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Effect of feed formula and raw material quality on feed quality
Feed formulation and the quality of raw materials significantly influence the quality of pelleted feed. The formula typically includes energy feed (60%–70%), protein feed (20%–25%), mineral feed (3%–5%), and additive premix (1%–2%). Energy and protein feeds are the primary components that directly affect pellet quality.
**1. Diversity of Raw Materials**
Today, many feed manufacturers use alternative ingredients to reduce costs, such as wheat bran, rice bran, DDG, brewer’s grains, corn gluten meal, bacterial protein, yeast, rapeseed meal, cottonseed meal, blood meal, meat and bone meal, and silkworm pupa powder. However, these alternatives often vary in quality, which can reduce the ability of the material to absorb steam. This leads to loose particles, poor surface appearance, low hardness, and a high rate of crumbling.
To improve pellet quality, binding agents like wheat flour, soybean meal, or bentonite are often added. Depending on the specific conditions, using the right amount of wheat or soybean meal is preferable because they contain gluten and soluble fiber, which help absorb steam more effectively and enhance pellet quality.
**2. Protein Quality**
Protein content plays a key role in determining pellet quality. Higher protein levels generally improve granulation and result in better-quality pellets because proteins become more plastic and viscous when heated. However, if the protein content is too high, it may negatively impact the granulation process. For example, in 1999, our factory had to process a concentrate with over 35% crude protein, but due to low starch and high fiber content, the steam absorption was poor, resulting in lower pellet quality.
**3. Cellulose Content**
The crude fiber content in feed should not exceed 10%. High fiber levels reduce the adhesion between particles and impair the feed's ability to absorb steam. This leads to weaker pellets, lower production efficiency, and increased wear on the granulating equipment.
**4. Fat Content**
Adding an appropriate amount of fat improves the flowability of the feed through the die, reduces friction, and enhances pellet formation. It also lowers energy consumption and minimizes die wear. However, excessive fat can weaken the binding force between particles, leading to broken pellets and storage issues. If extra fat is needed, it is recommended to apply it after the pelleting process.
**5. Moisture Content**
Moisture before conditioning is crucial. When moisture is below 12.5%, steam absorption is strong, and the conditioning temperature is higher, resulting in better pellet quality. Ideally, the moisture content of the powdered feed after conditioning should be between 15.5% and 17%. Starch gelatinization occurs at around 80°C, so maintaining proper moisture levels is essential. Too much moisture can reduce steam absorption and lower pellet quality.
In recent years, new corn has been challenging to steam during conditioning, leading to high power consumption, low productivity, and poor pellet hardness. To address this, we temporarily store the feed in the intermediate warehouse for 16–24 hours, allowing better moisture distribution before pelleting. This method improved steam absorption and maintained a conditioning temperature above 70°C.
**6. Hygroscopicity of Raw Materials**
Hygroscopic materials, such as citric acid whey powder or milk replacer, can severely reduce the flowability of the feed if stored for long periods. These materials tend to clump and become difficult to process, especially during high-temperature granulation. This results in low temperatures and poor pellet quality. In such cases, rapid steam injection methods are necessary to ensure good granulation performance.