with a sharp tip that you drive into the end of a bale. The probe collects a core of hay from the inside of the bale where the quality is consistent. Do not grab flakes from the outside of a bale. The outer layer has been weathered and bleached, so it does not represent the whole bale.

Sample at least 10 to 20 bales from each lot of hay. A lot means hay that came from the same field, was cut at the same time, and was stored the same way. If you bought hay from a neighbor, sample every load or every group of bales that might differ. When in doubt, sample more rather than less.

Combine the cores from all the bales in a clean bucket. Mix them thoroughly by hand. Fill a one-quart resealable plastic bag with the composite sample. Squeeze out as much air as possible and seal the bag. Label it clearly with your name, the field name or lot number, the forage type, and the date. Keep a copy of this information in your records.

For silage and haylage, sample at the silo or pile face. Pull samples from the freshly exposed face, not from the spoiled top layer. Collect at least a handful from five to ten different locations across the face. Combine and mix these in a bucket, then fill a one-quart bag. For baled silage, core the plastic-wrapped bales the same way you core dry hay bales.

For grain and concentrates, sample from multiple bags, bins, or feeders. Use a grain probe if available. For small bags, take a handful from each bag and combine. For bins, sample from the top, middle, and bottom if you can access them safely. Never enter a grain bin to sample without proper safety equipment and someone standing by.

Ship samples immediately after collection. Moisture loss and spoilage can change the results if samples sit for days. Use a sturdy shipping box and include the submission form with your contact information and the tests you want. Most labs have prepaid shipping supplies you can request.

Key Components on a Feed Analysis Report

Feed analysis reports look different depending on the lab, but most include the same core components. Understanding what each number means is the foundation of feed analysis report interpretation.

Dry Matter

Dry matter is the percentage of the feed that is not water. It is the foundation of all ration balancing. If hay is 90 percent dry matter, then 100 pounds of that hay contains 90 pounds of actual feed and 10 pounds of water. If silage is 35 percent dry matter, then 100 pounds of silage contains only 35 pounds of actual feed.

Always convert nutrient values to a dry matter basis before comparing feeds or balancing rations. A feed that tests 10 percent crude protein on an as-fed basis might be 11 percent protein on a dry matter basis. The difference matters when you are calculating how much supplement to add.

To convert from as-fed to dry matter, divide the as-fed percentage by the dry matter percentage. For example, if silage tests 8 percent crude protein as-fed and 35 percent dry matter, the dry matter protein is 8 divided by 0.35, which equals 22.9 percent. That is a much higher protein feed than the as-fed number suggests.

To convert from dry matter to as-fed, multiply the dry matter percentage by the dry matter fraction. For example, if hay tests 15 percent protein on a dry matter basis and is 90 percent dry matter, the as-fed protein is 15 times 0.90, which equals 13.5 percent.

Crude Protein

Crude protein is calculated by measuring the nitrogen content of the feed and multiplying by 6.25. This conversion factor assumes protein is about 16 percent nitrogen. The measurement is called crude because it includes both true protein and non-protein nitrogen compounds like urea, nitrates, and free amino acids.

For most forages, crude protein is a reasonable estimate of the protein available to the animal. Ruminants can convert non-protein nitrogen into microbial protein in the rumen, so crude protein is a useful starting point. For feeds with high non-protein nitrogen, like silage or feeds containing urea, crude protein overestimates the true protein content.

Some labs also report soluble protein, degradable protein, and undegradable protein. These fractions describe how quickly protein breaks down in the rumen. They matter for high-producing dairy cows and growing animals with high protein requirements, but they are less important for beef cows, sheep, goats, and horses.

The crude protein requirement for a mature beef cow in mid-gestation is about 7 to 8 percent of the diet dry matter. A lactating beef cow needs 10 to 12 percent. A dairy cow producing 80 pounds of milk per day needs 17 to 18 percent. Growing lambs need 14 to 16 percent. Mature horses at maintenance need about 10 percent.

Neutral Detergent Fiber

Neutral detergent fiber (NDF) measures the structural components of the plant cell wall, including cellulose, hemicellulose, and lignin. These are the fibrous parts of the plant that give it structure. NDF is the best single predictor of how much feed an animal can eat because it relates to the bulk or fill of the feed.

As NDF increases, dry matter intake decreases. Ruminants have a physical limit to how much fiber they can pack into their rumen. High-NDF forages are bulky and slow to digest, so they fill the rumen before the animal has consumed enough energy to meet its needs.

Good-quality legumes like alfalfa typically have NDF values of 30 to 40 percent. Good-quality grasses have NDF values of 45 to 55 percent. Mature, stemmy forages can have NDF values above 60 percent. For lactating dairy cows, the diet should contain about 25 to 30 percent NDF. For beef cows, the diet can contain 40 to 50 percent NDF, but intake will be limited.

Acid Detergent Fiber

Acid detergent fiber (ADF) measures the cellulose and lignin portion of the plant cell wall. It is the least digestible part of the forage. ADF is inversely related to digestibility, meaning as ADF increases, digestibility decreases. ADF is used to calculate energy values like total digestible nutrients and net energy.

Good-quality alfalfa has ADF values of 25 to 30 percent. Good-quality grasses have ADF values of 30 to 40 percent. Mature forages can have ADF values above 45 percent. As ADF increases, the energy available to the animal decreases, and you need to feed more grain or other concentrates to meet energy requirements.

Total Digestible Nutrients

Total digestible nutrients (TDN) is an estimate of the total energy in the feed. It sums the digestible protein, fiber, fat, and carbohydrate fractions. TDN is expressed as a percentage of the feed dry matter.

TDN is the most commonly used energy measure in beef cattle nutrition. A mature beef cow at maintenance needs about 52 to 55 percent TDN. A lactating beef cow needs 55 to 60 percent TDN. Growing calves need 60 to 70 percent TDN depending on growth rate.

Dairy nutritionists often use net energy systems instead of TDN. Net energy for lactation (NEL) is expressed in megacalories per pound of dry matter. Good alfalfa hay has an NEL of about 0.60 to 0.65 megacalories per pound. Corn silage has an NEL of about 0.68 to 0.72 megacalories per pound.

Relative Feed Value

Relative feed value (RFV) is an index that compares a forage to full-bloom alfalfa, which is assigned a value of 100. RFV is calculated from ADF and NDF using a formula that predicts digestible dry matter and dry matter intake.

RFV = (digestible dry matter times dry matter intake) divided by 1.29

Digestible dry matter is calculated from ADF. Dry matter intake is calculated from NDF. The resulting index is useful for ranking forages and pricing hay. A forage with an RFV of 150 is 50 percent better than full-bloom alfalfa. A forage with an RFV of 80 is 20 percent worse.

RFV is most useful for comparing legumes and legume-grass mixtures. It was developed for alfalfa and works best for that crop. RFV does not account for protein or minerals, so two forages with the same RFV can have very different protein content.

Relative Forage Quality

Relative forage quality (RFQ) is a newer index that improves on RFV. RFQ uses the same framework but incorporates fiber digestibility data. It is a better predictor of animal performance, especially for grasses and warm-season forages.

RFQ is calculated using NDF, ADF, and neutral detergent fiber digestibility (NDFD). The 30-hour NDFD test measures how much of the fiber is digested in 30 hours. Forages with higher NDFD are more digestible and support higher intakes and better performance.

For legumes, RFQ and RFV give similar rankings. For grasses, RFQ is more accurate because grass fiber is generally more digestible than legume fiber at the same NDF level. If your lab offers RFQ, use it instead of RFV for grass forages.

Minerals

Most standard forage tests include calcium, phosphorus, magnesium, potassium, and sometimes sulfur. These are the macrominerals that matter most for livestock health and performance.

Calcium and phosphorus are critical for bone development, milk production, and nerve function. The calcium to phosphorus ratio should be between 1.5 to 1 and 2 to 1 for most livestock. Legumes are high in calcium, often 1.2 to 1.5 percent. Grasses are lower, often 0.3 to 0.5 percent. Phosphorus is usually 0.2 to 0.4 percent in both.

Magnesium is important for nerve and muscle function. Grass tetany, a potentially fatal condition, occurs when cattle graze lush, fast-growing grasses that are low in magnesium. If your forage tests low in magnesium, you may need to supplement.

Potassium is important for rumen function and milk production. High potassium levels can interfere with magnesium absorption. This is a concern for dry cows that are at risk of milk fever.

Nitrates

Nitrate testing is important for forages grown under drought stress or with heavy nitrogen fertilization. Plants accumulate nitrates in their stems when they cannot convert nitrogen into protein fast enough. High nitrate levels can cause nitrate poisoning in ruminants.

Nitrate levels are reported as parts per million (ppm) or as a percentage. Levels below 1,000 ppm are safe for all classes of livestock. Levels between 1,000 and 2,500 ppm are safe for non-pregnant animals but should be limited for pregnant animals. Levels above 2,500 ppm are dangerous and require dilution with other feeds. Levels above 5,000 ppm are toxic and can be fatal.

If you suspect nitrate problems, request a nitrate test on your forage samples. This is especially important for corn silage, sudangrass, sorghum, and small grain forages that have been stressed.

Understanding Energy Values

Energy is the most complex part of feed analysis interpretation because labs report it in different ways. The most common energy measures are TDN, digestible energy, metabolizable energy, and net energy.

TDN is the simplest measure and is most common on beef cattle reports. It is an estimate of the total digestible nutrients in the feed, expressed as a percentage. TDN is calculated from ADF using a regression equation, so it is only as accurate as the ADF measurement.

Net energy systems divide energy into fractions based on how the animal uses it. Net energy for maintenance (NEM) is the energy needed to keep the animal alive and warm. Net energy for gain (NEG) is the energy available for weight gain. Net energy for lactation (NEL) is the energy available for milk production.

Net energy values are expressed in megacalories per pound or per kilogram of dry matter. A megacalorie is 1,000 calories, the same unit used in human nutrition labels but multiplied by 1,000.

For beef cattle, the most useful energy values are TDN and the net energy pair NEM and NEG. A ration that meets the animal's TDN requirement will usually meet its net energy requirements as well. The net energy values become more important when you are fine-tuning rations for growing or finishing cattle.

For dairy cattle, NEL is the standard energy measure. Dairy rations are balanced to provide a specific amount of NEL based on milk production and body condition. The NEL value of a forage is calculated from TDN or from fiber digestibility.

For horses, the standard energy measure is digestible energy (DE), expressed in megacalories per pound. Most horse feed analysis reports include DE. A mature horse at maintenance needs about 16 to 18 megacalories of DE per day. A lactating mare needs 30 to 35 megacalories per day.

How to Use Feed Analysis to Balance Rations

Ration balancing is the process of combining feeds to meet an animal's nutrient requirements. The goal is to provide the right amounts of energy, protein, fiber, minerals, and vitamins without wasting money on excess nutrients.

The first step is to determine the nutrient requirements of the animals you are feeding. Requirements vary by species, age, weight, stage of production, and environmental conditions. Your local extension office can provide requirement tables, or you can use a ration balancing software program.

The second step is to test all the feeds you plan to use. This includes forages, grains, byproducts, and supplements. Every feed has its own nutrient profile, and you cannot assume values from a book or from a neighbor's test.

The third step is to calculate how much of each feed to include in the ration. This is where the math can get complicated, especially with multiple feeds and multiple nutrient requirements. Many producers use a spreadsheet or a ration balancing program to do this. Your extension office may offer free ration balancing software.

A simple approach for a single forage and a single supplement is the Pearson square method. This method calculates how much of two feeds to mix to achieve a target nutrient level. It works for one nutrient at a time, so you usually need to run it for protein and energy separately.

For example, suppose you have grass hay that tests 8 percent crude protein and you want to feed a 12 percent protein ration to growing calves. You have a 20 percent protein supplement. The Pearson square works like this:

Write the target protein in the center of a square. Write the protein content of each feed in the corners. Subtract diagonally and take the absolute value. The resulting numbers are the parts of each feed.

Target: 12 Hay: 8 Supplement: 20

Hay: 20 minus 12 equals 8 parts Supplement: 12 minus 8 equals 4 parts

The mix should be 8 parts hay to 4 parts supplement, which simplifies to 2 parts hay and 1 part supplement. That means two-thirds of the ration dry matter should be hay and one-third should be supplement.

The Pearson square only balances one nutrient. After you calculate the mix, check the other nutrients to make sure they are adequate. You may need to adjust the mix or add minerals to meet all requirements.

For most producers, a simpler approach is to feed a base forage and add a commercial supplement according to the label. Commercial supplements are formulated to complement average forages, but they work best when you know your forage quality. A feed analysis lets you choose the right supplement and feed the right amount.

Common Mistakes in Feed Analysis Interpretation

Many producers make predictable mistakes when reading feed analysis reports. Avoiding these errors will save you money and prevent animal health problems.

The most common mistake is comparing as-fed and dry matter values without converting. When you compare your hay test to a book value or to a neighbor's test, make sure both are on the same moisture basis. Book values are usually on a dry matter basis. Lab reports often show both as-fed and dry matter values, and it is easy to grab the wrong column.

The second most common mistake is ignoring the moisture content. Hay that tests 12 percent moisture is different from hay that tests 20 percent moisture even if the nutrient values on a dry matter basis are the same. The wetter hay will weigh more per bale, but you will get less dry matter per pound. When you buy hay by the ton, moisture content directly affects how much actual feed you are getting.

The third mistake is relying on a single sample to represent a diverse lot of feed. If you have hay from different fields, cuttings, or storage conditions, test them separately. A composite sample from a mix of good and poor hay will give you an average that describes neither. You will not know which bales are good enough to feed to lactating cows and which should go to dry cows.

The fourth mistake is ignoring the fiber digestibility numbers. Many producers focus on protein and energy and skip the NDFD value. But fiber digestibility can vary by 10 to 15 percentage points between forages with the same NDF. Higher fiber digestibility means more energy and higher intake. If your lab offers NDFD, pay attention to it.

The fifth mistake is feeding to the average instead of the variation. Feed tests are averages of the sample you submitted, and individual bales can vary around that average. If you have a lot of hay that tests 10 percent protein plus or minus 2 percent, some bales will be 8 percent and some will be 12 percent. Feed the better bales to animals with higher requirements and the poorer bales to animals with lower requirements.

The sixth mistake is not testing new feed before feeding it. Many producers feed a new load of hay or a new batch of silage before the lab results come back. If the feed is dramatically different from what you expected, you can cause digestive upsets, milk fat depression, or poor weight gains. Wait for the test results or feed the new feed gradually while mixing it with the old feed.

The seventh mistake is using feed analysis to justify a purchase instead of to inform a decision. If you have already decided to buy a particular load of hay, you will find a way to make the test look acceptable. Instead, get the test results before you commit to the purchase and compare the price per unit of nutrient across different lots.

Decision Thresholds for Feed Quality

Feed analysis reports are only useful if you know what the numbers mean for your operation. The following thresholds provide general guidance for common livestock classes. These are starting points, not substitutes for a nutritionist's advice.

Beef Cows

A mature beef cow in mid-gestation needs a ration with at least 7 percent crude protein and 52 percent TDN on a dry matter basis. Most average-quality grass hay will meet these requirements. A lactating beef cow needs 10 to 12 percent protein and 55 to 60 percent TDN. If your hay tests below these levels, you need to supplement with protein or energy.

Hay with a relative feed value below 80 is generally poor quality and will limit intake. Hay with an RFV of 80 to 100 is fair and suitable for dry cows. Hay with an RFV of 100 to 120 is good and suitable for lactating cows. Hay with an RFV above 120 is excellent and can support growing calves or high-producing cows.

Dairy Cows

Lactating dairy cows have the highest nutrient requirements of any common livestock class. A cow producing 80 pounds of milk per day needs a ration with 17 to 18 percent protein and an NEL of 0.74 to 0.78 megacalories per pound of dry matter. Most forages cannot meet these requirements alone, so dairy rations include significant amounts of grain and protein supplements.

For dairy forages, ADF should be below 30 percent and NDF should be below 40 percent for lactating cow diets. Forage NDF should be at least 19 to 21 percent of the total diet dry matter to maintain rumen health and milk fat. If forage NDF is too low, cows will have acidosis and milk fat depression.

Dry cows have much lower requirements. A dry cow needs about 12 percent protein and an NEL of 0.58 to 0.62 megacalories per pound. Overconditioning dry cows is a common problem when they are fed high-quality forage free choice. Limit dry cow intake or feed lower-quality forage to prevent excessive body condition.

Sheep and Goats

Sheep and goats have similar nutrient requirements to cattle on a body weight basis, but they are more selective eaters. They can sort through hay and leave the stems, which means the actual nutrient intake can be higher than the lab test suggests. This sorting behavior also means they waste more feed.

A mature ewe or doe in mid-gestation needs about 10 percent protein and 55 percent TDN. A lactating ewe with twins needs 14 to 16 percent protein and 65 percent TDN. Growing lambs and kids need 14 to 16 percent protein for moderate growth.

Sheep and goats are more sensitive to copper toxicity than cattle. Most commercial cattle minerals contain added copper and should not be fed to sheep. Have your forage tested for copper and other trace minerals if you are concerned about mineral imbalances.

Horses

Horses have different digestive physiology than ruminants. They cannot digest fiber as efficiently, so they need higher-quality forage to meet their energy needs. A mature horse at maintenance needs about 10 percent protein and 16 to 18 megacalories of digestible energy per day.

Good-quality grass hay for horses has an RFV of 100 to 120. Legume hay like alfalfa has higher protein and calcium, which is good for growing horses and lactating mares but can be too rich for idle horses. A horse at maintenance can be fed grass hay with 10 to 12 percent protein. A growing weanling needs 14 to 16 percent protein.

Horses are more sensitive to mold and dust than ruminants. A feed analysis does not detect mold, dust, or other quality issues that affect palatability and respiratory health. Always inspect hay visually and smell it before feeding, even if the lab test looks good.

Monitoring and Recordkeeping

Feed analysis is not a one-time event. It is an ongoing part of your management system. Keeping good records lets you track trends, make better buying decisions, and document your feeding program for audits or sales.

Keep a feed analysis file for every lot of feed you produce or purchase. Include the lab report, the submission form, and notes about the field, harvest date, storage method, and any observations about the feed. This file becomes your history of feed quality on your operation.

Record the price you paid for each lot of feed and calculate the cost per pound of protein and per megacalorie of energy. This lets you compare the true value of different feeds. A cheaper feed that is lower in nutrients may actually cost more per unit of nutrient.

Test every new lot of feed before you start feeding it. If you buy hay from multiple sources, test each source separately. If you harvest multiple cuttings, test each cutting. If you store hay differently, such as inside versus outside, test each storage method.

Retest stored feed periodically. Hay and silage change over time. Silage continues to ferment and can lose dry matter and energy during storage. Hay can lose quality if it is stored outside and exposed to moisture. A test at harvest time may not describe the feed six months later.

Monitor animal performance alongside your feed tests. Track body condition scores, weight gains, milk production, and reproductive performance. If animals are not performing as expected, your feed test may not reflect what animals are actually eating. Sorting, waste, and selective consumption can all cause a gap between the lab report and the animal.

Work with your veterinarian or extension agent to investigate problems. If animals lose condition despite a ration that appears balanced, there may be an underlying health issue, a feed mixing error, or a palatability problem. A feed analysis is one tool in the diagnostic toolbox, not the only tool.

When to Call a Veterinarian or Extension Agent

A feed analysis report can help you prevent problems, but it cannot diagnose disease. Call your veterinarian if animals show signs of nutritional deficiency or toxicity even when the feed test looks acceptable.

Signs of protein deficiency include poor growth, weight loss, rough hair coat, reduced milk production, and poor reproductive performance. Signs of energy deficiency include thin body condition, weakness, and reduced cold tolerance. Signs of mineral deficiency include poor bone development, weak calves, and reproductive problems.

Acute signs that require immediate veterinary attention include difficulty breathing, tremors, staggering, recumbency, and sudden death. These can indicate nitrate poisoning, urea toxicity, mold toxicity, or other acute feed-related problems. If multiple animals are affected at the same time, call your veterinarian immediately.

Your extension agent can help you interpret feed analysis reports and balance rations. Extension agents and specialists have training in animal nutrition and access to ration balancing software. They can also help you sample feed correctly and choose the right lab tests.

If you suspect a feed-related problem and you have fed the suspect feed to animals, save a sample of the feed and the lab report. This documentation is important for diagnosis and may be needed if you have a legal claim against a feed supplier.

Frequently Asked Questions

How often should I test my hay?

Test every lot of hay that comes from a different field, cutting, or harvest date. A lot means hay that is uniform in origin and storage. If you buy hay, test each load before feeding it. If you grow your own hay, test each cutting. Retest stored hay if it has been in storage for more than six months or if it shows signs of spoilage.

What is the difference between RFV and RFQ?

Relative feed value (RFV) is an index calculated from ADF and NDF. It predicts digestible dry matter and dry matter intake. Relative forage quality (RFQ) is a newer index that also uses fiber digestibility. RFQ is more accurate for grasses and warm-season forages. Use RFQ when it is available, especially for grass hay.

Can I feed hay without a feed analysis?

You can feed hay without a test, but you are guessing at the nutrient content. Visual appearance and smell do not reliably predict protein, energy, or mineral content. The cost of a feed test is small compared to the cost of overfeeding supplement or underfeeding animals. Most producers find that testing pays for itself in the first load of hay they buy or sell.

How do I take a good hay sample?

Use a hay probe or core sampler to take cores from the ends of at least 10 to 20 bales from the same lot. Combine the cores in a clean bucket, mix them, and fill a one-quart resealable bag. Label the bag and send it to the lab with the submission form. Do not grab flakes from the outside of bales because the outer layer is weathered and does not represent the whole bale.

What does crude protein really mean?

Crude protein is calculated by measuring nitrogen and multiplying by 6.25. It includes both true protein and non-protein nitrogen. For most forages, it is a reasonable estimate of usable protein for ruminants. For feeds with high non-protein nitrogen, like silage or feeds containing urea, it overestimates true protein.

Why is dry matter important?

Dry matter is the portion of the feed that is not water. It is the basis for all ration calculations. If you balance rations on an as-fed basis, you will make errors because feeds have different moisture contents. Always convert nutrient values to a dry matter basis before comparing feeds or calculating rations.

What nitrate level is dangerous?

Nitrate levels below 1,000 ppm are safe. Levels of 1,000 to 2,500 ppm are safe for non-pregnant animals but should be limited for pregnant animals. Levels above 2,500 ppm are dangerous and require dilution with other feeds. Levels above 5,000 ppm are toxic and can be fatal. Test for nitrates if your forage was drought stressed or heavily fertilized.

How do I know if my feed analysis is accurate?

Use a reputable lab that participates in proficiency testing programs. Most commercial feed testing labs and university labs meet this standard. If a result looks unusual, ask the lab to rerun the sample or send a duplicate sample to a second lab. NIRS results can occasionally be wrong for unusual feeds, so wet chemistry confirmation is available from most labs.

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References

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