Modern compound feed production involves much more than simply mixing raw materials. Feed manufacturers must simultaneously consider hygiene, animal health, efficiency, and legal requirements. Our annular gap expander is a key technology in this field.
During expansion, feed components such as grains and protein sources are treated with pressure, moisture, and heat. The result is hygienic, highly digestible feed of consistent quality that offers a wide range of benefits. Cell structures are broken down, germs such as salmonella are reliably eliminated, and digestibility is increased. In addition, the nutrients in the feed become more accessible to animals, which is ideal for pigs, poultry, and dairy cattle.
Using an expander improves not only the quality of the feed but also the efficiency of the entire production line. Thanks to pre-treatment in the expander, throughput of our downstream pellet mill can increase by over 25%, and sometimes up to 50%. At the same time, pellet quality improves due to a significant reduction in abrasion values and increased pellet strength.
Impactful technology: how the process works
The expander is driven by an energy-efficient gear with an integrated main bearing. Inside, a thick-walled mixing tube with wear-resistant dosing, mixing, and kneading elements ensures intensive feed conditioning. The necessary counterpressure is generated by a hydraulically adjustable cone which, together with a fixed outlet ring, forms an annular gap. This design allows for continuous adjustment of pressure, temperature, energy input, and expansion intensity – even during operation. This enables a wide variety of products and recipes to be processed flexibly and gently, whether in preparation for pelleting or as a stand-alone treatment in feed production. Depending on the application, the expander operates at pressures between 5 and 120 bar and achieves outlet temperatures of 90 to 130°C – and even higher in special applications.
At the end of the process, the product leaves the machine via the cone. The sudden drop in pressure causes the product to expand, resulting in some water evaporating immediately (flash evaporation). Typically, downstream cooling is sufficient, and post-drying is usually unnecessary. A downstream crushing device (e.g., a structurizer or crusher) achieves the final structure and size of the expanded product.
Feed production with the expander - clean, safe, and strong
A key objective of our annular gap expander is to ensure the hygienic quality of the feed. This is especially important for sensitive feeds, such as those for laying hens, which are often not pelleted. Pigs and poultry also benefit from the germ-reducing effect of our expander because they are susceptible to pathogens. In addition to improving hygiene, the expander increases the availability of essential nutrients, such as starch and protein. This promotes digestion and improves the performance and cost-efficiency of animal nutrition. In pigs, expander treatment improves starch modification in the anterior small intestine, thereby preventing excessive amounts of undigested starch from reaching the large intestine. This improves intestinal health and animal performance. This effect is particularly evident in piglets. Studies show that better starch modification leads to higher weight gain and lower losses, especially during the sensitive rearing phase. At the same time, broken-down grain stimulates digestive enzyme activity in the animal's body. This makes it easier for the animals to transition to grain-based compound feed and increases their feed intake.
Downstream structurizers or crushers give the expanded product a defined shape and consistency. Compared to mealy compound feed, the expanded feed is more water-soluble, making it ideal for liquid feeding systems in pig farming. This advantage remains even after pelleting. Laying hens also benefit from the greater homogeneity of the expanded feed. It prevents selection by the animals and reduces the segregation of raw materials during transport or storage. Last but not least: The addition of steam during the expansion process improves the smell and taste of the feed. This is a decisive factor for high acceptance in all animal species.
Production line compound feed
Main machines of a production line for the manufacture of compound feed pellets
Better for animals and the budget
Using the expander also pays off economically. Studies show that, despite its reduced energy content, expanded and subsequently pelleted feed can achieve the same performance as traditional pellet feed thanks to better digestion and utilization of the main nutrients. In broiler farming, up to 70 kilocalories per kilogram of feed can be saved, reducing costs by five to seven euros per ton, depending on the recipe. The technology also benefits. The expander performs most of the mechanical work before pelleting, allowing the pellet mill to increase its output by 20 to 30 percent while significantly reducing wear. This protects tools, saves energy, and extends the service life of the plant.
Our expander offers a flexible and powerful solution that successfully combines animal welfare, feed quality, and economic efficiency to produce a high-quality end product.
