The length of forage particles is considered as an important issue in feeding ruminants. Three Pennsylvania particle separator boxes are shown in the figure, which consists of 4 floors and the bottom cage has no holes and collects the particles that pass through the top three floors. There are three types of boxes:

A three-box system, a 4-box system with a third box having 1100 micron holes, or a 4-box system with 4000 micron holes. The practical recommendations of each system are given below.

3 or 4-box systems contain holes, the largest of which are located in the upper boxes. The way to work with them is that fodder or TMR should be poured into the upper box. Shake the separator 5 times and turn it a quarter turn. Repeat this 8 times and then weigh the remaining material on each sieve and the bottom of the box. The percentage of particles with different lengths can be determined numerically (based on wet weight).