“Many variables affect the pellet quality. We should distinguish between parameters originating from the ingredients and formulation, and process and technology related factors. Technology plays a vital role, as it is directly linked to a feed miller’s objective of producing pellets that are as hard as required and maintain a high and constant throughput while keeping energy costs at the lowest level possible.”
In the animal feed industry, compound feed is mainly used in pellet and granule forms. It is observed that the pellet form has been preferred more in recent years due to its features such as ease of transportation and its positive effects on the performance of the consuming animal. These positive effects are thought to be largely related to the physical quality of the pellet. The quality of the pellet is directly related to the formulation of the feed and the technology implemented to produce the pellet.
We asked many questions about pellet feed to Stefan Hoh, Head of Market Segment Feed Milling and Premix at Bühler Group. Hoh, who is responsible for the Group’s global animal feed business, headquartered in Changzhou, China, gave important information on the latest innovations in quality pellet feed production, pellet and granulated feed production technologies.
PELLET FEED OR GRANULE FEED?
Whether pellet feed or granule feed should be preferred in animal nutrition?
From a nutritional perspective, the selection of the appropriate type of feed depends to a large extend on the animal species. But also, other factors such as the age of the animals, their stage in the growing cycle, as well as the feeding method need to be taken into account.
For broilers, it has been proven that pelleted or granulated feed leads to a better performance in the starter phase of growth as compared to mash feed. However, in their middle and final fattening stage, the performance is improved by providing feed as meal.
In pigs and poultry, different feed forms (meal, pellets, or granules) can be found. Livestock trials showed a slightly improved feed conversion rate for pigs fed with pellets, as compared to control groups fed with mash or pellets of lower quality, respectively.
For cattle and dairy cattle feed, barn automation is a driver for the increasing use of feed pellets. Cows consume pellets more rapidly than other forms of feed. This is important because eating may have a limiting effect on milk production.
In conclusion, the feed form needs to be adjusted to the species, physiology, digestive system, and the age of the animals. In-line sensors in combination with advanced process control algorithms enable a consistently optimized nutritional value at minimum production costs and lead to a decisive competitive edge along the entire value chain.
PRODUCE QUALITY FEED PELLETS
What are the ways to produce quality feed pellets?
Many variables affect the pellet quality. We should distinguish between parameters originating from the ingredients and formulation, and process and technology related factors.
Regarding the ingredients and formulation, there are feedstuff materials that pelletize well and produce a durable pellet, and there are others that won’t. While cereal grains make up a major part of most feed formulas, fats and oils, being present in much smaller amounts can have the same, or even a much greater impact on pellet quality. For high-fat formulations, better pellet quality can be expected when fat is bound in the raw materials compared to adding fat as a liquid in the conditioner. Moreover, corn deteriorates the pellet quality and wheat promotes the pellet quality. In addition, raw fiber with a high share of cellulose promotes the pellet quality, whereas a high share of lignin undermines pellet quality.
From a technological perspective, the conditioning process is of utmost importance. Especially the moisture content and temperature of the mash at the press inlet are decisive factors. Both are greatly influenced by the quantity and characteristics of the steam during the conditioning process. As rule of thumb, the pellet quality can be improved by increasing the conditioning temperature, while there is a trade-off at temperatures above 85 °C, where little to no further improvement of the pellet quality can be expected. With regards to die specifications, the ratio of hole length and hole diameter, as well as the dwell time in the die, are of great importance. Other determining factors are the feeding rate, the distribution of the mash in the pelleting chamber, as well as the roll gap. All critical parameters of the pelleting process (motor load, throughput, temperatures, wear, etc.) should be constantly monitored, e. g. by an integrated process line or plant control system. With WinCos and Mercury, Bühler provides two powerful, future-proof tools to monitor and control these parameters and offer further insights for customers thanks to cloud services.
What is the place of technology in the production of quality pellets?
Technology plays a vital role, as it is directly linked to a feed millers’ objective of producing pellets that are as hard as required and maintain a high and constant throughput while keeping energy costs at the lowest level possible. Furthermore, the pelleting process has a very high significance for the hygienization of the feed. Pathogenic germs like salmonella can be significantly reduced in the conditioning process with the appropriate temperature and residence time. With Hymix Plus, Bühler provides a conditioning solution, ensuring a hygienically safe process start and 100% of the feed mash being heated up to the desired target temperature. Supplementary automation solutions enable traceability, prevent cross-contamination, and help to reduce undesirable side-effects of the pelleting process such as the reduction of vitamins and enzymes.
It must be said that technology can do a great deal to support operators in achieving highest production efficiency and product quality but can’t compensate for lack of fundamental knowledge and practical knowledge. Profound operator training, both in theory and practice, is indispensable and key to success. The upskilling of operators becomes even more important as digital technologies are emerging rapidly also in the feed industry. Ideally, human knowledge and technology go hand in hand and synergize each other.
What is the effect of particle size on the pelleting process?
The particle size is very important for the pellet quality, especially in terms of pellet hardness. Fine particles act like a glue and form a better and tighter framework due to their larger overall surface area, strengthening the cohesive forces. Therefore, pellet quality improves with decreasing particle size. In contrast, coarse particles are a source of pellet fracture because they have a smaller surface area, which means that less liquid and solid bridges can be formed on their surface. The risk of transverse cracks increases with increasing particle size in relation to the pellet diameter.
LATEST TECHNOLOGICAL DEVELOPMENTS
What are the latest technological developments in the pelleting process?
The use of “no-loss” processes such as Hymix Plus, ensuring that the first particles are already heated up to the target temperature at start-up, have emerged since feed safety requirements have increased. For the pellet mill itself, we can see a clear trend towards the (partial) automation of machine features and parameters, such as the use of automatic roll gap adjustment and sensors for monitoring roll slippage. Furthermore, and especially since the drastic increase of raw material costs, in-line sensors for moisture, fat and crude protein have become crucial to make highest use of raw materials and optimize feed performance. Also, there is a shift in mindset not to only optimize a single machine or process parameter, but to put the product quality at the forefront of each optimization step. With MoisturePro, Bühler has a solution which ensures a constant pellet moisture end of line after the cooler by a smart control of all upstream critical process parameters, such as mixing, conditioning, etc.
Have there also been new developments in the production of granulated feed, such as crumbles?
A recent development is roller mills where the rolls can be changed without having to remove the bearings and drive overdrive stations. Both machine uptime and operator convenience are greatly improved. Also, as we understood the positive correlation of particle size with animal health and performance, in-line sensors for monitoring the particle size have emerged and gained great interest from customers. A next consequent step we expect soon is the adjustment of critical processes and related parameters based on actually measured vs. desired particle size distribution.
THE HUMAN FACTOR
Since we focused until now on technological aspects – how about the human factor?
Technology can do a great deal to support operators in achieving highest production efficiency and product quality but can’t compensate for lack of fundamental and practical knowledge. Profound operator training, both in theory and practice, is indispensable and key to success. The upskilling of operators becomes even more important as digital technologies are emerging rapidly also in the feed industry. Ideally, human knowledge and technology go hand-in-hand and synergize each other. Therefore, Bühler – as technology leader for the feed production industry – has set up world-class training facilities throughout the world, such as the Swiss Institute of Feed Technology (SFT) or the AFT as the respective counterpart for the Asian region. The future in feed milling is not either human- or technology-driven, it’s about combining both worlds to create the best experience, yield and profit possible for feed producers.