# Dairy Cow Feed Storage and Silage Management ## Key Takeaways - Optimal silage fermentation requires harvesting corn silage at 30-35% dry matter and grass/legume silage at 35-45% dry matter to balance nutrient preservation with fermentation efficiency and minimize effluent losses. - Achieving a packing density of 700-800 lbs of dry matter per cubic yard is critical for excluding oxygen, preventing aerobic spoilage, and promoting lactic acid fermentation, with packing tractor weight being a key operational metric. - A daily feed-out rate of 6-12 inches in warm weather and 4-6 inches in cool weather is essential to minimize aerobic deterioration and heating of the silage face, indicated by a temperature rise of more than 10°F above ambient. - Routine feed testing, including dry matter, crude protein, NDF, ADF, starch, and pH, is vital for accurate ration balancing, with mycotoxin screening (especially for aflatoxin above 20 ppb) being a critical food safety measure. - Spoilage prevention hinges on minimizing oxygen infiltration through proper sealing, prompt repair of cover damage, and maintaining a clean, vertical feed face, as yeasts and molds proliferate in aerobic conditions. - Visible mold, strong butyric acid odors, or internal silage temperatures exceeding 120°F necessitate professional consultation due to potential mycotoxin contamination, reduced feed quality, and increased health risks for dairy cows. --- This article provides dairy farmers with practical guidance on silage making, bunker management, feed out practices, spoilage prevention, and feed testing. The content is based on established animal nutrition principles and published research. Proper feed storage and silage management directly affect feed quality, cow health, milk production, and farm profitability. The information here supports informed management decisions and helps identify when professional veterinary or nutritional advice is needed. ## At a Glance: Silage Management Decision Guide The table below summarizes key management areas, common practices, and indicators for monitoring success or identifying problems. | Management Area | Recommended Practice | Key Observation or Record | Escalation Criterion | |-----------------|----------------------|---------------------------|----------------------| | Harvest timing | Chop at 30-35% dry matter for corn silage, 35-45% for grass silage | Dry matter test results, chop length, kernel processing | Dry matter outside target range for two consecutive loads | | Packing density | Pack in layers 6-8 inches thick, achieve 700-800 lbs dry matter per cubic yard | Packing tractor weight, layer thickness, density probe readings | Density below 700 lbs DM per cubic yard at multiple points | | Feed out rate | Remove 6-12 inches per day from the face in warm weather, 4-6 inches in cool weather | Face temperature, visible mold, daily removal depth | Face temperature rise above ambient by 10°F or visible mold extending more than 2 inches into the face | | Feed testing | Test each new silo or bunker, then monthly during storage | Dry matter, crude protein, NDF, ADF, starch, pH, mold count | Aflatoxin detection above 20 ppb or any positive mycotoxin screen in feed | ## Silage Making Principles for Dairy Rations Silage is fermented, high-moisture forage stored under anaerobic conditions. The goal is to preserve as much of the original crop nutrients as possible while producing a palatable, stable feed. The [fermentation process](/knowledge/molecular-biology/fermentation-process) relies on lactic acid bacteria converting sugars into acids that lower pH and inhibit spoilage organisms. Successful silage making requires attention to crop maturity, moisture content, chop length, packing, and sealing. The [Merck Veterinary Manual](https://www.merckvetmanual.com/management-and-nutrition) provides foundational information on feed management and nutrition for livestock, including principles of forage preservation. For dairy cows, silage quality directly influences dry matter intake, rumen health, and milk component yields. Poorly fermented silage can reduce intake by 10-20% and increase the risk of metabolic disorders such as ruminal acidosis or displaced abomasum. Crop maturity at harvest is the first critical decision. Corn silage should be harvested when the kernel milk line is at one-half to two-thirds of the way down the kernel, corresponding to 30-35% dry matter. Grass and legume silages should be cut at early flowering to early bloom stage for optimal fiber digestibility. Harvesting too early produces wet silage with poor fermentation and high effluent losses. Harvesting too late results in low digestibility and reduced energy content. Chop length affects packing density and rumen function. For corn silage, a theoretical length of cut of 3/4 inch with kernel processing is standard. For haylage, a cut of 1/2 to 3/4 inch is typical. Shorter chop improves packing but can reduce effective fiber for rumen health. Longer chop may increase sorting at the feed bunk. ## Bunker and Drive-Over Pile Management Bunker silos and drive-over piles are common storage structures on dairy farms. Proper management of these structures determines feed quality throughout the storage period. The [USDA Natural Resources Conservation Service](https://www.nrcs.usda.gov/) provides technical guidance on agricultural waste management and feed storage structures, including recommendations for site selection, drainage, and runoff control. ### Site Preparation and Drainage The storage area should be on well-drained ground with a slight slope away from the structure to prevent water accumulation. A concrete floor is preferred to minimize soil contamination and provide a clean surface for packing equipment. If a concrete floor is not feasible, a compacted clay or gravel base can be used, but the risk of soil inclusion in feed increases. Drainage ditches or tile lines should divert surface water away from the silage mass. ### Filling and Packing Fill the bunker or pile as quickly as possible, ideally within 2-3 days for a single harvest. Delays between loads allow oxygen to penetrate the silage mass, promoting yeast and mold growth. Spread each load in thin layers, 6-8 inches deep, and pack continuously with a heavy tractor. Packing weight should be at least 800 pounds of tractor weight per ton of silage delivered per hour. For example, a 20-ton-per-hour harvest rate requires a packing tractor weighing at least 16,000 pounds. Density is the most important factor in silage preservation. Higher density excludes oxygen, limits heating, and improves fermentation. Target a packing density of at least 700 pounds of dry matter per cubic yard. Use a density probe or core sampler to verify density at multiple points across the pile face. Low density areas, especially along the sides and top, are prone to spoilage. ### Sealing and Covering Cover the silage immediately after filling with oxygen-barrier plastic sheeting. Use at least two layers: a clear, thin oxygen-barrier film next to the silage and a thicker black-and-white polyethylene cover on top. Weight the cover with tires, sandbags, or gravel tubes placed close together to minimize air movement under the plastic. Inspect the cover weekly for tears, holes, or animal damage. Repair any damage within 24 hours to prevent oxygen infiltration. The [Food and Agriculture Organization of the United Nations](https://www.fao.org/animal-production/en) provides resources on animal feed production and preservation, including silage management practices for different climates and farm scales. In hot or humid environments, additional attention to sealing and cover maintenance is required because higher temperatures accelerate spoilage. ## Feed Out Practices and Face Management How silage is removed from storage affects feed quality and cow intake. The goal is to remove a clean, uniform face that minimizes oxygen exposure to the remaining silage mass. ### Face Removal Rate Remove at least 6-12 inches from the entire face each day during warm weather and 4-6 inches during cool weather. This rate ensures that silage is fed before significant heating or spoilage occurs. In summer, a removal rate of 12 inches per day may be necessary to keep the face cool. In winter, 4-6 inches per day is often sufficient. Use a defacer, silage rake, or skid-steer loader to shave the face vertically from top to bottom. Do not dig into the pile or bunker from the bottom, as this can cause the face to collapse and create air pockets. A smooth, vertical face minimizes surface area exposed to oxygen. ### Temperature Monitoring Measure the temperature of the silage face at multiple points using a probe thermometer. A temperature rise of more than 10°F above ambient air temperature indicates active heating from yeast or mold growth. Heating reduces dry matter and energy content and can produce compounds that reduce palatability. If face temperature exceeds ambient by 15°F or more, increase the removal rate and consider feeding the affected silage to lower-producing animals or cull cows. ### Spoilage Removal Discard visibly moldy, discolored, or slimy silage before feeding. Do not feed silage with a strong musty, fermented, or putrid odor. Spoiled silage may contain mycotoxins that pose health risks to cows and can transfer into milk. The [USDA National Agricultural Library](https://www.nal.usda.gov/animal-health-and-welfare) provides information on animal health and welfare, including feed safety considerations. ## Spoilage Prevention and Mycotoxin Risks Spoilage in silage is primarily caused by yeasts, molds, and aerobic bacteria that become active when oxygen enters the silage mass. Preventing oxygen infiltration is the most effective spoilage control strategy. ### Common Spoilage Patterns Surface spoilage occurs on the top and sides of bunkers and piles where the cover is damaged or poorly sealed. This layer, typically 6-12 inches deep, should be removed and discarded before feeding. Heating in the silage face indicates ongoing aerobic deterioration. Hot spots can extend several feet into the silage mass if removal rates are too slow. Mold growth on silage is a concern because some molds produce mycotoxins. A review titled "Mycotoxicoses in dairy cattle: A review" published in the Asian Journal of Animal and Veterinary Advances (2015) discusses the impact of mycotoxins on dairy cattle health. Mycotoxins such as aflatoxin, deoxynivalenol (DON), and zearalenone can reduce feed intake, impair immune function, and decrease milk production. Aflatoxin M1 can appear in milk within 12-24 hours of contaminated feed consumption. A study titled "Detection of Aflatoxigenic Fungi in Dairy Cattle Feed: Findings From Urban Districts of Tigray, Ethiopia" published in [Veterinary Medicine](/blog/careers/veterinary-medicine-careers-from-clinical-practice-to-public-health) and Science (2025) identified aflatoxigenic fungi in dairy cattle feed samples. Another study, "Quantitative Analysis of Total Aflatoxins in Dairy Cattle Feed Using a Competitive [Lateral Flow Immunoassay](/knowledge/diagnostics/serology-immunology/lateral-flow-immunoassay-principles-design-and-applications): A Regional Study in Tigray, Ethiopia" published in Veterinary Medicine and Science (2026), reported measurable aflatoxin levels in feed. These findings underscore the importance of routine mycotoxin testing in dairy feed. The review "A Review of the Impact of Mycotoxins on Dairy Cattle Health: Challenges for [Food Safety](/knowledge/bacteria/livestock-bacteria/cooking-chicken-bacteria-prevention) and Dairy Production in Sub-Saharan Africa" published in Toxins (2020) highlights the food safety risks associated with mycotoxin contamination in dairy production systems. A study titled "Examination of covariance and correlation in aflatoxin levels between feeds and dairy cattle milk in Northern Greece" published in the Journal of the Hellenic Veterinary Medical Society (2025) found a correlation between aflatoxin levels in feed and milk, reinforcing the need for feed monitoring. ### Mycotoxin Testing Test silage and other feed components for mycotoxins at least twice per year, or whenever spoilage is observed. Use a commercial feed testing laboratory that offers mycotoxin panels. Collect representative samples from multiple locations in the silage mass. For aflatoxin, the FDA action level for dairy feed is 20 parts per billion (ppb). If aflatoxin is detected at any level, consult a [veterinary nutritionist](/blog/careers/becoming-a-veterinary-nutritionist-education-certification-and-practice) or feed safety specialist to assess risk and determine appropriate action. ### Additives and Preservatives Silage inoculants containing lactic acid bacteria can improve fermentation and reduce spoilage. Propionic acid-based preservatives can inhibit yeast and mold growth, particularly in silage that will be fed out slowly. However, additives cannot compensate for poor harvest timing, inadequate packing, or damaged covers. The most effective spoilage prevention strategy is proper management throughout the silage making and feed out process. ## Feed Testing and Quality Monitoring Regular feed testing provides the data needed to balance rations accurately and monitor silage quality over time. The [Merck Veterinary Manual](https://www.merckvetmanual.com/management-and-nutrition) emphasizes the importance of feed analysis for formulating dairy rations. ### Sampling Protocol Collect silage samples from the feed face just before feeding. Use a core sampler or grab samples from at least 10-15 locations across the face. Combine samples in a clean bucket, mix thoroughly, and place a subsample in a sealed plastic bag. Label the bag with the date, silo or bunker identification, and crop type. Ship or deliver samples to the laboratory within 24 hours, or freeze them if a delay is unavoidable. ### Key Analyses Standard feed analysis for dairy silage should include: - Dry matter (DM) - Crude protein (CP) - Neutral detergent fiber (NDF) - Acid detergent fiber (ADF) - Starch (for corn silage) - pH - Ash - Calcium, phosphorus, magnesium, potassium For corn silage, also request kernel processing score and starch digestibility. For haylage, request NDF digestibility (NDFD) at 30 or 48 hours. ### Interpreting Results Compare test results to target values for your herd and production stage. Dry matter should be consistent within a silo or bunker. Large variation in DM between samples indicates uneven fermentation or moisture migration. Low CP may indicate over-mature forage or nitrogen loss during fermentation. High NDF and ADF values suggest lower digestibility and energy content. pH is a measure of fermentation quality. Well-fermented silage typically has a pH of 3.8-4.2 for corn silage and 4.0-4.5 for haylage. Higher pH values may indicate poor fermentation or butyric acid production, which reduces palatability. ### Record Keeping Maintain a feed testing log that includes sample date, silo or bunker identification, crop type, harvest date, and all analytical results. Record any observations of spoilage, heating, or mold at the time of sampling. This log helps track changes in feed quality over time and supports ration adjustments. ## Ration Balancing and Feed Out Records Accurate feed testing data is essential for ration balancing. Rations formulated without current feed analysis may be deficient or excessive in nutrients, leading to reduced milk production, weight loss, or metabolic disorders. ### Using Feed Test Data Work with a dairy nutritionist to formulate rations based on the most recent feed test results. Update rations whenever a new silo or bunker is opened, or when feed test results change by more than 5% for DM, CP, or NDF. For herds with multiple silage sources, blend silages to achieve consistent nutrient content in the total mixed ration (TMR). ### Feed Out Records Record the amount of silage removed from storage each day. This can be done by weighing feed wagons or by measuring the volume removed and calculating weight based on density. Compare actual feed out to expected feed out based on herd size and ration formulation. Discrepancies may indicate feed waste, inaccurate ration formulation, or changes in cow intake. Track the date each silo or bunker is opened and the date it is emptied. This information helps plan harvest schedules and ensures that silage is fed within its optimal storage life. Most silage maintains good quality for 6-12 months if properly stored, but quality declines gradually after opening. ## Common Failure Patterns in Silage Management Recognizing common failure patterns helps dairy farmers correct problems before they affect cow performance. ### Poor Fermentation Signs of poor fermentation include high pH (above 4.5), strong butyric acid odor, and dark brown or green color. Causes include harvesting at too high moisture content, insufficient packing, or slow filling. Poor fermentation reduces palatability and intake. Affected silage may need to be blended with well-fermented silage or fed to lower-producing animals. ### Heating in the Bunker Heating during storage indicates oxygen infiltration. Common causes include inadequate packing density, damaged covers, or slow feed out rates. Heating reduces dry matter and energy content. In severe cases, spontaneous combustion can occur, though this is rare. If internal temperature exceeds 120°F, consult a feed safety specialist. ### Mold Development Mold on the silage face or in the feed bunk indicates oxygen exposure. Surface mold is common on the top layer of bunkers and should be removed before feeding. If mold extends more than 2-3 inches into the silage face, increase the removal rate and inspect the cover for damage. Moldy silage should be tested for mycotoxins before feeding. ### Inconsistent Dry Matter Variation in dry matter within a silo or bunker suggests uneven moisture at harvest, poor mixing during filling, or moisture migration during storage. Inconsistent DM makes ration balancing difficult and can cause rumen upset. If DM varies by more than 5% between samples, consider blending silage from different areas of the bunker to achieve more uniform feed. ## Welfare and Safety Considerations Feed storage and silage management have implications for animal welfare, worker safety, and food safety. ### Animal Welfare Cows fed spoiled or moldy silage may experience reduced feed intake, digestive upset, and increased disease risk. Mycotoxin exposure can impair immune function and increase susceptibility to infections. The [USDA National Agricultural Library](https://www.nal.usda.gov/animal-health-and-welfare) provides resources on animal health and welfare, including the importance of feed quality. Providing clean, palatable, nutritionally balanced feed is a fundamental aspect of dairy cow welfare. ### Worker Safety Bunker silos and drive-over piles present physical hazards. Workers can be injured by falling silage, equipment rollovers, or entrapment in flowing silage. Never enter a bunker silo or pile while filling or removing feed. Use equipment with rollover protection structures (ROPS) and seat belts. Ensure that all workers are trained in safe silage handling procedures. Silage gases, particularly nitrogen dioxide, can accumulate in enclosed silos during the first few weeks after filling. Nitrogen dioxide is toxic and can cause severe lung injury or death. Never enter a silo without proper ventilation and gas monitoring equipment. If you suspect gas accumulation, ventilate the silo for at least 30 minutes before entering. ### Food Safety Mycotoxin contamination in feed can transfer to milk, posing a risk to consumers. The review "A Review of the Impact of Mycotoxins on Dairy Cattle Health: Challenges for Food Safety and Dairy Production in Sub-Saharan Africa" published in Toxins (2020) discusses the food safety implications of mycotoxin contamination in dairy systems. Routine feed testing and proper storage practices are essential for producing safe milk. The study "Examination of covariance and correlation in aflatoxin levels between feeds and dairy cattle milk in Northern Greece" published in the Journal of the Hellenic Veterinary Medical Society (2025) found a positive correlation between aflatoxin levels in feed and milk. This reinforces the need for vigilant feed monitoring and rapid response when contamination is detected. ## Professional Escalation Criteria Dairy farmers should seek professional advice from a veterinarian, dairy nutritionist, or feed safety specialist in the following situations: - Aflatoxin detected in feed at any level above 20 ppb - Any positive mycotoxin screen in feed, even at low levels - Silage pH above 4.5 with strong butyric acid odor - Internal silage temperature exceeding 120°F - Unexplained drop in milk production or feed intake lasting more than 3 days - Multiple cows showing signs of digestive upset, such as diarrhea, bloat, or off-feed - Positive milk aflatoxin test result - Worker injury or near-miss incident involving silage handling equipment ## Frequently Asked Questions ### What is the ideal dry matter content for corn silage? Corn silage should be harvested at 30-35% dry matter. This moisture level supports proper fermentation and packing while minimizing effluent losses. Harvesting below 30% DM increases the risk of clostridial fermentation and nutrient losses through seepage. Harvesting above 35% DM makes packing difficult and increases the risk of heating and mold growth. ### How often should I test my silage for mycotoxins? Test silage for mycotoxins at least twice per year, ideally when a new silo or bunker is opened and again midway through the storage period. Test more frequently if you observe visible mold, heating, or if cows show signs of reduced intake or health problems. Always test silage that will be fed to high-producing cows or cows in early lactation. ### What is the correct removal rate from a silage bunker face? Remove 6-12 inches from the entire face each day during warm weather and 4-6 inches during cool weather. The removal rate should be adjusted based on face temperature. If the face temperature is more than 10°F above ambient, increase the removal rate. A smooth, vertical face minimizes oxygen exposure. ### Can I feed silage that has visible mold? Do not feed silage with visible mold to dairy cows. Moldy silage may contain mycotoxins that can reduce feed intake, impair health, and transfer into milk. Remove and discard all visibly moldy silage before feeding. If mold is present on the silage face, test the remaining silage for mycotoxins before feeding. ### How do I prevent heating in my silage bunker? Prevent heating by achieving high packing density (at least 700 lbs DM per cubic yard), sealing the bunker immediately after filling with oxygen-barrier plastic, and removing silage at a rate that keeps the face cool. Inspect the cover weekly for damage and repair any tears promptly. Heating is a sign of oxygen infiltration and requires immediate corrective action. ### What records should I keep for silage management? Maintain records of harvest date, crop type, dry matter at harvest, packing density measurements, feed test results, mycotoxin test results, date each silo or bunker is opened and emptied, daily feed out amounts, and any observations of spoilage, heating, or mold. These records support ration balancing, quality tracking, and troubleshooting. ### When should I call a veterinarian about feed-related issues? Call a veterinarian if multiple cows show signs of digestive upset such as diarrhea, bloat, off-feed, or reduced milk production lasting more than 3 days. Also call if you suspect mycotoxin exposure based on feed test results or if milk aflatoxin testing is positive. A veterinarian can assess herd health, recommend diagnostic testing, and coordinate with a nutritionist to adjust the ration. ### How does silage quality affect milk production? Silage quality directly affects dry matter intake, rumen health, and nutrient availability. Poorly fermented silage with high pH, low digestibility, or mycotoxin contamination can reduce feed intake by 10-20% and decrease milk production. High-quality silage with good fermentation, adequate fiber digestibility, and no mycotoxins supports optimal intake and milk component yields. ## Related Farming Guides - [Dairy Cow Cooling System Management](/knowledge/animal-farming/dairy-cattle/dairy-cow-cooling-system-management) - [Beef Cattle Backgrounding Management](/knowledge/animal-farming/beef-cattle/beef-cattle-backgrounding-management) - [Beef Cattle Manure Management](/knowledge/animal-farming/beef-cattle/beef-cattle-manure-management) - [Beef Cattle Mud Management](/knowledge/animal-farming/beef-cattle/beef-cattle-mud-management) - [Beef Cattle Quarantine Management](/knowledge/animal-farming/beef-cattle/beef-cattle-quarantine-management) ## Related Clinical & Scientific Guides * [Evaluating Feed Additives for Dairy Cow Performance](/knowledge/animal-farming/dairy-cattle/evaluating-feed-additives-for-dairy-cow-performance) * [Dairy Barn Fire Safety: Design and Prevention Measures](/knowledge/animal-farming/dairy-cattle/dairy-barn-fire-safety-design-prevention) * [Dairy Cow Pregnancy Loss Records and Review](/knowledge/animal-farming/dairy-cattle/dairy-cow-pregnancy-loss-records-and-review) ## References and Further Reading - [www.nrcs.usda.gov](https://www.nrcs.usda.gov/) - [www.merckvetmanual.com](https://www.merckvetmanual.com/management-and-nutrition) - [FAO Animal Production and Health](https://www.fao.org/animal-production/en). Food and Agriculture Organization of the United Nations. - [Animal Health and Welfare](https://www.nal.usda.gov/animal-health-and-welfare). USDA National Agricultural Library. - [Feed resources, feeding system and feed balance of dairy cattle in Chencha District, Southern Ethiopia.](https://pubmed.ncbi.nlm.nih.gov/39324870). Veterinary medicine and science, 2024. - [Detection of Aflatoxigenic Fungi in Dairy Cattle Feed: Findings From Urban Districts of Tigray, Ethiopia.](https://pubmed.ncbi.nlm.nih.gov/40323976). Veterinary medicine and science, 2025. - [A Review of the Impact of Mycotoxins on Dairy Cattle Health: Challenges for Food Safety and Dairy Production in Sub-Saharan Africa.](https://pubmed.ncbi.nlm.nih.gov/32252249). Toxins, 2020. - [Greenhouse gas emissions from the enteric fermentation and manure storage of dairy and beef cattle in China during 1961-2010.](https://pubmed.ncbi.nlm.nih.gov/25262083). Environmental research, 2014. - [Quantitative Analysis of Total Aflatoxins in Dairy Cattle Feed Using a Competitive Lateral Flow Immunoassay: A Regional Study in Tigray, Ethiopia.](https://pubmed.ncbi.nlm.nih.gov/41330863). Veterinary medicine and science, 2026. - [Review: Sugar beets as a substitute for grain for lactating dairy cattle.](https://pubmed.ncbi.nlm.nih.gov/28286650). Journal of animal science and biotechnology, 2017. - [Mycotoxicoses in dairy cattle: A review](https://doi.org/10.3923/ajava.2015.752.760). Asian Journal of Animal and Veterinary Advances, 2015. - [Feeding management for dairy cattle in smallholder farming systems of semi-arid tropical Kenya](https://api.elsevier.com/content/abstract/scopus_id/79955944649). Livestock Research for Rural Development, 2011. - [Examination of covariance and correlation in aflatoxin levels between feeds and dairy cattle milk in Northern Greece](https://doi.org/10.12681/jhvms.39644). Journal of the Hellenic Veterinary Medical Society, 2025. - [Biofermentation of aquatic plants: Potential novel feed ingredients for dairy cattle production](https://doi.org/10.1016/j.scitotenv.2024.175955). Science of the Total Environment, 2024. > This article is educational and is not a substitute for veterinary diagnosis, treatment, public-health guidance, or regulatory reporting.