The Importance of Grinding Offals in Wheat Milling

When a wheat mill processes grain, the focus is almost always on what comes out as flour. But a significant portion of each batch – the chaff, husks, broken kernels, and fine dust separated during cleaning – never makes it to the flour stream. These materials are collectively known as offals, and in most milling operations, what happens to them determines a large part of the facility’s overall efficiency and profitability. Grinding offals is the process that transforms these apparent leftovers into a commercially valuable, nutritious product for animal feed – and it is far more deliberate and technically involved than it might seem.

What exactly are offals in wheat milling? 🔗

In the context of wheat milling, offals are all the non-flour materials separated during the cleaning and milling stages. This is distinct from the culinary use of the word. Wheat milling offals form a continuum of products ranging from fibrous coarse brans produced in early grinding steps to starchier fractions from later stages. They include chaff (the lightweight outer coverings removed from grain), husks (the harder outer layers stripped before milling begins), broken kernels that fail quality checks, fine dust, and small foreign plant matter that arrives with wheat from the field.

According to Feedipedia, typical milling extraction rates range from 75 to 80 percent flour yield, which means 20 to 25 percent of the incoming wheat ends up as offals. Wheat bran alone represents roughly 50 percent of those offals and 10 to 19 percent of the kernel, depending on the variety and milling process. This is not a trivial volume – a mill processing 100 tons of wheat per day can expect to generate 8 to 12 tons of offals that need to be managed one way or another.

Wheat middlings, one of the most commercially recognized offal products (also known as wheat mill run or wheat midds), are composed of bran particles, germ, some starchy endosperm, and other fractions from the tail of the mill. Despite being informally described as “floor sweepings” in some trade contexts, these materials are captured well before they would ever reach the floor – and they carry real nutritional value.

The nutritional case for grinding offals 🔗

The reason grinding offals is worth doing at all comes down to what these materials contain. Wheat offal generally contains 12 to 17 percent protein, 8 to 12 percent fibre, and an energy value of 2,500 to 2,800 kcal/kg. It is also a meaningful source of B vitamins, magnesium, phosphorus, and zinc. Feedipedia notes that wheat bran is relatively rich in protein at 14 to 19 percent dry matter, with mineral content of 4 to 7 percent dry matter, including calcium and phosphorus – nutrients that support bone development and metabolic function in livestock.

Research published in Translational Animal Science confirms that wheat co-products – including bran, middlings, millrun, shorts, and red dog – vary in their nutrient profiles depending on the milling process and grain variety, but all offer meaningful energy and protein contributions to animal diets. Wheat bran also improves feed palatability, which is a practical advantage when formulating rations for livestock.

That said, not all offals are nutritionally equal. According to research cited in Nutrient Requirements of Dairy Cattle (NCBI), the chemical composition of wheat middlings varies depending on wheat type, variety, growing conditions, the grade of flour produced, and the proportion of bran included. This variability means mills must know their own product streams to make accurate feed formulation claims.

How the grinding process works 🔗

Before any grinding begins, milling facilities collect and sort offals from different equipment streams. Aspiration systems (air-based separators) capture lighter materials like chaff and dust, while screens and sieves collect broken kernels and heavier debris. Keeping these streams organized matters because different fractions have different moisture levels, particle sizes, and nutrient profiles – all of which affect both grinding equipment performance and the final feed product.

Equipment used for grinding 🔗

As detailed by the FAO’s chapter on feed milling processes, hammermills are the most widely used equipment for grinding offals. They work by impact – swinging steel bars force material against a screen or striking plate, holding it in the grinding chamber until it is reduced to the target particle size. Hammermills handle diverse textures well, which makes them suitable for the mix of soft chaff and harder broken kernel fragments typically found in wheat offals. Roller mills use corrugated rolls to crush and cut material, offering more uniform particle size output and fewer fine particles. Attrition mills add a shearing action between rotating discs, useful for smoothing out previously coarse-ground material or handling ingredients with some moisture.

The FAO notes that grinding generally improves feed digestibility, mixing properties, and pelletability, and can increase the bulk density of some ingredients – all of which benefit downstream feed manufacturing.

Particle size and its importance 🔗

Particle size is one of the most critical variables in offal grinding. According to feed manufacturing research, smaller particle sizes increase the surface area per unit volume of feed, which directly improves access by digestive enzymes and enhances nutrient absorption. However, grinding too fine causes its own problems. A review in Translational Animal Science found that for swine, wheat should generally not be ground below 500 microns to avoid risks of stomach ulceration and excessive dust accumulation. For poultry, particle size targets differ by growth phase – younger birds require finer grinds for digestibility, while older birds benefit from coarser material that supports gizzard development.

Practical Farmers of Iowa advises that for ruminants like cattle, grind size is more forgiving – most grains work well as long as they are cracked or crimped. This species-specific requirement is why mills that sort offal streams by fraction can produce targeted products rather than a single generic mix.

Temperature control during grinding 🔗

Heat generated during grinding is a real operational concern. Excessive heat can denature proteins and reduce the nutritional quality of the final product. Most operations monitor grinding chamber temperatures and regulate processing speed, airflow, and screen size to keep temperatures within acceptable ranges. This is especially relevant for offals with higher fat content, where heat accelerates rancidity. Veterinaria Digital recommends maintaining moisture in wheat feed ingredients below 14 percent and regularly monitoring for mycotoxin-producing fungi, since moist conditions can encourage fungal growth in bran and offal-based feeds.

Markets and revenue from processed offals 🔗

The animal feed sector is the primary and most established market for processed wheat offals. Wheat offal is used across a wide range of species: poultry rations incorporate it for energy, fibre, and protein; swine diets use it to promote gut health; small ruminants such as sheep and goats receive it as a supplementary feed, particularly in dry seasons when pasture is limited; and dairy cattle diets incorporate wheat bran and middlings for their protein and fibre contributions to rumen health.

According to NCBI, wheat middlings are commonly used to replace high-starch grains like corn in dairy cattle rations, and their protein content is highly degradable in the rumen, making it readily available for microbial activity. Research cited by Feedipedia shows that supplementing beef steers with wheat offals alongside forage maintained performance comparable to more expensive alternatives, with no negative effects on intake or digestion.

Beyond feed, a peer-reviewed PMC study on sustainable grain by-product valorization notes that the grain processing industry is increasingly exploring higher-value applications for cereal waste – including bioactive compound extraction, biorefinery inputs, and functional food ingredients – which opens additional revenue possibilities for mills that can produce consistently graded offal fractions.

Sustainability and the circular economy argument 🔗

Grinding offals is not just a financial decision – it is increasingly an environmental one. The FAO’s circular economy framework positions the conversion of agricultural processing by-products into productive outputs as directly aligned with multiple Sustainable Development Goals, including SDG 2 (zero hunger through efficient food production), SDG 12 (responsible consumption and production), and SDG 13 (climate action). The FAO and UNEP have jointly emphasized that tackling food loss and waste across the supply chain is a triple-win opportunity for climate, food security, and agrifood system sustainability.

When offals are ground and sold as feed rather than disposed of, they avoid the landfill. Organic waste in landfills breaks down anaerobically, producing methane – a greenhouse gas significantly more potent than carbon dioxide over a 20-year horizon. By converting offals into feed, mills eliminate disposal costs, reduce methane risk, and remove the logistical burden of organic waste transport. Research published in PMC confirms that cereal waste and by-products, though rich in nutrients, are too often discarded rather than valorized – a gap that better processing infrastructure can close.

In addition, locally produced offal-based feeds reduce the need to transport feed ingredients over long distances, which cuts transport-related emissions and supports regional feed supply chains. For mills in grain-surplus regions, this creates a localized circular loop: wheat is grown, cleaned, milled, the flour goes to food production, and the offals return to local livestock farming as feed.

Quality control and storage of ground offals 🔗

The value of ground offals is only realized if quality is maintained through to delivery. Best practices from Afrimash include storing ground offals in dry, well-ventilated facilities to prevent mould growth and spoilage, monitoring fat content as an indicator of rancidity risk, and gradually introducing offal-based feed into animal rations to allow digestive adaptation. Veterinaria Digital specifically flags the risk of mycotoxins – particularly from Salmonella and Clostridium – in stored bran and offal products, and recommends routine microbiological testing before use in feed.

Mills that invest in proper sorting, grinding, temperature control, and storage infrastructure are better positioned to command premium prices for their offal products. A milling facility that can guarantee consistent particle size, moisture content, and nutritional profile for its feed-grade products is a more reliable supplier – and that reliability has market value.

What do you think? With 20 to 25 percent of every wheat batch ending up as offals, does the milling industry do enough to capture that value through proper grinding and processing? And as animal feed markets grow alongside global protein demand, how might the economics of offal processing shift for smaller-scale mills that currently lack the infrastructure to compete?

References

1. https://en.wikipedia.org/wiki/Wheat_middlings
2. https://www.feedipedia.org/node/726
3. https://afrimash.com/benefits-of-wheat-offal-a-nutritious-feed-for-livesto/
4. https://pmc.ncbi.nlm.nih.gov/articles/PMC11439155/
5. https://www.veterinariadigital.com/en/articulos/importance-of-wheat-in-animal-feed-and-production/
6. https://www.ncbi.nlm.nih.gov/books/NBK600591/
7. https://www.fao.org/4/x5738e/x5738e0j.htm
8. https://en.wikipedia.org/wiki/Feed_manufacturing
9. https://academic.oup.com/tas/article/doi/10.1093/tas/txae106/7714550
10. https://practicalfarmers.org/2019/06/milling-small-grains-for-livestock-feed/
11. https://pmc.ncbi.nlm.nih.gov/articles/PMC10606821/
12. https://www.fao.org/land-water/overview/onehealth/circular/en/
13. https://www.fao.org/newsroom/detail/FAO-UNEP-agriculture-environment-food-loss-waste-day-2022/en