Effect of Ground Corn Fractionation on Flowability

Particle size reduction is an important component of feed manufacturing that impacts pellet quality, feed flowability, and animal performance. However, reducing particle size too fine often results in reduced flowability of the ground corn and finished feed, which creates potential handling and storage concerns at the feed mill and farm. The objective of this experiment was to determine how fractionation affected flowability of ground corn. Whole corn was received from a single source and ground to achieve 3 target particle sizes, 400, 500, and 600 µm with actual results of 469, 560, and 614 µm. Each target particle size was fractionated into three segments: fine (< 282 µm), medium (> 282 µm and < 630 µm), and coarse (> 630 µm) particles using a vibratory separator (model LS18SP3, SWECO, Florence, Ky.). Within particle size treatment, the percentage of sample obtained for each fraction was: 400 µm: 4.9%, 34.2%, and 60.9% for fine, medium, and coarse, respectively; 500 µm: 1.9%, 31.3%, and 66.9% for fine, medium, and coarse, respectively; and 600 µm: 1.0%, 24.4%, and 74.7% for fine, medium, and coarse, respectively. When the fractions were separated, their particle sizes were: 400 µm: 94, 269, and 744 µm for fine, medium, and coarse, respectively; 500 µm: 96, 253, and 815 µm for fine, medium, and coarse, respectively; and 600 µm: 99, 220, and 898 µm for fine, medium, and coarse, respectively. Fractionated samples were analyzed for multiple flowability characteristics, including: angle of repose, critical orifice diameter, composite flow index (CFI), bulk density, and compressibility. Treatments were arranged in a nested model with three replicates per treatment. Data were analyzed using the GLIMMIX procedure of SAS. When fraction was nested within particle size for each treatment, the fine fraction (< 282 µm) of the 400 µm corn had the poorest CFI (P < 0.05). Whereas the coarse fraction (> 630 µm) of the 600 µm corn had the best CFI. The nutrient content of the fractions was greatest in the medium fraction (> 282 µm and < 630 µm) for crude protein, fat, and acid detergent fiber (ADF). In conclusion, reducing particle size resulted in the ground corn having poorer flowability characteristics, caused predominantly by particles that passed through a 282 µm screen. Based on this data, producers may potentially grind corn to a lower particle size while maintaining flowability if fine particles (< 282 µm) are removed.