Dairy Cow Feed Testing and Forage Analysis for Ration Balancing

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

Key Takeaways

• Regular forage testing, utilizing a probe for representative sampling and submitting to a certified laboratory for wet chemistry analysis of critical minerals and NIRS for routine screening, is paramount. This practice mitigates significant economic losses from inaccurate ration balancing, which can lead to reduced milk production or metabolic disorders.
• A comprehensive nutrient package for analysis should include dry matter, crude protein (with fractions), ADF, NDF, NDF digestibility (30-hour), starch, sugar, fat, ash, and essential macro and trace minerals (Ca, P, Mg, K, S). These parameters are critical for formulating rations that meet the complex digestive needs of ruminants.
• Forages, particularly haylage and silage, must be tested upon harvest stabilization and retested every 4-6 weeks during feeding due to ongoing fermentation and dry matter fluctuations. This ensures the ration remains balanced as nutrient profiles evolve, preventing under or overfeeding.
• Ration balancing requires a systematic approach, starting with determining the cow's specific nutrient requirements based on production and physiological stage, then balancing for energy (Net Energy for Lactation), protein (rumen degradable and undegradable fractions), minerals, and crucially, physical effective fiber to maintain rumen health and prevent acidosis.
• Monitoring key physiological indicators such as dry matter intake (target 3.5-4.0% body weight), milk production and composition (especially milk fat depression as an acidosis indicator), manure consistency (score 3 is normal), and body condition score (3.0-3.5 for lactating cows) is essential to verify ration efficacy and identify potential health issues linked to diet.
• Accurate record-keeping of all forage tests, ration changes, and production responses, reviewed monthly, is vital for identifying trends, optimizing future feeding strategies, and informing decisions regarding harvest and storage management.

Feed costs represent the largest single expense on most dairy operations, often accounting for 50 to 60 percent of total production costs. Yet many dairy farmers balance rations using book values for forage nutrient content, assuming that this year's hay crop matches last year's averages. That assumption can cost you thousands of dollars in lost milk production, wasted feed, or both. This guide explains how to sample feeds correctly, interpret laboratory reports, and use those results to build a ration that supports production goals without wasting money on overfeeding or risking health problems from underfeeding. It is written for dairy producers, herd managers, and farm employees who want to take control of their feeding program through regular feed testing and forage analysis.

At a Glance

• Test every new batch of forage before feeding it. Do not rely on book values or last year's test results.
• Sample forages correctly using a probe. Grab samples from bales or piles give unreliable results.
• Submit samples to a certified forage testing laboratory. Ask for wet chemistry analysis for critical minerals and use NIRS for routine screening.
• Request a complete nutrient package including dry matter, crude protein, ADF, NDF, NDF digestibility, starch, sugar, fat, ash, calcium, phosphorus, magnesium, potassium, sulfur, and trace minerals.
• Test haylage and silage within a few days of harvest or immediately after the fermentation period stabilizes. Retest whenever you open a new silo or move to a different cutting.
• Use forage test results to balance rations for energy, protein, minerals, and physical effective fiber. Work with a nutritionist if you do not have training in ration balancing.
• Monitor dry matter intake, milk production, milk components, manure consistency, body condition score, and rumen health indicators to verify that the ration is working.
• Keep detailed records of every test result, ration change, and production response. Review these records at least monthly.
• Call your veterinarian or extension agent if you see signs of ruminal acidosis, displaced abomasum, milk fat depression, or other health problems that may be linked to the ration.

Why Feed Testing Matters for Dairy Cows

Dairy cows are ruminants with a complex digestive system that depends on a stable population of bacteria, protozoa, and fungi in the rumen. These microorganisms break down fiber and starch into volatile fatty acids that the cow uses for energy, and they produce microbial protein that supplies a large portion of the cow's amino acid needs. The rumen microbiome is sensitive to changes in diet composition, particle size, and feeding schedule. When the ration changes suddenly or when nutrient levels are out of balance, rumen function suffers and cow health declines.

Forage quality varies enormously from field to field, cutting to cutting, and even within a single storage structure. Weather at harvest, stage of maturity, soil fertility, plant species, and storage method all influence the nutrient content of the final feed. Alfalfa cut at early bloom may contain 20 percent crude protein, while the same field cut at full bloom may drop to 15 percent. Corn silage harvested at the right moisture and maturity can provide 70 percent total digestible nutrients, but if it is harvested too dry or too wet, energy content falls and fermentation quality suffers.

When you feed a ration based on outdated or incorrect forage values, you have two possible problems. If the actual forage is lower in energy or protein than your assumed values, cows will not meet their nutrient requirements. Milk production drops, body condition is lost, and reproductive performance suffers. If the actual forage is higher in energy or protein than your assumed values, cows may consume more energy than they need. This can lead to fat cows, displaced abomasums, ketosis, and other metabolic disorders.

Feed testing removes the guesswork. It tells you exactly what is in the feed so you can formulate a ration that meets the cow's requirements without excess or deficiency. Regular testing also helps you track changes in forage quality over time, identify problems with harvest or storage, and make informed decisions about purchasing supplemental feeds.

Understanding the Nutrient Analysis Report

Forage laboratory reports can look intimidating with their columns of abbreviations and numbers, but each value tells you something important about the feed. Learn to read the report so you can discuss it with your nutritionist and make informed decisions.

Dry Matter

Dry matter is the percentage of the feed that is not water. It is the foundation for all other nutrient calculations. When you balance a ration, you work on a dry matter basis so that you are comparing feeds fairly. A cow eats a certain amount of dry matter each day, and that dry matter must supply all the nutrients she needs.

Fresh pasture may be 20 to 25 percent dry matter, meaning it is 75 to 80 percent water. Haylage typically runs 35 to 55 percent dry matter depending on how long it wilted before chopping. Corn silage is usually 30 to 40 percent dry matter. Dry hay is 85 to 90 percent dry matter.

The dry matter content of a feed affects how much the cow can physically eat. High-moisture feeds fill the rumen with water, limiting intake. Very dry feeds may also limit intake because they are dusty or unpalatable. The dry matter value also determines how much of each feed to put in the mixer wagon. If you formulate a ration on a dry matter basis but feed on an as-fed basis, you must convert using the dry matter percentage.

Crude Protein

Crude protein is an estimate of the total protein in the feed. It is calculated by measuring the nitrogen content and multiplying by 6.25, because protein averages about 16 percent nitrogen. Crude protein includes both true protein and non-protein nitrogen such as urea or nitrates.

For dairy rations, you also need to know how the protein is fractionated. The laboratory report may show soluble protein, degradable protein, and undegradable protein. Rumen degradable protein is broken down by rumen microbes into ammonia and used to build microbial protein. Rumen undegradable protein, also called bypass protein, escapes rumen degradation and is digested in the small intestine. High-producing cows need a balance of both fractions to meet their amino acid requirements.

Acid Detergent Fiber and Neutral Detergent Fiber

Acid detergent fiber and neutral detergent fiber are measures of the plant cell wall components. Neutral detergent fiber includes cellulose, hemicellulose, and lignin. It represents the total fiber fraction of the feed. Acid detergent fiber includes cellulose and lignin and is closely related to digestibility. As plants mature, both fractions increase and digestibility decreases.

Neutral detergent fiber is important for several reasons. It stimulates chewing and saliva production, which buffers the rumen. It provides a physical mat in the rumen that promotes normal rumination and prevents displaced abomasum. It also limits feed intake because it fills the rumen. Cows typically eat about 1.1 to 1.2 percent of their body weight as neutral detergent fiber from forage. If the forage neutral detergent fiber is too high, cows cannot eat enough energy to support high production.

Acid detergent fiber is used to estimate energy content. As acid detergent fiber increases, energy decreases. The laboratory uses acid detergent fiber in equations to predict total digestible nutrients and net energy for lactation.

Neutral Detergent Fiber Digestibility

Neutral detergent fiber digestibility measures how much of the fiber the cow can actually digest. This value is increasingly important in forage evaluation because it explains why two forages with the same neutral detergent fiber content can perform very differently in the cow.

Neutral detergent fiber digestibility is measured at 24, 30, or 48 hours of incubation. The 30-hour value is commonly reported. Higher values mean the cow can extract more energy from the fiber. Brown midrib corn silage varieties have higher neutral detergent fiber digestibility than conventional varieties. Legumes generally have higher fiber digestibility than grasses at the same neutral detergent fiber content.

Forage with high neutral detergent fiber digestibility supports higher dry matter intake because the fiber clears from the rumen faster. This is especially important for high-producing cows that need maximum energy intake.

Starch and Sugar

Starch is the primary energy storage compound in corn silage and other grain forages. Sugar is found in grasses, legumes, and some silages. Both provide rapidly fermentable energy for rumen microbes.

Starch content in corn silage typically ranges from 25 to 40 percent on a dry matter basis. Higher starch usually means more energy, but it also increases the risk of ruminal acidosis if the ration is not balanced with adequate effective fiber. The laboratory may report starch as total starch or as rumen degradable starch. Rumen degradable starch is the fraction that is fermented in the rumen, and it is more useful for ration balancing.

Fat

Fat is a concentrated energy source. Forages are low in fat, usually 2 to 4 percent of dry matter. Supplemental fats are often added to dairy rations to increase energy density. The laboratory report shows either crude fat or ether extract. Some labs also report fatty acid profiles, which can be useful for managing milk fat synthesis.

Ash and Minerals

Ash is the total mineral content of the feed. High ash values may indicate soil contamination, which can occur when forage is harvested too close to the ground or when silage is contaminated with dirt. Ash provides no energy or protein, so high ash dilutes the nutrient content of the feed.

The mineral analysis shows calcium, phosphorus, magnesium, potassium, sulfur, sodium, and trace minerals. These values are essential for balancing the mineral portion of the ration. Potassium interacts with other minerals and affects the dietary cation anion difference, which is important for dry cow rations. Sulfur is needed for amino acid synthesis but can interfere with copper and selenium absorption if present in excess.

Relative Feed Value and Relative Forage Quality

Relative feed value and relative forage quality are index numbers that combine neutral detergent fiber and acid detergent fiber to rank forages for quality. They are useful for comparing lots of hay or for marketing hay, but they are not sufficient for ration balancing. Two forages with the same relative feed value can have very different protein, starch, or mineral contents.

Relative feed value is calculated from acid detergent fiber and neutral detergent fiber. Relative forage quality uses the same fiber values but also incorporates neutral detergent fiber digestibility. Both indices assume that intake is limited by neutral detergent fiber and that digestibility is related to acid detergent fiber. These assumptions are not always accurate, so use the indices for comparison but balance the ration on the actual nutrient values.

How to Sample Forages Correctly

The accuracy of your feed test depends entirely on the quality of your sample. A poor sample gives misleading results no matter how good the laboratory is. Take the time to collect a representative sample and handle it properly.

Sampling Hay

Use a hay probe attached to a drill to collect cores from bales. The probe should be at least 18 inches long and 0.5 to 0.75 inches in diameter. Insert the probe into the end of the bale, perpendicular to the surface, and push it all the way through to the other side. Collect cores from at least 10 to 20 bales per lot, sampling bales from different locations in the stack or field.

A hay lot is a group of bales from the same field, cutting, and harvest date that were stored under the same conditions. Do not mix bales from different cuttings or fields in one sample. If you have 100 bales from one field and 50 from another, sample them separately.

For square bales, probe through the end of the bale from the twine side. For round bales, probe from the side or the end. Avoid sampling the outer layer of weathered hay because it does not represent the whole bale. Combine all the cores in a clean plastic bucket and mix thoroughly. Place about one pound of the composite sample in a labeled plastic bag and seal it.

Sampling Haylage and Silage

Sampling haylage and silage is more challenging because the feed is fermented and may contain pockets of spoilage. The best time to sample is during harvest or when you are filling the silo, because you can collect samples from the chopper or wagon as the forage is being harvested. Take samples from several loads and combine them into a composite sample.

If you are sampling from a silo or bunker after storage, collect samples from the face of the pile. Remove the loose, spoiled outer layer first. Then take small handfuls from the top, middle, and bottom of the exposed face, working from the side of the pile toward the center. Collect at least 12 to 15 subsamples and combine them.

For silo bags or wrapped bales, sample after the bag or wrap is opened. Take cores from several points along the length of the bag using a silage probe. Avoid the spoiled ends of the bag.

Sampling Total Mixed Rations

Sampling the total mixed ration tells you what the cow is actually eating, not just what you formulated. This is a valuable check on mixer accuracy and feed sorting. Collect samples from multiple points in the feed bunk immediately after feeding, before the cows have had a chance to sort. Combine the subsamples and mix well.

Forage particle size analysis is also important for total mixed ration evaluation. Use a particle separator box with three or four screens to check the distribution of long particles, medium particles, and fines. The ideal distribution depends on the ration and the feeding system, but a common target is 2 to 8 percent on the top screen, 30 to 50 percent on the second screen, and 30 to 40 percent on the bottom pan.

Sample Handling and Shipping

Place the sample in a clean plastic bag and squeeze out as much air as possible. Seal the bag and label it with your name, farm name, sample identification, forage type, and date. Keep the sample cool or frozen until you ship it to the laboratory. Use an insulated shipping container with ice packs during warm weather.

Ship the sample to the laboratory as soon as possible. Most laboratories can provide results within a few days of receiving the sample. Do not let samples sit in a hot mailbox or truck for days before shipping.

Choosing a Laboratory and Test Package

Forage testing laboratories vary in their methods, quality control, and turnaround time. Choose a laboratory that participates in the National Forage Testing Association certification program or a similar proficiency testing program. Certified laboratories have demonstrated that their results are accurate and repeatable.

The two main analytical methods are near-infrared reflectance spectroscopy and wet chemistry. Near-infrared reflectance spectroscopy is fast and inexpensive. The instrument scans the sample with near-infrared light and compares the spectrum to a calibration developed from wet chemistry analysis of many samples. It works well for routine screening of protein and fiber.

Wet chemistry analysis uses actual chemical reactions to measure nutrients. It is more accurate for minerals and for unusual feeds that may not be well represented in the near-infrared reflectance spectroscopy calibration. Ask for wet chemistry analysis when you need accurate mineral values, when you are testing unusual feeds, or when near-infrared reflectance spectroscopy results seem inconsistent with the feed.

A complete forage test package should include dry matter, crude protein, soluble protein, acid detergent fiber, neutral detergent fiber, neutral detergent fiber digestibility at 30 hours, starch, sugar, fat, ash, calcium, phosphorus, magnesium, potassium, sulfur, and the major trace minerals. Some laboratories also offer estimates of total digestible nutrients, net energy for lactation, and relative forage quality.

The cost of a standard forage test is typically 25 to 60 dollars per sample depending on the laboratory and the test package. This is a small investment compared to the potential savings from more accurate ration balancing. If you feed 100 tons of haylage per year and the test results allow you to reduce purchased protein by 10 percent, you will save far more than the cost of testing.

How Often to Test Forages

Test every new batch of forage before you feed it. This means testing each cutting of hay, each silo or bag of haylage, and each field of corn silage. Do not assume that the second cutting of alfalfa is similar to the first cutting. Weather, soil moisture, and plant maturity can change the nutrient content dramatically.

For hay, test when the bales are dry and ready to store. This gives you the information before you start feeding. For haylage and corn silage, test shortly after harvest or as soon as the fermentation is complete. The fermentation process changes the nutrient profile, so testing fresh forage immediately after chopping gives different results than testing after fermentation.

For silage stored in bunkers, piles, or bags, retest when you open the structure and start feeding. Samples taken during harvest reflect the average of the whole crop, but the feed at the top, bottom, and ends of the pile may be different. Spoiled or moldy areas should be removed and not fed, and they should not be included in your sample.

During the feeding period, retest silage every four to six weeks. Silage continues to ferment and change during storage. Dry matter can change as water moves through the pile. Nutrient values at the beginning of the feeding period may not match values at the end.

Using Forage Test Results to Balance the Ration

Ration balancing is a complex process that requires training and experience. If you do not work with a nutritionist, consider hiring one. A nutritionist can help you interpret test results, formulate a balanced ration, and adjust the ration as forages change. The cost of professional nutrition services is usually recovered through improved milk production and reduced feed costs.

If you balance rations yourself, follow these steps to use your forage test results effectively.

Step 1: Determine the Cow's Nutrient Requirements

The cow's nutrient requirements depend on body weight, milk production, milk fat percentage, stage of lactation, pregnancy status, and environmental conditions. The National Research Council nutrient requirements for dairy cattle provide the standard values used in ration balancing. Most ration balancing software includes these requirements in its database.

A cow producing 80 pounds of milk per day with 3.8 percent milk fat needs more energy and protein than a cow producing 50 pounds per day. Fresh cows in early lactation have high nutrient demands but limited dry matter intake, so the ration must be nutrient dense. Late lactation cows can maintain production on a lower nutrient density because they eat more dry matter per pound of milk produced.

Step 2: Set Up the Ration

Start with the forages you have available. Determine how much of each forage you can feed based on storage, availability, and the cow's ability to consume dry matter. Forage should provide 50 to 70 percent of the total dry matter in the ration for most lactating cows.

The forage portion of the ration supplies the physical effective fiber needed for normal rumen function. The non-forage portion supplies additional energy, protein, and minerals. The goal is to balance the ration so that the cow meets all her nutrient requirements without excesses or deficiencies.

Step 3: Balance for Energy

Energy is often the first limiting nutrient in dairy rations. Use the net energy for lactation value from the forage test to calculate how much energy the forage provides. If the forage does not supply enough energy, add concentrates such as corn grain, barley, or byproduct feeds. If the forage supplies more energy than needed, reduce the concentrate level.

The energy density of the total ration is expressed as net energy for lactation in megacalories per pound of dry matter. A typical lactating cow ration contains 0.70 to 0.78 megacalories per pound of dry matter. High-producing cows need the higher end of this range.

Step 4: Balance for Protein

Use the crude protein value and the protein fractions to calculate how much protein the forage provides. Compare this to the cow's requirement for metabolizable protein. If the forage is low in protein, add protein supplements such as soybean meal, canola meal, or distillers grains. If the forage is high in protein, you may be able to reduce purchased protein supplements.

The protein concentration of the total ration should be 16 to 18 percent crude protein on a dry matter basis for most lactating cows. The rumen degradable protein should supply 60 to 65 percent of the total protein, with the remainder as rumen undegradable protein.

Step 5: Balance for Minerals

Use the mineral values from the forage test to calculate how much calcium, phosphorus, magnesium, potassium, sulfur, and trace minerals the forage provides. Add mineral supplements to meet the cow's requirements. Pay special attention to calcium and phosphorus ratios, magnesium for grass tetany prevention, and potassium for dry cow rations.

The calcium to phosphorus ratio should be between 1.5 to 1 and 2 to 1 for lactating cows. Magnesium should be 0.25 to 0.35 percent of the ration dry matter. Potassium should be 1.0 to 1.5 percent for lactating cows but lower for dry cows to prevent milk fever.

Step 6: Check Physical Effective Fiber

Physical effective fiber is the fiber that stimulates chewing and rumination. It is related to the particle size of the forage and the neutral detergent fiber content. Cows need at least 22 to 25 percent physical effective neutral detergent fiber in the ration to maintain normal rumen function.

Forage particle size is important. Hay and haylage should have particles at least 1.5 to 2 inches long to promote chewing. Corn silage should have some particles longer than 0.5 inches. If the ration is too finely ground, cows will not chew enough and rumen pH will drop.

Common Mistakes in Feed Testing and Ration Balancing

Many dairy farmers make the same mistakes when they test feeds and balance rations. Recognizing these mistakes can help you avoid them.

Sampling Errors

The most common mistake is taking a poor sample. A handful of hay from the top of a bale does not represent the whole bale. A sample from the center of a silo face does not represent the spoiled edges. Always use a probe, take multiple cores, and combine them into a composite sample.

Another sampling error is testing the wrong thing. If you want to know what the cow is eating, sample the total mixed ration, not just the individual ingredients. If you want to know the quality of the forage you are storing, sample during harvest or from multiple locations in the storage structure.

Infrequent Testing

Some farmers test forages once a year or only when they suspect a problem. This is not enough. Forage quality changes with each cutting, each field, and each storage structure. Test every new batch and retest stored feeds periodically.

Ignoring Dry Matter Changes

Silage dry matter changes during storage. Water may drain from the bottom of a bunker, leaving the remaining feed drier. Rain may add water to uncovered piles. If you do not adjust the ration for dry matter changes, you will overfeed or underfeed the cow.

Check silage dry matter at least monthly. Use a microwave oven or a Koster tester for a quick on-farm measurement, or send a sample to the laboratory. Adjust the as-fed amounts in the ration to maintain the same dry matter intake.

Using Book Values Instead of Test Results

Book values are averages from many samples. They may be close to your forage, or they may be far off. The only way to know what is in your forage is to test it. Do not rely on book values when you have the ability to test.

Forgetting to Test Water

Water is a nutrient that is often overlooked. Poor quality water can reduce feed intake and milk production. Test your water source at least once a year for total dissolved solids, sulfates, nitrates, iron, and bacteria. If cows drink less water, they eat less feed and produce less milk.

Not Adjusting the Ration When Forages Change

When you open a new silo or start feeding a new cutting of hay, the cows need time to adjust. Change the ration gradually over several days to avoid digestive upset. The rumen microbes need time to adapt to new feeds and new nutrient levels.

Monitoring the Response to Ration Changes

Feed testing and ration balancing are not one-time events. They are ongoing processes that require monitoring and adjustment. Watch these indicators to see if the ration is working.

Dry Matter Intake

Dry matter intake is the most important indicator of ration success. Cows should eat 3.5 to 4.0 percent of their body weight as dry matter, depending on stage of lactation and production level. A cow weighing 1,400 pounds should eat 49 to 56 pounds of dry matter per day.

Monitor feed intake by weighing the feed offered and the feed refused. The refusal rate should be 3 to 5 percent for a total mixed ration. If cows are cleaning the bunk completely, they may not be getting enough feed. If they are leaving more than 5 percent, they may be sorting the ration or the ration may be unpalatable.

Milk Production and Composition

Milk production responds quickly to changes in energy and protein intake. If milk production drops after a ration change, the new ration may not meet the cow's nutrient requirements. If milk production increases, the ration may be supporting higher production.

Milk fat percentage is a sensitive indicator of rumen health. Milk fat depression often indicates ruminal acidosis or insufficient effective fiber. Milk protein percentage reflects energy intake. When energy is adequate, milk protein is usually 3.0 to 3.2 percent. When energy is deficient, milk protein drops.

Manure Consistency

Manure consistency tells you about digestion and rumen health. Normal dairy cow manure is a pile that is moderately firm with visible fiber particles. Manure that is very loose or watery may indicate acidosis, excessive protein, or rapid ration changes. Manure that is very firm or dry may indicate dehydration or insufficient fiber.

Use a manure scoring system to evaluate the consistency. Score 1 is very watery, score 5 is very firm, and score 3 is normal. Look for undigested grain in the manure, which indicates poor starch digestion or sorting.

Body Condition Score

Body condition score reflects the cow's energy balance over time. Score cows on a 1 to 5 scale, with 1 being very thin and 5 being very fat. Lactating cows should maintain a body condition score of 3.0 to 3.5. Cows that lose condition are using body fat to support milk production, which is normal in early lactation but should not continue for more than 60 to 90 days.

Rumen Health Indicators

Watch for signs of ruminal acidosis, including reduced feed intake, low milk fat, diarrhea, laminitis, and displaced abomasum. These problems often occur when the ration contains too much starch or not enough effective fiber. If you see these signs, check the ration for starch content and particle size.

Rumenocentesis can measure rumen pH directly, but it is invasive and not practical for routine monitoring. Instead, monitor rumen health through milk fat percentage, manure consistency, and cow behavior. Cows should spend 8 to 10 hours per day ruminating, usually in 15 to 20 minute bouts.

When to Call a Veterinarian or Extension Agent

Most ration adjustments can be handled by you and your nutritionist. However, some situations require professional help. Call your veterinarian if you see signs of metabolic disease, such as ketosis, milk fever, or displaced abomasum. These conditions require diagnosis and treatment, not just ration changes.

Call your veterinarian if multiple cows are off feed, if milk production drops suddenly, or if you see signs of digestive upset that do not respond to ration adjustments. These could indicate a feed quality problem such as mold, mycotoxins, or spoiled silage. Your veterinarian can help you diagnose the problem and recommend treatment.

Call your extension agent if you need help interpreting forage test results, if you want to learn more about ration balancing, or if you are considering major changes to your feeding program. Extension agents can provide educational materials, workshops, and referrals to specialists.

Record Keeping for Feed Testing and Ration Management

Good records help you track changes over time and make better decisions. Keep a notebook or spreadsheet with the following information for each forage sample:

• Sample identification and date
• Field, cutting, and harvest date
• Forage type and variety
• Storage method and location
• Laboratory and test method
• Complete nutrient analysis results
• Ration changes made based on the results
• Dry matter intake, milk production, and milk composition at the time of the test
• Any health problems or unusual observations

Review your records at least monthly. Look for trends in forage quality, milk production, and cow health. Use the records to plan next year's harvest, storage, and feeding strategies.

Frequently Asked Questions

How often should I test my dairy cow feed?

Test every new batch of forage before feeding it, including each cutting of hay, each silo or bag of haylage, and each field of corn silage. Retest stored silage every four to six weeks during the feeding period because dry matter and nutrient content change during storage. For dry hay, one test per lot is usually sufficient because the nutrient content is stable once the hay is baled and stored properly.

What is the difference between NIRS and wet chemistry forage analysis?

Near-infrared reflectance spectroscopy uses light to estimate nutrient content by comparing the sample to a calibration database. It is fast, inexpensive, and accurate for routine screening of protein and fiber. Wet chemistry uses actual chemical reactions to measure nutrients and is more accurate for minerals and unusual feeds. Use wet chemistry when you need accurate mineral values, when testing feeds that may not be in the near-infrared reflectance spectroscopy calibration, or when near-infrared reflectance spectroscopy results seem inconsistent with the feed.

How do I take a representative hay sample?

Use a hay probe attached to a drill. The probe should be at least 18 inches long and 0.5 to 0.75 inches in diameter. Insert the probe into the end of the bale and push it all the way through. Collect cores from at least 10 to 20 bales per lot, sampling bales from different locations in the stack. Combine all cores in a clean bucket, mix thoroughly, and place about one pound in a labeled plastic bag.

What nutrients should I test for in my forage?

Request a complete package that includes dry matter, crude protein, soluble protein, acid detergent fiber, neutral detergent fiber, neutral detergent fiber digestibility at 30 hours, starch, sugar, fat, ash, calcium, phosphorus, magnesium, potassium, sulfur, and trace minerals. These values are essential for balancing energy, protein, and minerals in the ration.

Can I balance a ration using only the relative feed value or relative forage quality?

No. Relative feed value and relative forage quality are index numbers that rank forages for quality, but they do not provide the detailed nutrient information needed for ration balancing. They combine only fiber values and do not account for protein, starch, minerals, or fiber digestibility. Use the actual nutrient values from the test report to balance the ration.

Why does my silage test show different dry matter than what I put in the silo?

Silage dry matter changes during storage. Water may drain from the bottom of a bunker, leaving the remaining feed drier. Fermentation produces water and carbon dioxide, which can change the dry matter. Rain may add water to uncovered piles. The outer layers of the pile may be wetter or drier than the center. Retest silage periodically and adjust the as-fed amounts in the ration to maintain consistent dry matter intake.

What should I do if my cows are not eating enough of the total mixed ration?

First check the ration for palatability. Spoiled or moldy feed, high levels of certain byproducts, or poor mixing can reduce intake. Check the particle size distribution using a particle separator box. If the ration is too fine, cows may not be getting enough effective fiber. If the ration is too coarse, cows may sort out the grain and leave the forage. Check the dry matter of the ration, because very wet or very dry rations limit intake. If the problem persists, work with your nutritionist to adjust the ration.

How do I know if my cows have ruminal acidosis?

Signs of ruminal acidosis include reduced feed intake, low milk fat percentage, diarrhea, laminitis, and displaced abomasum. Cows may also show signs of discomfort such as kicking at their belly or grinding their teeth. If you suspect acidosis, check the ration for starch content and effective fiber. Work with your veterinarian and nutritionist to diagnose the problem and adjust the ration.

Related Farming Guides

This section will be populated with links to related farming guides on dairy cattle nutrition, forage management, and herd health topics.

Related Clinical & Scientific Guides

• Evaluating Feed Additives for Dairy Cow Performance
• Dairy Barn Fire Safety: Design and Prevention Measures
• Dairy Cow Pregnancy Loss Records and Review

References

• National Mastitis Council: https://www.nmconline.org/
• USDA APHIS Dairy Cattle Health: https://www.aphis.usda.gov/livestock-poultry-disease/cattle
• FAO Dairy Production and Products: https://www.fao.org/dairy-production-products/en/
• 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.