Analysis of factors affecting the quality of pellet feed


Pellet feed can improve the growth rate and feed utilization of livestock and poultry, and its processing can also eliminate anti-nutrients, thereby improving the digestibility of nutrients. This article specifically analyzes various factors that affect the quality of pellet feed, in order to benefit the production of pellet feed.

1 Feed ingredient factors

1.1 Raw materials

The quality of raw materials has a great influence on the quality of feed. The characteristics of raw materials mostly depend on the feed formula technology. The formula contains energy feed, protein feed, mineral feed and additive premixed feed, respectively: 60% ~ 70%, 20% ~ 25%, 3% ~ 5%, 1% ~2%. Energy feed and protein feed are the main components and the main factors affecting feed quality. Our country has a vast territory, complex terrain, various soil types, and large climate differences. Even the same feed has different nutritional content due to different origins, varieties, processing methods, and quality levels. Just like corn, the content of crude protein, crude fiber and crude fat in corn varies greatly depending on its origin, variety and grade. It is necessary to choose products with high potency, good stability, and dosage forms that meet the requirements for compound feed production. Therefore, when designing the formula, you must pay attention to the value of the nutrient content of the raw materials, and try to make the value of the nutrient content of the raw materials relatively reasonable or close, so that the formulation The feed can fully meet the physiological needs of animals, and can produce products that meet product quality standards. At the same time, it does not waste feed raw materials.

1.2 Protein content

Protein content is an important factor in determining the quality of pellet feed. Generally speaking, when the protein content in the formula is higher, it is easier to pellet and the pellet quality is better, because the plasticity of protein increases after being heated, which increases the pelleting yield and good quality. But when the protein content in the formula is too high, the granulation effect decreases. 30% of the concentrated feed for laying hens (excluding energy feed) is pelleted, and its protein content is more than 35%. Since the starch content in this formula is reduced and the crude fiber content is more than 12%, its ability to absorb steam is seriously reduced. If the feed conditioning temperature is only 50 to 60°C, the quality of the pellets will also be seriously reduced.

1.3 Cellulose content

The cellulose content in the feed should not exceed 10%, because the fiber itself has poor cohesion. If the content is high, the binding force between feed particles will decrease, and it will also affect the ability of the feed to absorb steam, thereby reducing the hardness, molding rate and The output is reduced and the granulation equipment is seriously worn.

1.4 Fat content

If an appropriate amount of fat is added to the feed, the fluidity of the feed through the die hole will be good, the friction resistance will be reduced, the feed will be easy to shape, and the ring die of the granulator will have less wear, low energy consumption, and good pellet quality. However, the fat content added to the feed will If it is too high, the quality of the pellets will decrease, because oil can reduce the binding force between feed particles, making the pellets easily broken and difficult to store. When excess fat is needed in the feed, it can be added by spraying after pelleting.

1.5 starch

Starch is easy to gelatinize under high temperature and high moisture conditions and can play a natural binding role. However, under low temperature and low moisture conditions, starch not only fails to gelatinize but also produces brittle particles, which affects the quality of the particles.

1.6 Moisture content

Generally speaking, when the moisture content of feed before conditioning is less than 12.5%, its ability to absorb steam is strong, the conditioning temperature is high, and the pellet quality is good. According to many years of experience, the effect is best when the moisture content of powdered feed is 15.5% to 17% after conditioning. According to general rules, for every 10°C increase in temperature during conditioning of powdered feed, the moisture content increases by approximately 0.6%, and the temperature for starch gelatinization is required to be 80°C. Therefore, the moisture content of starch feed before conditioning should not be too high, otherwise it will The ability to absorb steam decreases, the conditioning temperature of powdered feed decreases, the degree of starch gelatinization and protein denaturation decreases, the binding force between feed particles decreases, and the quality of the particles decreases. If the moisture content of the material is too high, it will be difficult to temper and it will easily cause the material to slip between the inner wall of the ring die and the pressure roller, causing the ring die to be clogged and the produced particles to be mixed with more powder. Generally, the moisture content of the material before conditioning is required to be 13%. the following. For very dry materials such as beer yeast, sufficient unbound water should be added before granulation to obtain good granule durability.

2 Conditioning factors

Conditioning is to pass the feed through a conditioner with high temperature and high pressure steam to denature the protein contained in the feed, increase the degree of starch gelatinization, change the physical and chemical properties of the feed, and promote the conversion of starch into soluble carbohydrates, making it more beneficial Animal digestion and absorption. The amount of steam added during conditioning is related to the moisture of the raw materials and the type of feed produced. The effect of powdered feed is better when the moisture after conditioning is 15.5% to 17%. If the moisture after conditioning exceeds 17%, the feed particles will be combined. When the force decreases, the material will slip and cannot be pressed into the die hole, resulting in a large amount of granular powder and easily causing machine blockage. When adding raw materials such as molasses and urea, do not add too much steam during the tempering process, because too much steam will increase the temperature and cause problems such as cracks and coking. The gelatinization of starch can improve the quality of pellet feed and improve the digestibility of feed. The temperature for starch gelatinization is required to be around 80°C. Therefore, the moisture content of starch feed should not be too high before conditioning, otherwise the ability to absorb steam will decrease. Generally, starch in the pelleting process The degree of gelatinization can only reach about 20%. To further gelatinize, the temperature and steam pressure must be increased. In particular, aquatic feed requires a certain stability in water, and the pelleting temperature is 85 to 90°C. Different formulas have corresponding steam parameters, and the corresponding steam parameters should be adopted according to the specific formula.

3 operating factors

The operating factors mainly refer to the adjustment of the gap between the pressure roller and the ring die, the adjustment of the cutter, and the belt tension, including steam control, granulator operating skills, etc.

3.1 Adjustment of the gap between the pressure roller and the ring die

Before the production of the pellet machine, the pressure roller must first be adjusted. Whether the gap between the pressure roller and the ring die is adjusted correctly will have a great impact on the quality of the pellet material, the granulation efficiency, and the life of the ring die and the pressure roller. If the gap is too small, metal and metal will rub against each other, destroying the pressing angle of the die hole, making it difficult for materials to enter the die hole, reducing output, and even clogging. If the pressure roller is adjusted too far away from the ring die, it will cause the pressure roller to slip and overheat, the material to coke, the material cannot be absorbed, the mold will be blocked, and even the conditioner will be blocked, affecting the granulation output. The best position of the pressure roller and the ring die is so that when the ring die rotates slowly, its most protruding point just touches the pressure roller slightly, and then the pressure roller is slightly rotated counterclockwise, so that the pressure roller appears to rotate during normal operation. Non-transfer effect.

3.2 Cutter adjustment

The cutter is used to control the particle length. The number of cutters is usually determined by the number of pressure rollers in the granulator. Generally, the number of cutters in a granulator depends on the number of pressure rollers it has. Every time the ring die rotates once, a certain amount of material is extruded and then cut off by the corresponding cutter. If the output is constant, the granules produced by a granulator with three cutters are shorter than those produced by a granulator with two cutters. In other words, a three-roller granulator is more conducive to controlling the length of the granules than a two-roller granulator, especially The advantage is particularly obvious when producing aquatic feed with small particle size. The sharpness of the cutter also has a certain impact on the quality of the particles. Generally, the sharper the cutter, the smoother the cut will be. Of course, the sharpness of the cutting edge also has a reasonable limit. Once this limit is reached, it is difficult to improve it. By changing the inclination angle α of the cutter, the cut of the pellet material is cleaner. Usually the inclination angle α is suitable between 30° and 45°.

3.3 Belt adjustment

For belt-driven granulators, pay attention to the tension of the belt. If the belt is too loose, it will easily slip, increase energy loss, and easily burn the belt. If it is too tight, the current will increase, damaging the motor and the rotor of the granulator. Especially for granulators driven by two motors, the belts of the two motors should be as consistent as possible to ensure that the current error of the two motors is within 5%, ensuring uniform stress on the rotor and improving operational stability.

3.4 Cooling and drying

The cooling and drying process directly affects the quality of the finished pellet feed. The cooling equipment for pellet feed in production generally chooses counter-current and convection coolers. After cooling, the temperature of pellet feed is no higher than the ambient temperature 5℃, and the moisture is less than 13%. Too high temperature and too high moisture are not conducive to storage and are prone to mold. Change, high powder content and poor hardness. The cooling effect is related to the ventilation volume, time and speed. If the time is too short, the cooling will be insufficient. In the process design, it is necessary to ensure that the pellet feed stays in the cooler for a certain period of time, so as to ensure that the inside and outside of the pellets are fully dried. Otherwise, it is easy to cause the surface of the hot pellets to cool quickly, and the heat and moisture contained inside are not sucked out, causing the pellets to break and affecting the pellets. Surface quality and molding rate. Generally, the wind speed in cooling air ducts is controlled at 15-20m/s. Excessive wind speed can easily suck away materials, causing pipeline obstruction and difficulty in recycling.

3.5 Hierarchical screening

After the pellet feed is tempered, granulated and cooled, there will be about 5% powder, large particles and small particles. These materials enter the classification screen for screening. The qualified pellets enter the buffer bin, and the powder and unqualified particles The material enters the storage silo through the elevator, and undergoes conditioning, granulation and cooling again before being graded and screened. For different types of feed, the mesh sizes of the upper and lower grading screens are different. This requires feed producers to fully consider these factors before pelleting, and install and replace the grading screens in strict accordance with industry standards to ensure the quality of the pellet feed. Finished product quality.

4 Conclusion

The quality of pellet feed is the combined effect of the above factors. Therefore, only by comprehensively considering the above influencing factors can the pellet feed have good quality and ensure the development of animal husbandry in a high-quality, efficient and healthy direction.

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