According to a new study out from Kansas State University, corn particle size can affect digestibility and how cattle efficiently use the grain for energy and growth – meaning cattle producers will likely need to take a second look at how they are preparing their rations.
"There is a strong relationship between smaller particle size and increased digestibility of the starch (from grain)," said Chris Reinhardt, feedlot specialist for K-State Research and Extension. "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."
In a recently completed study, Reinhardt sought to find the average corn particle size Midwest feedlots use in finishing cattle diets. The idea was to learn common practices in feedlots that do not use steam-flaked corn, but instead use a form of dry processing for corn, such as dry rolling or hammer milling.
Although corn prices are cheaper now compared to recent years, Reinhardt said feedlots should still consider how particle size could affect cattle performance.
In addition to studying the average particle size, fecal samples from the finishing lots were also studied to determine how much of the grain was not digested. The more starch left in the feces, the less starch the animal actually got out of the grain.
Data collected from 34 feedlots from Kansas, Nebraska, South Dakota, Minnesota, Colorado and Iowa showed an average particle size of 4,300 microns, which means the average particle size had a diameter of 4.3 mm.
"We would call that somewhat coarse, and yet that turned out to be the average of our entire industry," Reinhardt said. "So the industry, on average, is processing corn to a coarse particle size."
He said the diet samples not only helped determine the average particle size, but the samples also were used to examine the spread of particle sizes. While the average was just more than 4,000 microns, many samples had large and fine particles in the mix.
"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.
Based on the survey, Reinhardt said he feels most feedlots that use the dry rolling method could crack their corn to a smaller particle size to improve grain digestion in cattle. The key is to get with a nutritionist and veterinarian and work together to determine an optimum finishing diet.
"Too fine (particle size) may actually cause more problems than it solves, such as acidosis and bloat," he said. "Yet we have a number of producers who are cracking the grain to a very coarse particle size and maybe leaving some money on the table. I understand that grain is relatively cheap right now, maybe historically cheap, but it won't be always, and frankly even when grain is cheap, we don't want to throw it away."
Reinhardt said this study has led to another study where he and other researchers purposely ground corn to 4,000, 3,000 and 2,000 microns and fed these samples to cattle to determine if performance—daily gain and feed efficiency—was affected by the particle size. Those results should be available soon.