Modification of the Penn State Forage and total mixed ration particle separator and the effects of moisture content on its measurements

The Penn State Particle Separator has led to widespread measurement of forage and total mixed ration (TMR) particle size. However, a large proportion of small particles may pass through both sieves when a TMR is analyzed, and field research has suggested that both shaking frequency and sample dry matter may affect the results. The objectives of this project were to test the effects of an additional sieve with a smaller aperture size, shaking frequency, and sample moisture content on results obtained. A sieve was constructed out of wire with a nominal size aperture of 1.18 mm. Samples of alfalfa haylage, corn silage, and a TMR were shaken at frequencies of 0.9, 1.1, and 1.6 Hz with a 17-cm stroke length. Reducing shaking frequency to 0.9 Hz resulted in more material being retained on the 19.0-mm sieve for all sample types, increasing the geometric mean. Increasing frequency to 1.6 Hz did not affect the geometric mean, but did result in a greater amount of corn silage falling through the 1.18-mm sieve. For alfalfa haylage, moisture content between 57.4 and 35.6% did not affect results; however, for corn silage, less moisture increased the percentage of particles less than 1.18 mm and decreased the geometric mean. For both sample types, further drying caused a greater proportion of small particles and a smaller geometric mean. We suggest using a third sieve and shaking at 1.1 Hz or greater with a stroke length of 17 cm when using the Penn State Particle Separator to analyze forage particle size.