In the world of poultry feed production, achieving the perfect particle size for corn is crucial to ensure the health and productivity of flocks. Properly ground corn has become a fundamental ingredient, providing essential nutrients and energy for growth. Feed mill managers must know how to determine the optimal particle size when setting a grinder to produce high-quality feed efficiently and economically.

Understanding Poultry Nutrition

Corn is a primary component of poultry feed due to its high energy content and digestibility. For maximum benefit, corn must be ground to an appropriate particle size. Poultry, whether broilers, layers or turkeys, have specific digestive systems optimized for processing grains like corn. Digestion and absorption of nutrients are optimized when corn is ground to the correct particle size, which leads to better growth, egg production and overall flock health.

Grinding Equipment Matters

Achieving the right corn particle size hinges on the capabilities and settings of grinding equipment. Feed mill managers should know their grinder’s specifications, as different grinder types, i.e., hammermills or roller mills, have distinct capabilities when it comes to particle size reduction.

Hammermills reduce particle size via the impact of rotating hammers connecting with the material, which remains in the grinding chamber until it has reached the minimum orifice diameter required to exit the screen. Screen size, number of hammers and speed of rotation can all contribute to particle size. This process produces a less uniform size with a wider distribution, measured as increased standard deviation.

In comparison, the roller mill uses shear force to reduce particle size as material passes through sets of corrugated roll pairs. Clearance between the grinding surfaces of the rolls, corrugation number and sharpness can all impact achievable size. While this grinding action produces a more consistent, uniform distribution of particle, the feasibility of achieving smaller sizes (<600 micron) may depend on the number of roll pairs in the machine.

Measuring Particle Size

Accurate measurement is crucial to achieve desired results. Several methods exist to assess particle size, though variations within method can influence the results.

Sieve analysis is the most common method of measurement. It involves passing a sample of ground material through a set of progressively finer sieves. Particle size and distribution are then calculated based on the weight retained on each sieve. This method allows for several variations including the use of sieve agitators, inclusion of dispersing agent and sieve time, which can have a large impact on final measurement. The most significant impact occurs with the inclusion of a dispersing agent, which can lower the particle size result by an estimated 80-100 microns.

While achieving the lowest possible particle size measurement should be the goal as it indicates the greatest accuracy, many producers still choose to exclude dispersing agent from analysis. In many cases, these producers may develop their own sieve method aimed to reduce time and effort associated with the analysis. These unapproved variations only serve to further compromise the accuracy of the results. Thus, it is important to note what methodology results are based on and ensure it correlates well with the standard sieve method.

Alternative methods like microscopic analysis can provide detailed information about the particle shape and size but are less practical for routine quality control. Near infrared reflectance spectroscopy (NIR) is a more attractive option. With NIR, particle size can be measured based on light refraction, offering an accurate and efficient analysis through a proven, less time-consuming methodology.

Corn Particle Size and Animal Performance

Smaller particles, though more costly, offer advantages including increased surface area for digestive enzymes to access and break down nutrients, improved mixing uniformity and pellet quality, and minimized segregation during handling. But physiological differences of birds must also be considered to determine optimal particle size.

Birds have relatively short gastrointestinal tracts compared to other animals and rely on their gizzard to compensate. A strong, well-developed gizzard ensures proper retention time of the feed in the GI tract through reverse peristalsis, improving digestion and nutrient absorption. This can have greater implication on gut health by limiting the availability of nutrients in the lower gut to pathogenic bacteria, thus reducing the risk of enteric disease. Proper reverse peristalsis can also ensure optimal pH of the gizzard via HCl secretion from the proventriculus, which may aid further in reducing bacterial transfer into the gut.

Xu et al. (2015) suggested coarse corn mixed with fine corn can stimulate the gizzard and slow passage rate while increasing digestibility with finer particles. Xu replaced 50% of the fine corn (294 microns) in a broiler diet with coarse corn (1359 microns) to increase total mash particle size from 432 to 640 microns in grower and 389 to 651 microns in finisher pre-pelleting. Results showed heavier gizzards, improved FCR and increased nitrogen and energy digestibility at 49 days of age.

Xu also cautioned larger particle sizes should be limited in early starter phases as younger birds may lack the ability to consume and grind large particles. This sentiment was echoed by Nir et al. (1994), who found broilers fed a corn particle size of 897 microns had increased body weight gain with lower FCR when compared to chicks fed 2,010-micron corn from 1 to 7 days. Based on this, it may be prudent to reserve larger particle size for later stages with a more mature bird. Rubio (2020), however, advises when there is intent to feed coarser particles in subsequent phases, gizzard development should be stimulated early in preparation.

Conclusion

Ideal particle size determination for corn in poultry diets is multifaceted. One needs to consider not only the capabilities of their grinding equipment, but also the age of the birds and gizzard development. Once determined, quality control procedures should be implemented to sample and measure particle size periodically.

Contact author, Caitlin Evans (Technical Support Services Manager) of AB Vista for more information at [email protected].

References

Available upon request