Particle Size Of Swine Diets

Michael Edmonds, Ph.D., Vice President, Swine Nutrition

We have generally recommended a particle size of 750 to 850 microns in growing-finishing diets.  Compared to a coarse grind (i.e., 1000 to 1200 microns), the finer grinds do require checking feeders more often because there can be some bridging of feed in the feeders.

Is it worth taking a little time each day to make sure a feeder is flowing?  Or should the easier approach be taken and grind feed at 1000 to 1200 microns which flows freely through bins and feeders?  To answer these questions, compare the effect on feed efficiency of 800 vs. 1100 microns by using the following equation which was developed in university trials involving finishing pigs from 120 to 240 pounds. 

Feed/Gain = Particle Size x 0.000415175 + 3.066333


Particle Size, Microns




Differences 800 vs. 1100

Feed/GainTotal Feed Required   Per 120 Lb Gain, Lb

Diet Cost, $/Ton

Diet Cost/Pig, $
















By reducing particle size from 1100 to 800 microns, feed efficiency was improved by 0.12, and feed required per pig was reduced by 14.4 pounds.  The savings in diet cost per finishing pigs was $1.26!  Keep in mind that these projections were from 120 to 240 pounds and thus do not include the cost savings in growing pigs and those fed out to heavier weights.  Based on the finishing numbers alone, an operation producing 60,000 pigs a year would save over $75,000. 

Given the higher prices for corn, in recent years, it would be imperative that we grind corn finer to increase the bottom line to swine producers.