According to a study by Kansas State University, not all corn is created equal when it comes to how particle size affects feedlot cattle’s ability to digest corn and use it for energy and growth.

Chris Reinhardt, K-State Research and Extension feedlot specialist, says there is a strong relationship between smaller particle size and increased digestibility of the starch from grain.

“Regardless of what kind of grain, we feed it for the starch component. The more starch we can get digested, whether that be in the rumen or downstream from the rumen, improves the return on the investment in that grain,” Reinhardt explains.

For the study, data was collected at 34 feedlots in Kansas, Nebraska, South Dakota, Minnesota, Colorado and Iowa. Reinhardt’s goal was to find the average corn particle size in finishing diets. He says the idea was to learn common practices in feedlots that use processes like dry rolling or hammer milling instead of steam-flaked corn. The study also looked at fecal samples to determine how much of the grain was digested – the more starch leftover, the less the animal got out of the grain.

Based on the data collected, the average particle size was 4,300 microns, or about 4.3 mm in diameter, a size Reinhardt says is considered somewhat coarse. Many samples had much finer particles in the mix, however, he says.

“Two of the feedlots used not dry rolling but dry hammer milling, which creates a much finer, smaller particle size and also a large amount of the fine particles,” Reinhardt said.

Overall, Reinhardt says most feedlots that use the dry rolling method could crack corn into smaller particle size to improve digestion. Too fine, however, he notes could cause more problems, including acidosis and bloat. Too coarse, and feedlots “may be leaving money on the table.” That’s another reason, he says, feedlots need to enlist help from a nutritionist and veterinarian to determine the optimum finishing diet for the cattle.

This study led to another study, which is currently underway, in which researchers ground corn to 4,000, 3,000 and 2,000 microns and fed to cattle to determine if performance (daily gain and feed efficiency) is affected by particle size of the corn. Reinhardt says the results should be available soon.