Chop length affects both ensiling characteristics and forage quality. A short crop minimizes air infiltration into the silo, while a longer chop length increases effective fiber in the diet. Current recommendations are to harvest grass and alfalfa at a theoretical length-of-cut (TLC) of 3/8 to 1/2 inch and corn at a TLC of 1/2 to 3/4 inch. Remember that corn harvested for silage at greater than 30% DM should be processed to maximize utilization by the animal.

NASCO®’s Penn State Forage Particle Separator

Actual chop length can be monitored in the field by using NASCO®’s Penn State Forage Particle Separator (Figure 1). Forages are separated into three fractions (Figure 2):

• Particles greater than 3/4 inch
• Particles between 5/16 and 3/4 inch
• Particles less than 5/16 inch

Ideally, after sieving the material should be distributed:

• 25-50%: less than 5/16 inch
• 40-50%: between 5/16 and 3/4 inch
• 10-25%: greater than 3/4 inch

Using the Penn State Forage Particle Separator:

http://www.das.psu.edu/dairynutrition/forages/particle