Wheat middlings are a byproduct of flour milling, made up of fine particles of bran, germ, shorts, and residual flour that get separated from the white endosperm during processing. They are one of the most widely used feed ingredients in livestock and poultry nutrition, valued for a moderate protein content that typically runs around 16 to 18 percent and a high dietary fiber fraction. While their primary role is in animal feed, wheat middlings also show up in feed manufacturing as a pellet binder and are drawing renewed interest as a potential ingredient in human functional foods.
How Flour Milling Creates Wheat Middlings
When a wheat kernel enters a commercial flour mill, the goal is to extract as much white endosperm as possible. The kernel gets cracked open, and a series of rollers, sifters, and purifiers progressively separate the starchy interior from the outer bran layers and the oil-rich germ. Each pass through the system generates streams of particles that vary in size and composition. The finest, starchiest fractions become white flour. Everything else, the bits of bran, germ, and endosperm that didn’t make the cut, gets classified into byproduct streams.
Wheat middlings (often called “wheat midds” in the feed trade) sit in the middle of that byproduct spectrum. They contain a mix of fine bran particles, wheat shorts, wheat germ fragments, and small amounts of flour still clinging to those pieces. Related byproducts include wheat bran (coarser, higher in fiber), red dog (finer, starchier, closer to flour), and wheat mill run (a catch-all blend). The distinctions matter because each stream has a different nutrient profile, and the labels are defined by industry standards that set maximum crude fiber limits. Wheat middlings, for instance, are generally required to contain no more than 9.5 percent crude fiber.
The feed industry and the flour milling industry grew up together. Many of the earliest commercial feed companies were flour mills looking for a profitable outlet for their byproducts. That history explains why wheat middlings remain so deeply embedded in livestock rations today: they were available in large, consistent volumes before purpose-built feed ingredients even existed.
Nutritional Profile
Wheat middlings carry a protein content that averages around 16 to 18 percent, depending on the source and how the mill operates. A study analyzing multiple samples found an average crude protein of about 17.7 percent, along with roughly 4 percent fat and more than 36 percent total dietary fiber.1PubMed Central. Nutrient composition and digestibility of energy and nutrients in wheat middlings and red dog fed to growing pigs The starch content sits around 20 percent, which is considerably lower than corn or barley but enough to contribute meaningful energy. That high fiber fraction is one of the defining characteristics: it provides bulk and supports gut health in ruminants, though it limits the energy density that monogastric animals like pigs and chickens can extract.
The amino acid profile is decent but not outstanding. A large survey of 14 different wheat middling sources reported average lysine at 0.66 percent, threonine at 0.54 percent, methionine at 0.25 percent, and tryptophan at 0.19 percent.2Oxford Academic (Journal of Animal Science). Variability among sources and laboratories in analyses of wheat middlings Lysine, the first limiting amino acid for pigs and poultry, is lower in wheat middlings than in soybean meal, which is why midds are usually combined with protein-rich ingredients rather than used as a sole protein source. Phosphorus levels tend to be relatively high (around 0.97 percent in that same survey), though much of it is bound in phytate and not fully available to non-ruminant animals without enzyme supplementation.
Compared to red dog, a lighter and starchier milling byproduct, wheat middlings contain roughly twice the fiber and about half the starch.1PubMed Central. Nutrient composition and digestibility of energy and nutrients in wheat middlings and red dog fed to growing pigs That makes middlings the better choice when a nutritionist wants to add fiber and bulk to a diet, and red dog the better choice when energy density matters more.
Why Composition Varies So Much Between Sources
One of the persistent challenges with wheat middlings is that “wheat middlings” from one mill can be quite different from “wheat middlings” from another. The survey of 14 sources found statistically significant variation in almost every nutrient measured, with calcium ranging from 0.08 to 0.30 percent and selenium from 0.05 to 1.07 mg/kg, a twenty-fold difference.2Oxford Academic (Journal of Animal Science). Variability among sources and laboratories in analyses of wheat middlings That kind of spread can create real problems when formulating precise diets, especially for poultry and swine where nutrient margins are tight.
Part of the explanation is structural. Mills vary in how thoroughly they extract flour, and that affects how much residual endosperm clings to the bran particles in the middlings stream. The same study identified a useful shortcut: bulk density. “Heavy” middlings (those with a higher bulk density, above about 335 grams per liter) tend to carry more attached flour, which makes them lower in protein, lysine, phosphorus, and fiber. “Light” middlings (below about 310 grams per liter) represent cleaner bran with less residual starch, so they’re higher in protein and fiber.2Oxford Academic (Journal of Animal Science). Variability among sources and laboratories in analyses of wheat middlings Bulk density, which is easy and cheap to measure, correlated strongly with crude protein and neutral detergent fiber. For feed buyers, a quick density check can flag whether a batch of middlings is running heavier or lighter than expected before committing to a purchase.
Wheat Middlings in Cattle and Sheep Diets
Ruminants are the natural home for wheat middlings. Cattle and sheep have the microbial fermentation capacity to break down the high fiber fraction that limits middlings’ value for other species, and research consistently shows that midds can substitute for traditional energy concentrates like corn and barley without hurting performance.
In beef cattle, a study comparing wheat middlings to conventional concentrate sources found no differences in average daily gain, feed intake, or feed efficiency between the two diets. Dry matter digestibility was also unaffected. The researchers concluded that wheat middlings could serve as a direct alternative to corn or barley in growing and finishing rations.3Canadian Journal of Animal Science. Effects of feeding wheat middlings on production, digestibility, ruminal fermentation and carcass characteristics in beef cattle The rumen fermentation pattern did shift, with total volatile fatty acid production increasing and the acetate proportion dropping on the middlings diet, but that didn’t translate into any measurable change in growth or carcass traits.
In dairy ewes, a diet containing 50 percent wheat middlings supported the same milk yield and milk composition as a corn-based control, with one bonus: the middlings diet actually increased milk fat percentage and milk fat yield.4PubMed. Effect of wheat middlings-based total mixed ration on milk production and composition responses of lactating dairy ewes Neutral detergent fiber digestibility was also higher on the middlings diet, suggesting the rumen microbes were handling that fiber fraction well. Protein, lactose, and milk clotting properties were unchanged.
Lambs respond similarly. A feeding trial showed that including wheat middlings in a total mixed ration improved final live weight, daily gain, and feed conversion ratio compared to the control diet. Slaughter weight and cold-carcass dressing percentage both improved as well, while other carcass traits were unaffected.5Elsevier. Feeding of wheat middlings in lamb total mixed rations: Effects on growth performance and carcass traits Across all three ruminant species, the pattern is the same: wheat middlings maintain or slightly improve performance, often at a lower ingredient cost than the grain they replace.
Limitations in Swine Diets
Pigs tell a different story. Because they lack a rumen, pigs can’t ferment the high-fiber fraction of wheat middlings as efficiently, and the energy they extract per kilogram is lower than from corn. Research on finishing pigs found that increasing the proportion of wheat middlings in the diet led to slower growth and worse feed efficiency in a dose-dependent manner.6Journal of Animal Science. Effects of dietary wheat middlings, distillers dried grains with solubles, and choice white grease on growth performance, carcass characteristics, and carcass fat quality of finishing pigs Feed intake itself didn’t change much, suggesting that palatability wasn’t the issue; the pigs just couldn’t convert the feed as efficiently.
On the carcass side, the effects were mixed. Pigs on higher middlings inclusion showed lower carcass yield and lighter hot carcass weights, which matters economically because pigs are typically sold on a carcass-weight basis. But backfat depth also decreased and the fat-free lean index went up, meaning the carcasses were leaner. At the same time, jowl fat iodine value increased, which indicates softer, less saturated fat, a quality concern for some pork processors. Adding supplemental fat (choice white grease) to the diet helped offset some of the growth penalties but didn’t fully compensate for the effects on carcass yield and fat quality.6Journal of Animal Science. Effects of dietary wheat middlings, distillers dried grains with solubles, and choice white grease on growth performance, carcass characteristics, and carcass fat quality of finishing pigs
The practical upshot for swine producers is that wheat middlings have a role in pig diets, but inclusion rates need to stay moderate, especially in finishing phases when growth rate and carcass quality have the most economic impact. They’re more commonly used in gestating sow diets where the extra fiber is actually beneficial for gut fill and satiety, and the growth-rate penalties don’t apply.
Poultry Feed and Enzyme Strategies
Chickens face similar digestibility challenges to pigs when it comes to wheat-based feed components, but the poultry industry has developed a practical workaround: exogenous enzymes. The non-starch polysaccharides in wheat and its byproducts (particularly arabinoxylans) create viscous digesta in the bird’s gut, which reduces nutrient absorption and can cause wet, sticky litter. Adding xylanase, an enzyme that breaks down those polysaccharides, reduces gut viscosity and improves the bird’s ability to extract energy.
Research on broilers fed wheat-based diets showed that adding xylanase alone improved body weight gain by around 16.5 percent, while phytase (which releases phosphorus bound in phytate) improved it by a similar margin. Used individually, each enzyme produced numerical improvements in energy extraction that didn’t reach statistical significance. But when the two enzymes were combined, the energy improvement became significant, and digesta viscosity dropped across all sections of the intestine.7PubMed. Influence of phytase and xylanase, individually or in combination, on performance, apparent metabolisable energy, digestive tract measurements and gut morphology in broilers fed wheat-based diets containing adequate level of phosphorus The combination also reduced the relative weight and length of the small intestine, which is considered a sign that the gut is working more efficiently and not having to compensate for poorly digested feed.
Beyond their nutritional contribution, wheat middlings serve a mechanical role in poultry feed manufacturing. When used as a pellet binder at inclusion rates around 50 kilograms per ton, middlings significantly improved pellet quality by reducing the proportion of fines (crumbled pellet dust) compared to unbounded feed. The same study found that birds eating the better-formed pellets with wheat middlings showed improved growth performance and better nutrient digestibility.8PubMed Central. Effect of feeding wheat middlings and calcium lignosulfonate as pellet binders on pellet quality growth performance and lipid peroxidation in broiler chickens This dual function, contributing nutrients while simultaneously holding pellets together, makes wheat middlings particularly cost-effective in pelleted poultry diets.
Feed Processing and Pellet Quality
The physical properties of wheat middlings make them naturally suited to pelleting. Their moderate starch content gelatinizes during steam conditioning, acting as a binding agent that holds pellet structure together. Research from the early days of systematic feed processing showed that steam conditioning a swine diet containing wheat middlings before pelleting produced more durable pellets and caused less starch damage than dry pelleting. It also reduced the electrical energy consumed per ton of feed produced.9Journal of Animal Science. Effects of Steam Pelleting Conditions and Extrusion Cooking on a Swine Diet Containing Wheat Middlings The pellet production rate increased as well, meaning the mill could push more feed through the die per hour.
The catch is that generating steam requires energy too, so when total energy (electrical plus thermal) was accounted for, steam pelleting used more total energy than dry pelleting. The tradeoff is almost always considered worthwhile because pellet durability matters for the entire downstream supply chain. Crumbly pellets generate fines during transport and handling, and fines reduce feed intake in both pigs and poultry. A more durable pellet means less waste, better feed conversion, and lower dust exposure in barns.
Emerging Interest in Human Food Applications
Wheat middlings have traditionally been seen as animal feed, but food scientists have started looking at them differently. The broader category of wheat milling co-products, which includes bran, shorts, red dog, and middlings, is rich in dietary fiber, micronutrients, and phytochemicals that are stripped away during white flour production. Research characterizing these co-products found that bran had the highest fiber and mineral content, while shorts (a component of middlings) carried intermediate levels of both, along with respectable antioxidant activity.10Journal of Cereal Science. Physicochemical and functional characterization of wheat milling co-products: Fine grinding to achieve high fiber antioxidant-rich fractions
Particle size turns out to be a key variable for human food use. Fine grinding of bran fractions changed their functional properties in ways that could matter for product development. Smaller particles had higher protein and starch content (from better breakage of the bran’s cellular structure), while larger particles retained more fiber, more ash, and actually showed greater antioxidant activity as measured by a standard radical-scavenging assay.10Journal of Cereal Science. Physicochemical and functional characterization of wheat milling co-products: Fine grinding to achieve high fiber antioxidant-rich fractions The larger bran fractions also had higher water-holding and oil-holding capacity, properties that affect texture in baked goods, cereals, and extruded snacks.
The practical barrier to using these co-products in human food at scale is partly regulatory and partly sensory. Consumers expect refined white flour to be smooth and neutral-tasting. Adding bran or middlings fractions changes color, texture, and flavor in ways that require careful formulation. There’s also the challenge of ensuring food-grade handling and traceability through a supply chain that has historically treated these streams as animal feed.
Storage, Oxidation, and Shelf Life
Wheat middlings contain wheat germ fragments, and wheat germ is notoriously unstable once it’s been separated from the intact kernel. The germ’s oil fraction is rich in polyunsaturated fatty acids, and the mechanical damage from milling exposes those lipids to air and to the grain’s own enzymes (particularly lipase and lipoxygenase), which accelerate oxidation.11PubMed Central. Wheat Germ and Lipid Oxidation: An Open Issue The result is a product with a relatively short shelf life if not stored properly. Off-flavors, rancidity, and nutrient degradation can all develop over time.
For animal feed applications, this is manageable. Middlings are usually consumed within weeks of production, and feed mills have established inventory turnover practices that minimize storage time. Antioxidant additives can also extend stability when longer storage is needed. But for any potential human food use, the oxidation problem becomes a more serious hurdle. Stabilization treatments like heat treatment, infrared processing, or controlled-atmosphere storage can extend shelf life, though each adds cost and complexity. The research on wheat germ stabilization is more advanced than on middlings specifically, since germ has long been sold as a standalone health food ingredient, but the underlying chemistry is the same: polyunsaturated fats plus oxygen plus enzymes equals rapid quality loss.
Horses and Other Niche Applications
Outside the major livestock species, wheat middlings also show up in horse feed, where they’re valued for the same moderate protein and digestible fiber profile. In equine nutrition, midds serve as a convenient source of calories and protein that’s less energy-dense than straight grain, making it useful for horses that don’t need the concentrated punch of corn or oats. The fiber fraction is gentler on the equine hindgut than starch-heavy feeds, which can trigger digestive upset when overfed. Commercial horse feeds frequently list wheat middlings on their ingredient panels, often as one of the top three or four components by weight.
Wheat middlings have also found niche use in aquaculture feeds and pet food, where they serve similar roles as a mid-range energy and fiber source. In these applications, the same variability concerns apply. A pet food manufacturer buying middlings from multiple mills will see different nutrient profiles batch to batch, which means ongoing quality testing is part of the cost of using the ingredient. For large-scale feed producers, this is routine. For smaller operations, it can be a reason to prefer more standardized ingredients even if they cost more per ton.