While a lot of work is done on choosing raw materials and optimizing formulations for making animal feed, the importance of pellet quality is a vital aspect for optimum animal performance and reducing feed wastage. The Feed Pellet Quality Factor (FPQF), which indicates how well a feed formulation is likely to pellet is a proprietary information validated over a period of time and now available to the feed industry. It is well established that high quality pellets can withstand repeated handling and can remain intact during bagging, transportation, storage, and moving in feed lines without excessive breakage or generation of fine particles. The present article discusses how feed pellet quality is impacted by raw materials changes and also gives some guidelines to minimize variability of feed pellet quality.
Pellet quality & FCR
Good quality pellets result in homogenous feed, reduced wastage, reduced segregation, improved palatability and allows animals to consume the bulk of their meals in less time. Pellets high in fines and with a low pellet durability index (PDI) usually result in a higher FCR (Table 1 Ref: J. Quentin, et. al.m, J. Appl. Poul. Res. 2004. 13:540-548)
Factors affecting pellet quality:
In today’s dynamic world, Nutritionists face the challenge of formulating feeds using available raw materials at the lowest possible cost while meeting the feed specifications, while the production managers face the challenge of producing the good quality pellets from these ingredients at the optimum mill setting. Pellet quality is proportionally dependent on several factors, with diet / feed formulation being the most important.
Diet or Feed formulation
Pellet durability may be improved by manipulation of the formulation (raw materials and feed additives). Raw materials affect pellet quality depending on their “binding properties” and its proportion in the formulation. Unfortunately, corn-soy diets are not the ideal diets to achieve good pellet quality. Dietary inclusion of wheat grain or wheat by-products can increase PDI, because of the high protein (gluten) and hemi-cellulose content of wheat in comparison to corn or corn co-products.
From our experience we know that starch gelatinization is the most important factor for achieving the desired pellet quality. We also observe that the temperature, moisture and conditioning time under normal pelleting conditions in Asia are not enough to get the desired level of gelatinization of natural raw materials. Also, recent reports indicate that the positive impact of protein on pellet quality is equally important as that of starch.
Dietary inclusion of oil has a positive effect on animal growth but an adverse effect on pellet quality. This is attributed to the coating effect of oil to the feed particles, which prevents their penetration by steam. This has an impact on digestibility. Oil also reduces the friction generated between die and the feed particles, which subsequently reduces the compression pressure required to produce good pellets and also decreases the starch gelatinization rate. Inclusion of natural pelleting aids can help overcome these bottlenecks and improve pellet quality, increase pellet throughput and lower the power consumption.
High starch containing raw materials like wheat generally contribute to good quality pellets. Feed stuffs like skim milk powder and tapioca also have a positive effect on pellet quality but usually find challenges in throughput and results in choking if the pellet mill settings are not correct. Addition of oil would improve the throughput but has limitations and will usually deteriorate pellet quality at high inclusion levels. Pelleting aids have been used to improved pellet quality and throughput when needed.
Calculating the FPQF
The FPQF is a tool developed by Borregaard Lignotech to be used as a guideline to predict the pellet quality of a feed formulation. Each feed ingredient has a pellet quality factor (PQF). The PQF has a score from 0 to 10, where 0 predicts poor pellet quality and 10 good pellet quality. The FPQF of virtually all raw materials fall between 0 and 10, the exceptions are fat (vegetable oil) at -40 and Borregaard LignoTech’s range of pelleting aids from 25 to 50. As these raw materials affect pellet quality significantly at very low inclusion rates, they have been given values outside the normal scale.
We can estimate the FPQF for each ingredient by multiplying the PQF by the % of inclusion of the feed ingredient in the formula (Figure 2). The overall FPQF equals the sum of the FPQF of all ingredients used in the formulation.
In order to enable feed producers to calculate the FPQF of their feeds, an online version of the Feed Pellet Quality Factor calculator is launched*. Simply register to get free access, type the name of the formulation, then click the create button to start choosing ingredients and add the % inclusion for each ingredient in your feed formulation. Once the recipe is complete, i.e. you have reached 100%, the Feed Pellet Quality Factor of the formulation is calculated and shown. It will also show the bulk density of the formulation. The formulations and entries have privacy protection and can be accessed by the registered users only.
Borregaard LignoTech sees 4.7 as a ‘reference’ FPQF-value.
FPQF value below 4.7 suggests pellet quality problems wherein production parameters may need to be adjusted to achieve desired pellet quality and consider using a natural pelleting aid.
FPQF higher than 4.7 indicates that the pellet quality would most likely be good but production rate can be increased or maximized.
The FPQF values listed are based on vast experience of the company and practical observations made by the Technical team over many decades. However, feed raw material quality is subject to geographical origin, variety of seed, seasonality etc. and may vary from time to time. If you see a change in your production without a formulation change it may be that the specification of one of your raw materials has changed. FPQF results also depend on feedmill factors as well as raw material factors. There is no such thing as a standard feedmill, so the same raw material will behave differently in separate mills under varying processing conditions.
Troubleshooting during Pelleting
Even though you have a high FPQF but still not getting the desired pellet quality, it is therefore important to look into the other factors affecting pellet quality (figure1):
Conditioning: Different formulations require different conditioning parameters. It is important to identify the ideal meal temperature, steam pressure, and conditioning time. Orientation of the paddles in the barrels is also important to allow better incorporation of the steam in the meal
Die specification: As a general rule the thicker the die and the smaller the pellet size the better the pellet quality. Pellet size is largely determined by the species to which it has to be fed.
Particle size: As a general rule, the finer the grind the better the pellet quality as there is a larger surface area for the raw materials to be conditioned. However this will lead to higher grinding costs. The grist spectrum should also be analyzed to determine if finer grind is needed especially for the raw materials which are high in starch, depending upon the type of animal species to which it is to be fed.
Cooling and drying: Removing excess heat and moisture after pelleting is ideal to prevent mold growth. Excess free moisture inside the pellets will travel within the pellets, which would eventually lead to pellet breakage. Test for feed moisture content (ideal 10-12%) and water activity (ideal Aw < 0.6).
Although a high FPQF indicates that the outcome would be a good PDI, this is not always the case. In such instances along with adding a reliable pelleting aid, having a look at the other pelleting parameters can go a long way in achieving optimum pellet quality and efficiency.
* FPQF calculator can be accessed at www.fpqfcalculator.com
For further information, author can be contacted at firstname.lastname@example.org
by Ramesh Subramonian, Borregaard SEA