Total Mixed Ration (TMR) for Dairy: Mixing and Feeding Management

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

Key Takeaways

• A Total Mixed Ration (TMR) consolidates forages, grains, protein, minerals, vitamins, and additives into a single, uniform feed to ensure consistent nutrient intake with every bite, mitigating digestive upsets and production losses associated with feed sorting.
• Effective TMR management hinges on precise mixer calibration, accurate dry matter calculations adjusted for forage moisture fluctuations, and a consistent loading order to protect particle size integrity and achieve uniform blending.
• Optimal feeding practices include frequent feed push-ups (3-5% refusals), regular bunk cleaning, and consistent feeding schedules to maximize dry matter intake and support rumen health.
• Monitoring key performance indicators such as dry matter intake, milk production and components, manure consistency, and cow behavior is crucial for early detection of ration-related issues and metabolic disorders.
• Common TMR feeding errors include overmixing, overloading the mixer, incorrect ingredient loading order, neglecting forage moisture adjustments, and inconsistent feeding times, all of which negatively impact feed efficiency and herd health.

Feeding a total mixed ration is one of the most effective ways to improve milk production, herd health, and feed efficiency on a dairy operation. This guide covers the full process of TMR dairy feeding, from ration design principles to mixer calibration, feeding management, and common mistakes that cost producers money. It is written for dairy farmers, herd managers, and farm employees who want to improve their feeding program with practical, actionable steps.

At a Glance

• A TMR combines forage, grains, protein supplements, minerals, vitamins, and additives into a single uniform mixture that provides every bite with a balanced diet.
• The goal is to keep the ration consistent from the start of the feeding to the end, so every cow eats the same balanced diet.
• Proper mixer management includes correct loading order, adequate mixing time, regular calibration, and routine maintenance.
• Dry matter matters more than as-fed weight. Always calculate rations on a dry matter basis and adjust for forage moisture changes.
• Push up feed frequently, aim for 3 to 5 percent refusals, and clean bunks regularly to encourage maximum intake.
• Monitor cow behavior, rumen fill, manure consistency, milk production, and component levels to catch feeding problems early.
• The most common TMR feeding mistakes are overmixing, overloading, incorrect loading order, ignoring forage moisture changes, and inconsistent feeding times.
• Call your veterinarian or extension agent when you see multiple cows off feed, a sudden drop in milk, or signs of acidosis or other metabolic disorders.

What Is a Total Mixed Ration and Why Use It

A total mixed ration is a method of feeding dairy cattle where all feed ingredients are blended together into one complete feed. Instead of feeding forages, grains, and protein supplements separately, you mix everything into a single ration that cows eat throughout the day. The idea is simple: every mouthful a cow takes contains the same balance of nutrients.

The TMR approach was developed to address a fundamental problem in dairy nutrition. When cows are fed ingredients separately, they often sort through the feed and eat the most palatable parts first. A cow might eat all the grain at the start of the meal and leave the forage for later. This creates wide swings in nutrient intake throughout the day, which can lead to digestive upsets, reduced milk production, and health problems like acidosis.

TMR feeding solves this problem by making it physically difficult for cows to sort their feed. The ingredients are mixed into a uniform blend, and the particle size distribution is designed to encourage cows to eat all components together. This stabilizes rumen conditions, improves fiber digestion, and supports higher feed intake.

The benefits of TMR dairy feeding are well documented in commercial practice. Herds on TMR typically show more consistent milk production, better milk fat tests, fewer digestive disorders, and improved feed efficiency compared to component feeding systems. The TMR also allows you to include lower-cost byproduct feeds that might not be palatable enough to feed separately. Byproducts like wet brewers grains, soybean hulls, and cottonseed can be incorporated into the mix where they are consumed readily.

A TMR system also saves labor. You feed once or twice per day instead of managing multiple feed deliveries to different groups. This frees up time for other herd management tasks. The initial investment in a mixer wagon and related equipment is significant, but most operations find the return comes through improved milk production and feed efficiency.

TMR feeding is not just for large dairies. Smaller herds can benefit from a TMR system too, though the economics depend on your scale and existing infrastructure. Many operations with 50 to 100 cows use TMR successfully, often with a smaller vertical mixer or a stationary mixer that loads into a feed cart.

Understanding the Components of a Dairy TMR Recipe

Before you can mix a good TMR, you need to understand what goes into the ration. A typical dairy TMR recipe contains several categories of ingredients, each serving a specific purpose in the cow's diet.

Forages are the foundation of the ration. Corn silage, alfalfa haylage, grass silage, and dry hays provide the fiber that dairy cows need for proper rumen function. Forages supply energy, protein, and fiber, and they stimulate chewing and saliva production. The quality of your forages has the biggest impact on ration performance. Poor quality forage cannot be fully corrected by adding more grain or supplements.

Grains and energy feeds supply starch and other carbohydrates that drive milk production. Corn grain is the most common energy feed in dairy rations. Other options include barley, wheat, molasses, and byproduct feeds like citrus pulp or beet pulp. These ingredients increase the energy density of the ration, allowing cows to produce more milk than they could from forage alone.

Protein supplements provide the amino acids cows need for milk protein synthesis and tissue maintenance. Soybean meal is the standard protein supplement, but other options include canola meal, distillers grains, cottonseed meal, and commercial protein blends. The protein content and degradability of these feeds vary, and your ration should balance both rumen-degradable protein and rumen-undegradable protein.

Minerals and vitamins fill the gaps in the ration. A complete mineral premix typically includes calcium, phosphorus, magnesium, potassium, sulfur, sodium, and trace minerals like zinc, copper, manganese, and selenium. Vitamins A, D, and E are also included. These are usually added at a small rate, often 1 to 2 pounds per cow per day, but they are critical for health, reproduction, and immune function.

Feed additives are optional ingredients that serve specific purposes. Buffers like sodium bicarbonate help stabilize rumen pH in high-grain rations. Yeast cultures support fiber digestion and feed intake. Ionophores like monensin improve feed efficiency. Other additives might include bypass fats, rumen-protected amino acids, or feed flavorings. Each additive should be evaluated for its return on investment in your specific operation.

Water is not usually listed as a TMR ingredient, but it is the most important nutrient. Cows need free access to clean, fresh water at all times. A cow producing 80 pounds of milk will drink 35 to 45 gallons of water per day. Inadequate water intake will limit dry matter intake and milk production no matter how well your TMR is formulated.

Designing the Dairy TMR Recipe

The ration formulation itself should be done by a professional nutritionist. This is not a task to handle on your own unless you have advanced training in dairy nutrition. A nutritionist will balance the ration based on your forages, your production goals, and your herd's needs. However, you need to understand the basics so you can manage the program effectively.

The starting point for any TMR recipe is knowing what your cows need. Dry matter intake is the foundation. A lactating cow typically eats 3.5 to 4.5 percent of her body weight in dry matter per day. A 1,400 pound cow producing 80 pounds of milk might eat 55 to 65 pounds of dry matter daily. Higher producing cows eat more, and first lactation heifers eat less than mature cows.

The ration is formulated to meet the energy, protein, fiber, mineral, and vitamin needs of the target cow. Your nutritionist will use your forage test results to determine what the forages contribute and then add other ingredients to balance the diet. Forage testing should be done at least monthly for fermented feeds like silage and haylage, because their nutrient content changes over time.

Particle size is a critical part of the TMR recipe that is often overlooked. Cows need adequate effective fiber to maintain rumen health. Effective fiber is the fiber that stimulates chewing and rumination. The Penn State Particle Separator is the standard tool for measuring TMR particle size. A properly mixed TMR should have about 2 to 8 percent of particles on the top screen, 30 to 50 percent on the second screen, 30 to 40 percent on the third screen, and no more than 20 percent in the bottom pan.

The goal is to provide enough long particles to support rumen function while keeping the ration mixed well enough to prevent sorting. If the ration has too many long particles, cows will sort out the grain. If it is too finely chopped, rumen health suffers and milk fat drops.

Your nutritionist will give you a target ration in dry matter pounds. You then convert that to as-fed pounds based on the moisture content of each ingredient. This is where many feeding mistakes happen, and it is covered in detail in the mixing section below.

TMR Mixer Options and Selection

The mixer wagon is the heart of a TMR feeding system. Choosing the right mixer for your operation depends on herd size, available tractor horsepower, feeding frequency, and budget. There are three main types of mixer wagons.

Vertical mixers are the most common choice for modern dairy operations. They have one or two vertical augers that chop and mix the feed. Vertical mixers handle long-stemmed hay well because the augers break it down during mixing. They are available in a wide range of sizes, from small units for 50 cow herds to large trailers for herds of 1,000 cows or more. Vertical mixers work well with a skid steer or loader for filling.

Horizontal mixers use one or two horizontal augers in the bottom of the mixing chamber. They are generally gentler on the feed than vertical mixers, which can be an advantage for preserving particle size. However, they require more pre-processing of hay and do not handle long-stemmed forage as well. Horizontal mixers are less common in new installations but are still found on many operations.

Truck-mounted mixers are self-propelled units that combine the mixer with a truck chassis. These are used on very large dairies where speed and efficiency are critical. They are expensive to purchase and maintain but can reduce labor costs significantly on operations feeding 1,000 cows or more.

Stationary mixers are fixed units that mix feed and discharge into a TMR feeder wagon or feed cart. These are an option for smaller operations or for farms that want to reduce the cost of a self-propelled unit. The stationary mixer is filled by a loader, and the mixed ration is discharged into carts that are pulled through the barn.

When selecting a mixer, consider the capacity you need. The mixer should be able to handle your largest batch size without being overloaded. A good rule is to fill the mixer to no more than 70 to 80 percent of its rated capacity. Overloading reduces mixing quality and can damage the machine. If you feed 60 cows at 60 pounds of as-fed feed per cow, you need to mix about 3,600 pounds per batch. A mixer rated for 5,000 to 6,000 pounds would be appropriate.

Also consider the power requirements. Vertical mixers with a single auger typically require 10 to 15 horsepower per 1,000 pounds of capacity. Twin auger mixers require a bit more. Your tractor must have enough power to operate the mixer at the recommended speed, especially when mixing dry hay or heavily baled forages.

Calibrating the TMR Mixer

Calibration is the process of verifying that the mixer is weighing ingredients accurately. An uncalibrated mixer will deliver a ration that does not match what your nutritionist formulated. This can lead to overfeeding expensive ingredients or underfeeding critical nutrients.

The scale system on your mixer should be checked at least monthly, and more often if you suspect problems. The procedure is straightforward. Park the mixer on level ground and zero the scale. Add a known weight of material, such as a pallet of feed that has been weighed on a certified scale. Compare the mixer scale reading to the known weight. The scale should be accurate within 1 to 2 percent.

If the scale is inaccurate, the load cells may need adjustment or replacement. This is a job for a qualified technician. Do not try to adjust load cells yourself unless you have the proper training and equipment. Inaccurate scales cost you money every day they are in use.

Also check the scale indicators and connections. Loose wires, corroded connectors, and damaged cables can cause erratic readings. Keep the scale area clean and free of feed buildup, which can affect weight readings.

Beyond the scale, you should calibrate your loading equipment. If you use a loader to fill the mixer, the bucket weights you use should be verified. Weigh a bucket of each ingredient and record the weights. These become your reference for loading. Recheck these weights whenever the moisture content of the feed changes significantly.

Loading Order for the TMR Mixer

The order in which you add ingredients to the mixer has a significant impact on the final mix quality. The goal is to protect the integrity of each ingredient while achieving a uniform blend. The correct loading order depends on your mixer type and the ingredients you are using.

A general loading order for a vertical mixer starts with the longest, most fibrous ingredients first. Long-stemmed hay or haylage should go in first so it gets the most mixing time to break down to the proper particle size. This is followed by other forages like corn silage or haylage. The forages should be mixed for a short period to establish a base for the rest of the ingredients.

After the forages are partially mixed, add the grain and protein concentrates. These smaller particles need less mixing time to incorporate. Add them in the middle of the mixing cycle so they are distributed throughout the forage base without being ground too fine.

Add liquid ingredients like molasses, liquid fats, or water last. Liquids added too early can coat the other ingredients and prevent proper mixing. Add them near the end of the cycle so they are distributed evenly without overmixing.

Minerals, vitamins, and additives should be added with the concentrates. If you use a premix, add it at the same time as the grains. This ensures it is distributed evenly through the ration.

For horizontal mixers, the loading order is similar but the mixing dynamics are different. Long hay should be processed before loading if possible, because horizontal mixers do not chop forage as effectively as vertical mixers. Some operations run hay through a bale processor before adding it to a horizontal mixer.

The key principle is to give the longest particles the most mixing time and the shortest particles the least. This protects the particle size distribution of the ration while achieving a uniform blend.

Mixing Time and Speed

Mixing time is one of the most critical variables in TMR management. Too little mixing leaves a nonuniform ration with clumps of individual ingredients. Too much mixing creates an overprocessed ration with particles that are too fine, which reduces effective fiber and can cause acidosis.

The ideal mixing time varies by mixer type, ingredient mix, and load size. Most vertical mixers require 3 to 7 minutes of mixing time after the last ingredient is added. Horizontal mixers typically require 4 to 8 minutes. These are general guidelines, and you should work with your nutritionist and equipment dealer to establish the right time for your specific setup.

A better approach is to use a visual and physical evaluation of the mix. Take samples of the TMR at different mixing times and evaluate them with the Penn State Particle Separator. You want a consistent particle size distribution and no visible clumps of individual ingredients. Once you find the mixing time that produces a good mix, standardize on that time and check periodically.

Mixer speed also matters. Running the mixer too fast creates excessive particle breakdown and increases wear on the machine. Running too slowly may not provide adequate mixing action. Most mixers have a recommended PTO speed, often 540 rpm. Operating at the recommended speed gives the best balance of mixing quality and equipment longevity.

Overmixing is a common problem on many dairies. Operators often mix longer than necessary to be safe, but this degrades the ration. Overmixed TMR has a mushy texture with reduced effective fiber. Cows eat it faster, which can lead to slug feeding and acidosis. The solution is to establish the correct mixing time and stick to it.

Also consider the order of operations. If you mix multiple batches per day, the mixing time for each batch should be consistent. Do not mix one batch for 5 minutes and the next for 10 minutes. Consistency is key to maintaining a uniform ration.

Adjusting for Forage Moisture

Forage moisture content changes constantly, and these changes affect your TMR recipe. Corn silage and haylage can vary by several percentage points in moisture from week to week, and even day to day. If you do not adjust your loading weights for these changes, the ration you deliver will not match the formulation.

The issue is that ration formulations are calculated on a dry matter basis. Your nutritionist specifies the pounds of dry matter from each ingredient. You then convert to as-fed pounds based on the moisture content. If the forage is wetter than expected, you need to feed more as-fed pounds to deliver the same dry matter. If it is drier, you feed fewer as-fed pounds.

For example, suppose your ration calls for 30 pounds of dry matter from corn silage. If the silage is 65 percent moisture, that is 35 percent dry matter. You need to feed 85.7 pounds of as-fed silage to deliver 30 pounds of dry matter. If the silage moisture drops to 60 percent, the dry matter is 40 percent, and you only need 75 pounds of as-fed silage.

This is why regular forage moisture testing is essential. At minimum, test the moisture of your fermented forages weekly. Many operations test every time they change silos or silage faces. A microwave moisture tester or a Koster tester can give you quick results on farm. Your nutritionist can also run moisture tests on samples you send to the lab.

When you get a new moisture reading, recalculate your loading weights. Your nutritionist can provide a spreadsheet or app that makes this calculation simple. The key is to make the adjustment promptly. Do not wait until the next ration formulation to adjust for moisture changes.

Also remember that moisture changes affect the total weight of the ration. If the silage is wetter, the total as-fed weight of the batch will be higher. Adjust your target batch weight accordingly so you do not overload the mixer or underfill it.

Managing the Silage Face and Forage Quality

The quality of the forage you put into the mixer is the foundation of the entire TMR program. Even the best mixer and the most careful loading cannot overcome poor forage quality. Managing your silage face properly preserves quality from harvest through feeding.

When removing silage from a bunker or pile, take a clean face. Remove at least 12 inches per day in cold weather and more in warm weather to keep the face fresh. A smooth, vertical face minimizes spoilage and keeps the silage from heating. Use a defacer or a loader to cut the face cleanly rather than tearing at it.

Discard any spoiled or moldy silage. Do not feed black, brown, or musty silage to cows. Spoiled feed can cause off flavors in milk, reduce intake, and introduce mycotoxins. It is better to lose a few pounds of spoiled feed than to compromise the entire ration.

The density of the silage affects your loading weights. Silage density varies with packing, moisture, and particle size. A loader bucket of silage may weigh more or less than expected depending on these factors. Check the actual weight of your loader buckets periodically and adjust your loading counts accordingly.

Forage quality changes as you move through a silo. The feed at the top and edges may be lower quality than the feed in the center. The nutrient content also changes as the silage ferments and stabilizes. Test the forage regularly and adjust the ration as the quality changes.

Hay quality is equally important. Test each cutting of hay and adjust the ration accordingly. Store hay under cover to protect it from weather damage. Discard any hay that is moldy, dusty, or otherwise spoiled.

Feeding Frequency and Timing

Cows are creatures of habit, and they thrive on a consistent feeding schedule. Feed delivery times should be consistent from day to day. Cows expect to be fed at the same time, and they will adjust their eating behavior accordingly. Inconsistent feeding times cause slug feeding and digestive upsets.

Most operations feed once or twice per day. Once daily feeding works well if the bunk space is adequate and the ration is stable. Twice daily feeding encourages more even intake throughout the day and can support higher dry matter intake in high producing herds. Some very high producing herds feed three times per day.

If you feed once daily, aim to deliver feed at a time when cows are motivated to eat, typically after milking. The feed should be delivered so that cows have access to fresh feed for 20 to 22 hours per day. This maximizes intake opportunity.

If you feed twice daily, space the feedings evenly, about 12 hours apart. This provides a steady supply of fresh feed and keeps cows coming to the bunk throughout the day. Some operations feed a larger portion in the morning and a smaller portion in the evening, but this is less common.

Regardless of feeding frequency, the key is consistency. Feed at the same times every day. If you must change the schedule, do it gradually over several days. Cows that are used to a routine will show reduced intake and production if the schedule changes abruptly.

Also consider the relationship between feeding and milking. Cows should have access to fresh feed when they return from the milking parlor. This encourages them to eat after the stress of milking and supports a consistent intake pattern. Some operations feed immediately after milking, while others feed slightly before or after. Work with your routine to find what works best for your cows.

Pushing Up Feed and Bunk Management

Pushing up feed is a simple task that has a big impact on intake. Cows prefer to eat from a full bunk, and they will not reach far to access feed. If the feed is pushed out of reach, intake drops. The goal is to keep feed within easy reach of the cows at all times.

Push up feed at least 2 to 4 times per day, and more often in hot weather or with high producing herds. Some operations push up feed every 2 to 3 hours. The task takes only a few minutes with a tractor or skid steer, and the return in intake and production is significant.

The frequency of pushing up depends on your bunk space and the number of cows. If cows have plenty of bunk space, they may not push feed out of reach as quickly. If bunk space is limited, feed will be pushed away faster and require more frequent attention.

Bunk management also involves monitoring refusals. The goal is to have 3 to 5 percent refusals at the next feeding. This means the cows are eating most of what you deliver but have a small amount left over. Refusals below 3 percent suggest cows may be limited in intake. Refusals above 5 percent indicate overfeeding, which wastes money.

Weigh the refusals regularly to track intake accurately. If you feed 60 pounds of as-fed TMR per cow and have 3 pounds of refusal, the actual intake is 57 pounds. This information helps your nutritionist adjust the ration and helps you manage feed costs.

Clean out the bunk regularly to remove spoiled or unpalatable feed. The frequency depends on the ration and the environment. In hot, humid weather, feed can spoil quickly and should be cleaned more often. Some operations clean bunks daily, while others clean every few days. The key is to remove any feed that is heating, molding, or becoming unpalatable.

Managing Refusals and Feed Shrink

Feed shrink is the difference between the feed you purchase and the feed your cows actually consume. Shrink occurs through spoilage, waste, theft by wildlife, and errors in weighing or mixing. High shrink rates are a major source of profit loss on dairy operations.

The first step in managing shrink is measuring it. Track the weight of feed delivered to the mixer, the weight of the TMR delivered to the cows, and the weight of refusals. The difference is shrink. A shrink rate of 5 to 10 percent is common, but rates above 10 percent indicate significant waste.

Silage shrink starts at harvest. Poor packing, inadequate sealing, and slow feedout all increase spoilage losses. Aim for a packing density of at least 15 to 18 pounds of dry matter per cubic foot. Seal the pile promptly and maintain the plastic cover to minimize oxygen infiltration. Feed out at a rate of at least 12 inches per day in warm weather to keep the face fresh.

Dry feed shrink comes from wind, spills, and pests. Store grains and concentrates in covered bins or buildings. Clean up spills promptly to avoid attracting rodents and birds. Keep the feed storage area tidy and free of debris.

In the mixer, shrink occurs through overfilling, which causes feed to spill over the sides. It also occurs through incomplete discharge. Make sure the mixer is emptied completely after each batch. Some feed may remain in the corners or around the augers.

Refusals are a form of shrink if they are not fed to another group. Many operations feed refusals to dry cows, heifers, or young stock. This recovers some of the value of the feed. However, refusals should not be fed to lactating cows, as they may contain spoiled or unpalatable feed.

Common TMR Feeding Mistakes

Many feeding problems on dairy operations come down to a handful of common mistakes. Understanding these mistakes can help you avoid them on your farm.

Overmixing is perhaps the most common mistake. Operators mix longer than necessary, which grinds the feed too fine and reduces effective fiber. The result is lower milk fat, increased acidosis risk, and reduced feed intake. The solution is to establish the correct mixing time and monitor particle size regularly.

Overloading the mixer is another frequent error. When the mixer is filled beyond its rated capacity, the feed does not mix properly. The result is a nonuniform ration with pockets of individual ingredients. Always fill the mixer to no more than 70 to 80 percent of its rated capacity.

Incorrect loading order is a third common mistake. Adding concentrates before forages or adding liquids too early can result in poor mixing. Follow the recommended loading order for your mixer and ingredients.

Ignoring forage moisture changes is a costly mistake. Feeding the same as-fed weights when forage moisture has changed means the cows get a different ration than formulated. This can lead to reduced production or digestive upsets. Test forage moisture regularly and adjust loading weights accordingly.

Inconsistent feeding times are another problem. Cows thrive on routine, and inconsistent feeding schedules disrupt eating behavior. Feed at the same times every day to maintain consistent intake.

Poor bunk management reduces intake. Not pushing up feed frequently enough, allowing feed to spoil, and failing to clean bunks all reduce intake and production. The bunk should be managed as carefully as the mixer.

Not monitoring particle size is a mistake that is easy to make but hard to see. Without regular particle size checks, you cannot know if the ration is mixing correctly. Use a Penn State Particle Separator at least weekly to verify the mix.

Feeding spoiled feed is a serious mistake that can cause health problems and reduce intake. Never feed moldy, heating, or spoiled feed to cows. Discard spoiled feed and correct the management practices that caused the spoilage.

Monitoring the TMR Program

A successful TMR program requires ongoing monitoring. You cannot simply formulate a ration, mix it, and expect everything to work without attention. Regular monitoring helps you catch problems early and make adjustments before they cost you production and profit.

Monitor dry matter intake closely. Track intake daily and look for trends. A sudden drop in intake often signals a problem with the ration, the feed, or the cows. A gradual decline may indicate a forage quality issue or a health problem in the herd.

Monitor milk production and composition. Milk yield, milk fat, and milk protein are sensitive indicators of ration performance. A drop in milk fat may indicate inadequate effective fiber or too much starch. A drop in milk protein may indicate inadequate energy or protein intake. Work with your nutritionist to interpret these changes and adjust the ration.

Monitor cow behavior and body condition. Cows should be calm, with good rumen fill and regular rumination. Check for cows that are off feed, lethargic, or showing signs of discomfort. Body condition should be stable or improving according to your herd goals. Cows that are losing condition are not getting enough energy.

Monitor manure consistency. Manure that is loose, foamy, or contains undigested feed particles may indicate digestive problems. Manure that is very firm may indicate inadequate intake or a ration that is too high in fiber. Normal dairy manure should form a flat patty, about 1 to 2 inches thick, with a smooth surface.

Monitor rumen fill and rumination. Cows should be ruminating 8 to 10 hours per day. You can observe rumination by watching cows at rest. A cow that is ruminating shows rhythmic jaw movements and regurgitates cuds. Low rumination time suggests inadequate effective fiber or a health problem.

Monitor feed sorting behavior. Cows that sort their feed are eating a different ration than the one you mixed. Sorting is a sign of particle size problems or a ration that is too palatable in some components. Watch for cows that push feed around or leave certain components uneaten.

Keep records of all these observations. A simple notebook or spreadsheet can track daily intake, milk production, refusals, and any problems you observe. These records help you identify trends and work with your nutritionist to make informed decisions.

TMR Particle Size Management

Particle size is one of the most important and most overlooked aspects of TMR management. The physical form of the ration affects rumen health, feed intake, milk fat, and cow comfort. Managing particle size requires regular measurement and adjustment.

The Penn State Particle Separator is the standard tool for measuring TMR particle size. This device has three screens and a bottom pan. The top screen has 19 millimeter openings, the second screen has 8 millimeter openings, and the third screen has 4 millimeter openings. You place a sample of TMR on the top screen, shake it in a specific pattern, and weigh the material on each screen.

The target distribution for a lactating cow TMR is approximately 2 to 8 percent on the top screen, 30 to 50 percent on the second screen, 30 to 40 percent on the third screen, and no more than 20 percent in the bottom pan. These targets ensure adequate effective fiber while allowing good mixing and intake.

If too much material is on the top screen, the ration has too many long particles. Cows will sort out the grain and concentrate, leaving the long forage. This reduces the energy intake of the cows and can cause acidosis. The solution is to mix longer or process the forage more before mixing.

If too much material is in the bottom pan, the ration is overprocessed. The particles are too fine, which reduces effective fiber and can cause milk fat depression and acidosis. The solution is to reduce mixing time or adjust the processing of the forage.

Check particle size at least weekly, and more often when you change forages or mixing procedures. Take samples from different parts of the bunk to get a representative picture. Also check the particle size of the TMR at the start and end of the feeding, because cows may sort the feed over time.

Remember that particle size targets are different for dry cows and heifers. Dry cow rations typically have more long particles to support rumen health and prevent displaced abomasum. Work with your nutritionist to establish the right targets for each group.

Ration Consistency and Uniformity

Consistency is the hallmark of a good TMR program. Cows perform best when the ration is the same every day and every bite is the same. Inconsistency in the ration leads to digestive upsets, reduced intake, and lower production.

Ration consistency starts with consistent ingredients. Use the same forages, grains, and supplements from day to day. When you change ingredients, make the change gradually over several days to allow the rumen microbes to adapt.

Ration consistency also requires consistent mixing. Use the same loading order, mixing time, and mixer speed every batch. The mixer should be maintained in good condition so it performs consistently.

Check ration consistency by sampling the TMR from different parts of the mixer and the bunk. The nutrient content and particle size distribution should be similar across all samples. If you see wide variation, the mixing process needs adjustment.

Also check the consistency of the TMR from batch to batch. Sample each batch and compare the results. If one batch is different from the others, investigate the cause. It may be a weighing error, a moisture change, or a problem with the mixer.

The consistency of the feed delivery also matters. The TMR should be delivered evenly along the bunk so all cows have equal access. Uneven delivery can cause competition at the bunk and reduce intake for subordinate cows.

Feeding Different Groups on TMR

Most dairies feed more than one group of cows, and each group has different nutritional needs. The TMR system allows you to formulate and feed different rations to different groups, but this adds complexity to the feeding program.

The most common group separation is by production level. High producing cows receive a more energy dense ration, while low producing cows receive a lower energy ration. This avoids overconditioning low producers and supports maximum production in high producers.

Other groups may include fresh cows, which need a special ration to support the transition into lactation, and dry cows, which need a lower energy ration to prevent overconditioning. Heifers may be fed separately as well.

Each group requires its own TMR recipe and its own mixing schedule. This increases the time and labor required for feeding. Some operations simplify by feeding a single TMR to all lactating cows and adjusting the amount fed, but this is less precise.

If you feed multiple groups, plan the feeding schedule to accommodate each group. Mix the highest producing group first, then the lower producing groups. Clean the mixer between batches if you are concerned about cross contamination, though this is not always necessary.

The number of groups you feed depends on your herd size and facilities. Larger herds can justify more groups because the economies of scale support the additional labor and equipment. Smaller herds may do better with a single group TMR to keep the program simple.

Troubleshooting TMR Problems

When something goes wrong with the TMR program, the symptoms often appear first in the cows. Reduced intake, lower milk production, changes in milk composition, and digestive upsets are all signs that something is wrong. Troubleshooting requires a systematic approach.

Start with the obvious. Check the mixer calibration and loading weights. Verify that the forages have not changed in moisture. Confirm that the ingredients are the same as what your nutritionist formulated. Many problems trace back to a simple error in weighing or loading.

Check the mixing process. Is the mixing time correct? Is the mixer overloaded? Is the loading order correct? Take a particle size sample and compare it to the target. An overmixed or undermixed ration will show up in the particle size distribution.

Check the feed delivery. Is the feed being delivered evenly along the bunk? Are the cows pushing feed out of reach? Is there adequate bunk space for all cows? Bunk management problems can cause intake issues even when the ration is correct.

Check the feed itself. Look for signs of spoilage, mold, or heating. Smell the feed for off odors. Taste a small amount if you are comfortable doing so. Feed that is unpalatable will reduce intake no matter how well it is formulated.

Check the cows. Look for signs of illness, lameness, or other health problems. A health issue can reduce intake in individual cows or across the group. Work with your veterinarian to rule out health problems before making ration changes.

Check the environment. Heat stress, overcrowding, and poor ventilation all reduce feed intake. These factors can override even a well formulated ration. Address environmental issues before changing the ration.

Keep a troubleshooting log. Record the problem, the date, the observations, and the actions you took. This helps you identify patterns and prevents you from repeating the same mistakes.

Recordkeeping for TMR Management

Good recordkeeping is essential for managing a TMR program effectively. Without records, you cannot track trends, identify problems, or make informed decisions. The records do not need to be elaborate, but they should be consistent and complete.

Track feed inventory. Record the amount of each feed purchased and used. This helps you manage feed costs and plan for future purchases. It also helps you identify shrink issues.

Track dry matter intake. Record the amount of TMR delivered to each group and the amount of refusals. Calculate intake per cow and track it over time. A sudden change in intake is an early warning sign of problems.

Track milk production and composition. Record milk yield, milk fat, and milk protein for each group. This information helps you evaluate the ration and identify problems early.

Track forage moisture and quality. Record the moisture content of each forage at each test. Track the results of forage nutrient tests. This information is essential for adjusting loading weights and formulating rations.

Track body condition scores. Record the body condition of cows at regular intervals, such as at dry off, calving, and peak lactation. This helps you evaluate whether the ration is meeting the energy needs of the cows.

Track health events. Record cases of acidosis, displaced abomasum, ketosis, and other metabolic disorders. These events are often related to feeding management and can indicate problems with the ration.

Use a simple spreadsheet or a commercial herd management software to track these records. Review the records regularly, at least monthly, and look for trends. Share the records with your nutritionist and veterinarian so they can help you interpret the data.

When to Call Your Veterinarian or Extension Agent

Most TMR problems can be solved with adjustments to the feeding program. However, some situations require professional help. Knowing when to call your veterinarian or extension agent can save you time, money, and cow health.

Call your veterinarian immediately if you see multiple cows showing signs of acute illness. Symptoms like severe diarrhea, rapid breathing, staggering, or recumbency may indicate acidosis, bloat, or another emergency condition. Do not wait to see if the cows improve on their own.

Call your veterinarian if you see a cluster of metabolic disorders. Several cases of displaced abomasum, ketosis, or milk fever in a short period suggest a systemic problem with the ration or the transition cow program. Your veterinarian can help diagnose the cause and recommend treatment.

Call your veterinarian if cows are off feed for more than 24 hours. Prolonged off feed periods can lead to serious health problems, including fatty liver and ketosis. Early intervention improves the chances of recovery.

Call your extension agent if you need help with ration formulation or feed management. Extension agents can connect you with nutritionists, forage testing services, and educational programs. They can also help you interpret forage test results and make management decisions.

Call your extension agent if you are considering a major change to your feeding system. Whether you are switching from component feeding to TMR, adding a new mixer, or changing your forage program, your extension agent can provide valuable guidance and resources.

Call your nutritionist if you see a persistent decline in milk production or milk components. The ration may need adjustment based on changes in forage quality or cow needs. Do not wait until the problem becomes severe before seeking help.

The key is to act early. Feeding problems that are caught early are usually easy to correct. Problems that are ignored can lead to significant production losses and animal health issues.

Frequently Asked Questions

How long should I mix a TMR in a vertical mixer?

Most vertical mixers require 3 to 7 minutes of mixing time after the last ingredient is added. The exact time depends on your mixer model, the ingredients in the ration, and the load size. Start with the manufacturer's recommendation and adjust based on particle size analysis. Use a Penn State Particle Separator to check the mix and standardize on the time that produces a consistent, well mixed ration. Overmixing grinds the feed too fine and reduces effective fiber, so it is better to mix slightly less than too much.

What is the ideal refusal rate for a dairy TMR?

The target refusal rate is 3 to 5 percent on an as-fed basis. This means cows are eating most of what you deliver but have a small amount left at the next feeding. Refusals below 3 percent suggest cows may be limited in intake, which can reduce milk production. Refusals above 5 percent indicate you are feeding more than the cows need, which wastes money. Weigh refusals regularly and adjust the amount fed to maintain the target range.

How often should I calibrate my TMR mixer scale?

Check the scale accuracy at least monthly, and more often if you suspect problems. To calibrate, park the mixer on level ground, zero the scale, and add a known weight of material that has been weighed on a certified scale. The mixer scale should be accurate within 1 to 2 percent. If the scale is inaccurate, have a qualified technician adjust or replace the load cells. An inaccurate scale will deliver a ration that does not match your formulation, which can reduce production and increase feed costs.

Why is my milk fat dropping on a TMR ration?

A drop in milk fat often indicates a problem with effective fiber in the ration. Check the particle size of the TMR with a Penn State Particle Separator. If too many particles are in the bottom pan, the ration is overprocessed and does not provide enough effective fiber. Other causes include too much starch in the ration, not enough forage, or sorting by the cows. Work with your nutritionist to adjust the ration and address the underlying cause.

Can I feed a TMR once per day?

Yes, many operations feed a TMR once per day successfully. The key is to provide adequate bunk space and manage the bunk carefully. Push up feed several times per day to keep it within reach of the cows. Monitor refusals and adjust the amount fed to maintain a 3 to 5 percent refusal rate. In hot weather or with high producing herds, twice daily feeding may support higher intake and production.

How do I adjust my TMR for wetter or drier forage?

Weigh your forage and calculate the dry matter content. If the forage is wetter than when the ration was formulated, you need to feed more as-fed pounds to deliver the same dry matter. If it is drier, feed fewer as-fed pounds. Test forage moisture at least weekly for fermented feeds like corn silage and haylage. Your nutritionist can provide a spreadsheet or app to make the calculation simple. The key is to adjust promptly when moisture changes.

What is feed shrink and how do I reduce it?

Feed shrink is the difference between the feed you purchase and the feed your cows actually consume. It includes spoilage, waste, errors in weighing, and losses to pests. Measure shrink by tracking feed deliveries, TMR weights, and refusals. Reduce shrink by managing the silage face properly, packing and sealing silage well, storing dry feed in covered areas, cleaning up spills, and calibrating your mixer scale. A shrink rate of 5 to 10 percent is common, but rates above 10 percent indicate significant waste.

When should I call a nutritionist about my TMR?

Call your nutritionist if you see a persistent decline in milk production or milk components, if cows are losing body condition, or if you are changing forages or other major ingredients. Also call if you are considering a major change to your feeding system or if you need help interpreting forage test results. Your nutritionist is a key partner in managing the TMR program and should be involved in any significant changes.

Related Farming Guides

This section will be populated with links to related farming guides on dairy nutrition, herd health management, forage production, and other relevant topics. Check back for updates.

Related Clinical & Scientific Guides

• Animal Welfare Audits: Building a Useful Farm Program
• Feed Additives for Livestock: Probiotics, Enzymes, and More
• Livestock Handling Facility Design and Flow

References

• USDA Farm Management: https://www.farmers.gov/
• FAO Farm Management: https://www.fao.org/farmer-field-schools/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.