Introducing an alternative design of feed processing line to protect heat-sensitive materials
Compound feed is a mixture of main ingredients, including grains, protein supplements and by-products, and feed additives (micro-ingredients) such as minerals, vitamins, commercial enzymes, probiotics and prebiotics.
In conventional feed mills, these 2 categories of ingredients are placed in a mixer to produce a uniform mixed feed. Then this feed is transported to the conditioner where the feed is subjected to thermal processing and continues on, passing through a hot die to produce hot pellets. In the next step, the temperature and moisture of pellets are reduced by a cooler. For a typical design of such a feed processing line see Figure 1. In this kind of feed processing line both main ingredients and feed additives are cooked.
However, thermal processing is a double-edged sword; the applied heat has both positive and negative effects on the main ingredients, but its effects on feed additives usually are negative. Many feed additives, especially commercial enzymes, probiotics and vitamins are expensive and sensitive to heat, thus it is suggested to protect them from the detrimental effects of thermal processing. the feed industry uses three solutions to maintain heat-susceptible materials:
Figure 2 introduces a novel design of the feed processing line. In this design, the main ingredients are grinded, weighed and then subjected to conditioning by a super conditioner. Since the feed additives are not yet added to the main ingredients, it is possible to use higher temperatures (e.g. >90 ˚C) and longer retention times in the super conditioner, for instance for hygienising purposes.
In the dryer and cooler, the conditioned main ingredients will lose the heat and moisture absorbed in the conditioner. After this stage, feed additives are mixed in a micro-mixer to produce a premixture which is added to the main ingredients in a mixer. Then the final mixture is subjected to mild conditioning with only 40-50 ˚C (by a small amount of steam or even hot water) before being pelleted by the pellet mill.
In spite of mild conditioning at this stage, the quality of the pellets (e.g. the pellet durability index and hardness) will remain satisfactory because of the previous conditioning. Practical results show that the energy consumption of pellet mills has decreased and the output of pellets (tonnes/h) and the longevity of the die have increased in this design. After the pelleting process is complete, the temperature and moisture of pellets are reduced by a cooler.
Conditioned mash – an overlooked feed form for livestock
Pelleting is an expensive and bottleneck process in feed manufacturing but pellet is the major form of feed used and has many advantages compared to mash form.
The suggested feed processing line has advantages and disadvantages compared with a conventional feed processing line.
Wageningen-based collaboration on pelleting co-products
To replace cereals in animal feed with less sticky co-products from circular agriculture, finding out how animal feed pellets stay intact is paramount.
Feed additives such as vitamins, probiotics, and commercial enzymes are expensive components of modern animal feed. Most of these materials are heat-sensitive. To maintain the efficacy of these materials, the feed industry uses different strategies, including excess use of materials, a heat-resistant or coated form for some materials and vacuum coating technology. Nevertheless, these methods are expensive and have limitations.
An alternative method to protect feed additives is to install a mixer layout after thermal processing and to add feed additives to the mixer to avoid the high temperatures.
Co-author: Ali Bazgir, Asiab Machine Iranian Company
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