Pelleting

[Asia Community Manager]

The following should be considered as general information; however, you should always seek professional advice, specific to your individual circumstances.

There is generally a good correlation between pellet durability index (PDI) values measured at the feed mill and the amount of fines delivered to the farm, meaning higher PDI usually predicts fewer fines in the delivered feed.

FEED FORMULATION ADJUSTMENTS

Add Wheat Or Wheat Gluten – gluten proteins (up to 70-80% of total proteins) in wheat and wheat by-products improve the Pellet Durability Index (PDI) primarily by acting as natural binders during the pelleting process, enhancing pellet cohesion and strength. Wheat also contains high levels of starch, which gelatinizes under heat and moisture during conditioning and pelleting. This gelatinized starch acts as a natural binder, improving pellet cohesion. (Wheat and wheat gluten may not be readily available in all regions, and particularly wheat gluten may be expensive)

Formulation Optimization – is necessary, as raw materials don’t act in isolation. Their characteristics change when combined due to physical and chemical interactions. This means you can’t simply add up the properties of individual ingredients on pellet quality; you have to consider the formulation as a whole. You can, nonetheless, estimate how a ration will react when it is pelleted, based on the binding characteristics of the ingredients as shown below:

Borregaard LignoTech has developed the Feed Pellet Quality Factor (FPQF https://www.fpqfcalculator.com/) model to predict how well a feed formulation will pellet. It assigns a Pellet Quality Factor (PQF) score to each raw material based on its effect on pellet quality and throughput. The FPQF is calculated by multiplying each ingredient’s PQF by its inclusion percentage in the feed and summing these values.

Limit Oil Content – prefer animal fats over vegetable oils to avoid soft pellets. Most animal fats, such as lard or tallow are solid at room temperature, aiding in pellet cohesion, whereas plant lipids are typically liquid at room temperature due to their high content of unsaturated fatty acids.

Limit oil added to the mixer, typically between 1-2%. Where higher levels of oil need to be added, it can be added with post-pelleting liquid application to maintain PDI.

Reduce Fiber Content – while some fiber is beneficial for structure, excessive amounts can weaken pellets.

Add Animal By-Products And Milk Products – these can act as natural binders, improving pellet cohesion.

Pellet Binders – such as lignosulfonate significantly improve PDI.

RAW MATERIAL PROCESSING

Grinding – ensure a uniform grind to increase surface area for better binding and reduce large particles that can weaken pellets. Finer particle sizes increase the surface area available for steam absorption, which enhances moisture uptake and heat transfer. This leads to more effective conditioning, as smaller particles can absorb steam more readily than larger ones.

Conditioning – helps in gelatinizing starches, which acts as a natural binding agent, improving PDI.

While higher conditioning temperatures generally improve PDI, it can also lead to the destruction of heat-sensitive nutrients like vitamins and certain amino acids, particularly lysine.

PELLETING PROCESS OPTIMIZATION

Die Size – PDI is primarily related to the die’s dimensions, such as its thickness and the length-to-diameter (L:D) ratio.

Increasing the effective thickness of the die (L) can enhance pellet durability by allowing for better compression and binding of the material. However, this may reduce production rates due to increased resistance.

A higher L:D ratio generally improves pellet quality by increasing the retention time of the material in the die, allowing for better consolidation and thus higher PDI.

While thicker dies and higher L:D ratios can improve PDI, they often decrease production efficiency. Therefore, manufacturers must balance pellet quality with production costs and capacity.

Die Speeds – lower die speeds tend to increase PDI, because slower speeds reduce the centrifugal force that can cause pellets to break as they exit the die. However, very low speeds can lead to die plugging.

HANDLING AND STORAGE

Refine Post-Pelleting Handling – most fines are generated after pelleting, especially between the cooler and load-out stages. Gentle handling of pellets, minimizing drop heights, and reducing the velocity at which pellets are moved can significantly decrease breakage.

Avoiding sharp edges and mechanical pinch points in conveying systems also helps.

Optimize Storage and Transport – pellet breakage can increase during storage, loading, unloading, and transport due to impact and segregation.

Proper silo/bin design and gentle material handling devices are essential to minimize pellet velocity and impact.

For further information:

Feed physical quality – https://aviagen.com/assets/Tech_Center/Broiler_Breeder_Tech_Articles/English/AviaTech_FeedPhysical_Oct07.pdf

How to Avoid Poor Flock Uniformity with Pellet Quality – https://www.anitox.com/news/how-to-avoid-poor-flock-uniformity-with-pellet-quality

[Muhammad Ashir Munir]

Thankyou for Detailed answer Sir!