There are several advantages of eating pellets for broilers compared to eating powders, the main one being that it can improve the performance of broilers. Compared to broilers fed meal, broilers fed pellets took less time to eat and digest and had lower body maintenance requirements.
 
1. The quality of pellets
High-quality pellets can be defined as feed pellets that can withstand repeated operations, such as bagging, transportation, storage, and feed line conveying without excessive breakage or production of too many fine particles. Pellet quality is usually expressed in terms of the Pellet Durability Index (PDI) and can be measured in a tumble jar: a sample of the particles to be tested is first sieved to remove fines and then tumbled in a tumble jar for a certain period of time. The tumbled sample is sieved to remove fines, from which the weight of the intact particles can be obtained.
 
2. The formula for calculating PDI is as follows:
PDI = weight of complete particles after tumbling / weight of complete particles before tumbling × 100
Some other equipment can also be used to measure the durability of particles, such as Holman particle detector, wood detector, etc.
 
3 Factors affecting the quality of feed pellets
3.1 Feed formula
Certain feed ingredients are beneficial for improving pellet quality, while others may be detrimental. Unfortunately, corn-soybean meal-based diets are not ideal for optimal pellet quality. Since wheat contains high levels of protein (gluten) and hemicellulose compared to corn or corn by-products, diets supplemented with wheat kernels or wheat by-products (wheat mid-gluten, wheat gluten) will have higher kernels after pelleting Durability. Likewise, partial replacement of corn in the diet with oats can improve the quality of the feed pellets. We can rank the beneficial effects of feed grains on feed pellet quality, from best to worst: oats, wheat, barley, corn, sorghum.
It has long been known that starch and its gelatinization are the most important factors in achieving optimum quality of feed pellets. However, recent reports suggest that the beneficial effect of protein on feed pellet quality is far more important than that of starch.
The addition of oil to the diet can adversely affect the quality of the feed pellets. This is because the oil will surround the feed pellets, which will hinder the penetration of steam into the pellets. In addition, the oil will reduce the friction between the ring die and the feed pellets, which will reduce the rate of starch gelatinization.
Adding binders [e.g. water (the simplest binders), lignosulfonates, hemicellulose extracts, gelatin, etc.] and/or surfactants to the diet can improve the quality and yield of feed pellets, and Energy consumption can be reduced.
Feed Pellet Quality Factor (FPQF) is a tool that can be used to predict the quality of pellets in feed formulations.
Estimating the FPQF of a certain feed formula: Each feed ingredient has its own unique Pellet Quality Factor (PQF). The score of PQF ranges from 0 to 10, where 0 indicates poor quality of feed pellets and 10 indicates excellent quality of feed pellets. We can estimate the FPQF of each ingredient by multiplying its PQF value by its percentage in the recipe. The FPQF value of a feed formulation is equal to the sum of the FPQFs of all ingredients used in it. In general, a feed formulation with an FPQF value below 4.7 indicates poor pellet quality, while above 4.7 indicates good feed quality.

3.2 Particle size of feed ingredients
Although some researchers have doubts about this, most people still believe that reducing the particle size of feed ingredients is beneficial to improve the particle quality of the feed. However, we do not recommend excessive shredding to avoid wasting energy and reducing productivity, and doing so is detrimental to broiler gizzard development. On the other hand, coarse grinding reduces the breakdown of feed pellets and reduces starch gelatinization (a high degree of gelatinization is required to produce good quality feed pellets).

3.3 Steam conditioning
As the powder passes through the conditioner, it is exposed to high pressure steam. This steam provides the heat and moisture needed to gelatinize the starch, bond the pellets to each other, leave the feed in a semi-digested state, and kill pathogens in the feed. The steam temperature and the time of the meal in the conditioner have a great influence on the durability of the feed pellets. Conditioning feed at 80 °C is sufficient to produce high quality feed pellets. To produce tolerant feed pellets, the minimum residence time of the powder in the conditioning cylinder is 30 s. Long-term use of a conditioner (the feed can stay in the conditioner for 3 to 4 minutes) can be used to improve the viscosity of feed pellets.

3.4 Ring die/roller specifications
Pellets are produced by pressing hot powder into a ring die by pressing rollers. A thicker ring die (longer ring die channel) is beneficial for improving the durability of the feed pellets, as this increases the friction time between the feed pellets and the ring die wall, resulting in more complete starch gelatinization. Most of the starch gelatinization occurs as the feed passes through the ring die. Similar results can be obtained by using a small aperture ring die. This means that a 60 mm thick ring die is better than a 50 mm or 40 mm thick ring die, and a 3 mm ring die aperture is better than a 5 mm ring die aperture. However, ring dies that are too thick or too small have a negative impact on particle yield. In addition, increasing the distance between the press roller and the ring die from 0.1 mm to 2 mm improves the durability of the feed pellets.

3.5 Cooler
When leaving the pellet mill, the temperature of the feed pellets is 70 ℃ ~ 90 ℃ and the humidity is 15% ~ 17%. Feed pellets require moderate cooling (using a steam cooler) to reduce the pellet temperature to about 8°C above ambient temperature and to bring its humidity down to 12%. The type of cooler can be horizontal or vertical. Rapid cooling causes the surface of the feed pellet to lose more moisture and heat than the interior of the pellet, making the pellet brittle. On the other hand, prolonged cooling can make feed pellets too dry, which can be prone to wear and poor palatability.