Pellet quality is a key performance indicator in modern feed milling, influencing feed efficiency, animal performance, cost of production, and overall profitability. As a rule of thumb, for every 1% increase in fines = 1% financial loss on the tonnages delivered. Among the many factors that determine pellet integrity, moisture content is one of the most critical.
When moisture levels fall below optimal ranges during conditioning and pelleting, a series of mechanical, nutritional, and operational issues arise. Understanding these challenges and adopting proper moisture-management strategies can significantly enhance pellet durability, reduce fines, and improve mill efficiency.
Why moisture matters in pelleting
Moisture acts as both a plasticiser and lubricant in the pelleting process. In the conditioner, steam adds heat and moisture to the feed mash, softening particles and promoting starch gelatinisation. This improves adhesion between ingredients as they are compressed through the die. When moisture is too low, the mash cannot achieve the physical transformation needed for strong, durable pellets. Poor water activity also reduces heat-transfer efficiency, making it harder to achieve target temperatures for conditioning.
Common pellet quality problems caused by low moisture
Weak pellets and low Pellet Durability Index (PDI)
One of the most immediate effects of low moisture content is a reduction in pellet strength. Without adequate moisture, the mash remains rigid and resists compaction, leading to poorly formed pellets. These pellets tend to crumble easily during cooling, conveying, and bagging. A low PDI results in higher fines, increased feed wastage, and inconsistent nutrient intake by the animals.
Excessive dust and fines
Pellets produced from dry mash are brittle. As they collide within the cooler or are transported via augers and conveyors, they break down into fines. High fines not only reduce the value of the feed but also affect animal performance. Broilers, for example, prefer intact pellets and will sort feed, leaving fines behind. This results in unbalanced nutrient consumption.
Reduced die throughput and higher energy use
Low moisture increases friction between mash and die surfaces. The pellet mill motor must work harder to compress dry particles, resulting in lower production rates and higher energy consumption. Mills typically experience between a 10-30% reduction in throughput when moisture levels are below optimal. In extreme cases, the die may choke or glaze over, requiring shutdown and cleaning.
Poor starch gelatinisation and binding
Moisture is essential for gelatinising starch during conditioning. Gelatinised starch acts as a natural binder, strengthening pellets and improving durability. Insufficient moisture reduces the extent of gelatinisation, resulting in structurally weak pellets. Nutrient digestibility may also decrease, particularly in high-starch diets such as those used in poultry and aquaculture.
Accelerated wear on dies and rollers
Friction caused by dry mash also leads to increased mechanical wear. Rollers and dies deteriorate faster, shortening equipment lifespan and raising maintenance costs. Die holes glaze more rapidly, further reducing pellet quality and consistency.
How the addition of moisture improves pellet quality
Adding moisture – either through high-quality steam or approved liquid additives – can resolve many of the issues caused by overly dry mash. The goal is to achieve optimal moisture levels entering the die (typically 14-16.5%) and appropriate levels in cooled pellets (10.5-12%).
Improved conditioning and heat transfer
The purpose of conditioning is to increase feed mash temperature and moisture content to improve the pelleting process. Key parameters for conditioning are temperature (80-90°C) and moisture (16-18%). Every 15-17°C increase in conditioning equates to 1% moisture content rise.
To achieve these desired parameters, it is essential to maintain proper moisture content in the feed mash before conditioning. Keep in mind that the moisture level in the mash should not exceed 14%. Test mash feed for “baling” after the mixer as you increase the moisture level and reduce moisture if present.
Understand the capabilities and limitations of the pellet cooling system and be aware of water activity levels.
Enhanced lubrication during pelleting
With adequate moisture, the mash flows smoothly through the die, reducing friction and pressure. This lowers motor amperage, increases throughput, and reduces wear on mechanical parts.
Stronger pellets with higher PDI
Moisture facilitates the chemical and physical transformations required for strong pellet binding. This results in pellets with improved integrity, fewer fines, and better resistance to mechanical stress. Higher PDI directly improves feed conversion ratios by ensuring animals consume nutrients uniformly.
Reduced energy costs
Good lubrication and lower friction translate to decreased electricity usage per tonne of feed. Mills operating with optimal moisture often report energy savings of 5-15%. Using a good moisture management product will further reduce the cost of energy used to pellet feed.
Use of moisture-enhancing additives
Beyond steam, feed mills can incorporate binders or moisture-retention agents such as moisture management products. Glycerol esters of propionic acid and surfactants (SmartMoisture) is a new generation product that help retain water in the pellet, prevent overdying in the cooler, and stabilize the final moisture level.
The graph below shows pellet durability improvements when SmartMoisture is used to improve moisture content in mash feed before conditioning. The pellet durability is largely unaffected by SmartMoisture when PDI index is high (>90%). In feeds with poor PDI (<75%), there is a significant improvement when moisture is added by using SmartMoisture.
Conclusion
Low moisture content is a common but often overlooked cause of poor pellet quality. Problems such as weak pellets, high fines, low throughput, and increased equipment wear all stem from inadequate moisture during the pelleting process.
By optimising conditioning, improving steam quality, and using moisture-enhancing additives, when necessary, feed mills can significantly improve pellet strength, reduce production costs, and enhance overall efficiency. Effective moisture management is therefore not just a technical consideration but a vital component of producing high-quality feed that supports both mill profitability and animal performance.
