1. Overview of extruded feed
The practice of mass production and application of extruded feed in my country is relatively short, and it is currently popular among farmers in the market. Extruded feed is the general term for feed produced by the key process of extrusion and expansion. The feed is continuously mixed, tempered, heated, pressurized, and matured in a high-temperature and high-pressure environment, and the finished feed is suddenly released from the die hole to normal temperature and pressure to form a bulky and porous feed. The application of extruded feed not only breaks through the traditional feed form, but also improves the quality of feed and increases the economic income of farmers. Extruded feed has the following characteristics:
1.1 Improve feed utilization Through high temperature and high pressure mechanical treatment during the extruding process, the cell wall of the fibrous structure can be softened, the 1,4-glucose bond in the starch molecule can be broken, and then low molecular weight, easily absorbed by animals can be produced. Glucose, maltose, etc. substance. At the same time, under the high pressure environment, the protein can be denatured, the peptide chain can be stretched and loosened, the contact with the enzyme in the animal body can be increased, and the nutrient utilization can be increased by 10% to 35%. It is also conducive to the penetration of fat, thereby improving the palatability of the feed and increasing the feeding rate. Some young animals, such as suckling pigs or piglets, calves, etc., are difficult to digest complex plant-based feeds due to their underdeveloped digestive organs. The digestion and utilization rate of feed can be effectively improved by puffing. A number of tests have shown that the extruded feed mainly improves the digestibility of starch and energy, and has relatively little impact on the digestibility of protein, which may be due to the energy-saving effect on protein. Although the digestibility of protein is not significantly improved, it will eventually increase protein deposition efficiency.
1.2 It is more hygienic and reduces the occurrence of diseases Feed often contains harmful microorganisms that cause animal diseases, such as Salmonella, mold, Escherichia coli, neutrophils, etc. The extruded feed is treated at high temperature, which can kill a large number of pathogenic bacteria and eggs contained in the feed, Can effectively reduce the occurrence of animal digestive system diseases. According to data, Salmonella is basically killed after being extruded at a high temperature above 85°C. The number of E. coli in the original feed is 10,000/g, and the number is reduced to 10/g after the puffing treatment. Therefore, the extruded feed is more hygienic and can maintain Water quality and reduce adverse environmental factors of aquaculture, while reducing animal mortality.
1.3 Reducing environmental pollution The reduction of environmental pollution by extruded feed is mainly aimed at aquatic feed. After the extruded feed is processed, the starch is gelatinized and combined with protein, which has a certain bonding or binding force. The feed mostly exists in the form of granules. Generally, it can be kept for 12 hours in the water body, and the general feed dissolves and precipitates quickly after being put into the water body, which not only pollutes the water body, but also causes a lot of waste of feed. Therefore, extruded feed can avoid feed residue in water and reduce water pollution.
1.4 Long shelf life of feed Due to the high-temperature processing of the extruded feed, the moisture contained in it is reduced, and the number of pathogenic bacteria and the number of eggs are effectively controlled under the high-temperature and high-pressure environment. Through the drying and cooling process, the water activity of the feed generally decreases. Dropped to 0.6, or even dropped to 0.4. Therefore, it has a long shelf life and is convenient for storage and transportation.
1.5 Easy feeding and management Extruded feed is easy to raise and manage. In aquaculture, according to different production processes, it can be divided into floating, slow-settling and rapid-settling feeds. Feed types can be selected according to different types of aquatic products to meet different farming needs. Therefore, the use of aquatic expanded feed is helpful for scientific feeding and management, which not only saves a lot of time, but also improves labor productivity. Among them, the floating extruded feed can float on the water surface for a long time without setting up a special feeding platform. It can be fed in the middle of the breeding tank, which improves the feeding efficiency. It is necessary to surface when feeding, and it is also beneficial for the breeder to observe the feeding situation of the fish, and can observe the growth and health status of the fish in time, and carry out feed feeding and fish pond management according to the observation situation, which improves the management efficiency. Feed is one of the future development directions of the breeding industry.
2. Application of extruded feed
2.1 The application of extruded soybean meal, rapeseed meal, straw, bran and other agricultural by-products in livestock and poultry feed can be used as raw materials for livestock and poultry feed. These by-products contain rich application ingredients, but direct feeding will have a low utilization rate , and has not been processed through disinfection and other processes, and contains more microorganisms and eggs, which affects the health of livestock.
2.2 Processing and application of puffed fish feed Fish have high requirements for feed protein during the growth process. Protein content is also a key technical indicator for evaluating fish feed. Too high or too low protein content is not conducive to the feeding and growth of fish. The most important factor for examining the quality of aquatic feed is the sedimentation velocity of the finished product. According to the feeding habits of different animals, feed with suitable sedimentation properties can be produced. Computer control of the extrusion process improves the accuracy of process adjustment and enables efficient equipment operation. The entire extrusion process control can be highly automated while ensuring feed quality.
The processing and application of puffed feed has been widely used in Europe and other countries. It started late in my country. In recent years, it has been gradually developed and applied mainly in the aquatic field, and has achieved good production benefits. Because aquatic expanded feed can be processed according to the trend characteristics of different fish species, the quality of the feed particles is better, the pollution to the water body is reduced, the nutritional value is high and the feeding method is simple. Currently, sturgeon, rainbow trout, shrimp , sea fish, tilapia and other feeds have spread all over the country. The characteristics and benefits of extruded feed are favored by the majority of farmers and have good development potential.
3. Key points of extruded feed production technology
3.1 Extruded feed production, processing and modulation Feed processing and modulation refers to the process of processing mixed feed to change the original size, nature and form of the feed raw materials to produce high nutritional value that meets the needs of breeding. The processing and modulation of feeds with good palatability can also process a variety of feeds that are not suitable for direct consumption, improve the utilization rate of feeds, and expand the sources of feed raw materials. In feed preparation, the preparation method is selected according to the type and nature of the raw material. The commonly used preparation methods include chemical, physical and biological preparation methods. The production, processing and modulation of extruded feed also depends on the modulation device. At present, a research team has invented a set of modulation device for formula feed processing, including an inclined modulation box composed of an inner box and an outer box. The inner box and the outer box There is a steam circulation mechanism between them, a feed port is provided on the top of one end of the modulation box, a feed hopper is installed at the feed port, a material distribution port is provided on the feed hopper, and an inclined vibrating screen is provided in the feed hopper. , and one end of the vibrating screen extends out of the material distributing opening to form a material distributing trough. A stirring shaft driven by a driving motor is installed in the modulating box. A stirring blade is installed on the stirring shaft. There is also a device on the inner wall of the modulating box for detecting the temperature and temperature inside the modulating box. Humidity temperature and humidity sensor probe, the bottom of the other end of the conditioning box is provided with a discharge port. The device solves the technical problems of poor steam fluidity, lack of screening and temperature and humidity control in existing feed preparation equipment, resulting in poor quality of feed preparation.
3.2 Application of twin-screw extruder in puffed feed production The key to the production process of puffed feed lies in the extrusion and puffing process, and the twin-screw extruder is an important equipment to complete this process. The screw sleeve and screw in the extruder can squeeze and shear the feed material, and extrude the die hole under high temperature and high pressure environment. When being extruded, due to the effect of internal and external pressure difference, it can realize rapid expansion. role. The puffing process is generally divided into dry and wet processing methods according to whether water needs to be added. Dry puffing does not require additional water during raw material processing. It is formed by extrusion air extrusion. The process of wet puffing is more complicated than that of dry puffing. Therefore, the mechanical structure is also more complicated than that of dry puffing machines. The raw materials need to be modulated before they can enter the puffing chamber. Additional water filling device and steam pouring device. The specific operation steps of wet extruding are as follows: first, transport the pulverized and mixed raw materials to the modulator, add a certain amount of water according to the feed production, and adjust the appropriate temperature, and then send the prepared feed into the extruding cavity, and in the extruder The pressure and temperature are gradually increased under the action of the high-speed operation of the screw in the cavity, and the pressure and temperature at the outlet of the puffing cavity reach the maximum. When the feed enters the normal pressure environment through the ring die hole, the steam escapes quickly and the pressure suddenly decreases, thus forming the feed. Violent expansion.
3.3 Batching control management system for extruded feed production With the progress of science and technology and the development of technology, the flow and process of extruded feed processing are also gradually optimized. In order to improve production efficiency, the requirements for automated production and management are getting higher and higher. The original Due to factors such as equipment aging and program lag, the production batching device can no longer meet the current highly automated production needs. Therefore, the latest ingredient control management system is gradually introduced into the application of extruded feed, and the system has been used in food, construction, chemical and other fields. The batching control management system integrates computer management technology, measurement technology, automatic control technology, and sensor technology. It has the characteristics of high control precision, fast batching speed, formula modification management, and dynamic display of process pictures. It can record and store ingredients during the batching process. Data, after completing the batching task, can also carry out list and print functions according to requirements. The system's database is open and compatible, so it is an open control method. The system can be connected to the local area network to realize integrated management and remote operation. The whole system cooperates with the motor control system, discharge mechanism, discharge mechanism, storage bin and weighing barrel, which is an important technical means to improve the production efficiency of extruded feed.
4. Summary
The use effect of extruded feed has been affirmed at home and abroad, and it is also widely used in production. The use of traditional feed processing methods has problems such as nutrient destruction, cumbersome operation, and unfavorable animal digestion. , vegetable cakes and other agricultural and sideline products are further processed, and the feed produced has the advantages of high utilization rate, hygienic and environmental protection, long shelf life, and convenient feeding. However, there are still many problems in the production of extruded feed at present, such as the high price of twin-screw extruders and easy loss during use, the mechanism of action on materials is vague, and the quality of feed is greatly affected by process parameters. In the process of technology research and development, according to different feed formulas, the optimal production conditions are found out, the extrusion technology is improved, and the dependence on the characteristics of raw materials is reduced, so as to give full play to the maximum use of the extrusion technology. Extrusion extrusion technology is likely to become the most important feed processing technology in the future.