High-yielding cows and beef cattle require large amounts of high-quality protein. Since the microbial proteins in the rumen are not enough to meet this demand, rumen-protected components must be added to their feed. Following the EU-wide ban on formaldehyde, there is a need for sustainable, animal-friendly alternatives. Hydrothermal processes offer one solution.
Animal Feeder
Amandus Kahl
Cows cover a large part of their protein requirements from rumen microbes. However, this supply of protein reaches its limit as the animal’s performance increases. In order to supplement this supply, high-quality feed components that are not pre-digested in the rumen must be fed to the animal. These components are directly available for resorption in the small intestine. For many years, treating feed with formaldehyde has been an effective way to increase rumen stability. Following the EU Commission’s Implementing Regulation (EU) 2022/1104 banning formaldehyde, new solutions have emerged: hydrothermal and pressure hydrothermal processes. These processes offer a promising alternative that is completely free of critical additives for modern, healthy animal nutrition.
TECHNICAL PROCESSES FOR INCREASING RUMEN STABILITY
Hydrothermal and pressure hydrothermal processes protect proteins from premature degradation using physical processes such as heat, pressure, and moisture. These processes do not use chemical additives and meet the key requirements of modern feeding concepts. They are energy-efficient, sustainable, and economical.
A key benchmark for evaluating these processes is the UDP value (UnDegradable Protein). The UDP value describes the proportion of rumen-stable protein in total crude protein (CP) and indicates the percentage of proteins that are rumen-stable and directly available for digestion in the small intestine. The rumen stability of feed must be calculated by taking into account a specific retention time in the rumen. For high-yielding cows, about 8% of rumen contents are estimated to enter the intestine per hour. The UDP content of feed is typically calculated based on an 8% passage rate and expressed as UDP8.
The efficiency of technical feed processing, or rumen stability, is assessed using various testing and estimation methods. These results are then used to evaluate the relative effectiveness of different processes or treatments compared to the initial product. Since the results vary, it is necessary to continuously sample the raw material and finished product to generate a stable and reliable database.
The pressure-hydrothermal expander process, developed by the Reinbek-based mechanical engineering company Amandus Kahl, is a proven method for increasing the UDP value. In this process, the feed protein undergoes treatment with steam, pressure, and temperature to specifically alter its structure and increase rumen stability. After preliminary grinding with a crushing roller mill and steam preconditioning in a continuous mixer, the process material is briefly heated to high temperatures under high pressure using the Kahl crown expander (High Temperature Short Time or HTST).
The hot, expanded product is then fed into the long-term conditioner, also known as a hydrothermal reactor. This machine maintains the product’s temperature near the boiling point for approximately 20 minutes, significantly increasing the UDP value. At the same time, digestibility in the small intestine improves. Finally, the expanded product, or expandate, is cooled in the belt cooler, resulting in a stable and nutrient-rich end product.
Thanks to its uniform particle structure, the expanded product is particularly resistant to segregation in total mixed rations (TMRs), which largely prevents selective feed intake. Alternatively, the expanded product can be pelleted with minimal extra energy.
SUSTAINABILITY AND ECONOMIC ADVANTAGES
In addition to improved rumen stability, sustainability is a key factor in feed production. The pressure-hydrothermal expander process offers several advantages in this regard. Targeted control of heat, pressure, and moisture minimizes electrical energy consumption. Unlike purely hydrothermal processes, which require energy-intensive hot air drying, the final product only needs to be cooled by ambient air in the belt cooler. This saves considerable energy and reduces the carbon footprint of feed production.
Furthermore, treatment in the Kahl expander line changes the protein structure, improving the digestibility of the nutrients it contains. Expansion increases the bypass protein digestibility in the intestine, especially with rapeseed meal and other mono-components. This increases overall feed conversion and improves feed efficiency. From an economic perspective, improved protein utilization allows for a reduction in feed consumption while maintaining milk and fattening yields.
CONCLUSION
The growing demand for sustainable and efficient animal nutrition makes it clear that innovative solutions are needed – not just as a substitute for formaldehyde, but also as a sustainable, resource-efficient feeding strategy. Pressure hydrothermal processes are a promising approach that shows modern feed production can be free of chemical additives without sacrificing efficiency or sustainability. The expander technology from Amandus Kahl is a good example of this. Many feed producers worldwide already use it successfully.
About Felix Tometten
As an animal feeding specialist at German engineering company Amandus Kahl in Reinbek, Felix Tometten works in research, development, and internal as well as external consulting. At Amandus Kahl, he acts as a link between technology and animal nutrition.
After completing his Master of Science in Agribusiness and Animal Feeding at the University of Göttingen, he gained experience in poultry consulting at ATR Landhandel and as a district manager at Stader Saatzucht eG.
